Merge text.love

14 files changed, 343 insertions, 391 deletions

diff --git a/app.lua b/app.lua
index 627a438..263518c 100644
--- a/app.lua
+++ b/app.lua
@@ -130,6 +130,8 @@ function App.run_tests()
     end
   end
   table.sort(sorted_names)
+--?   App.initialize_for_test() -- debug: run a single test at a time like these 2 lines
+--?   test_click_below_all_lines()
   for _,name in ipairs(sorted_names) do
     App.initialize_for_test()
 --?     print('=== '..name)
@@ -404,9 +406,10 @@ end
 -- prepend file/line/test
 function prepend_debug_info_to_test_failure(test_name, err)
   local err_without_line_number = err:gsub('^[^:]*:[^:]*: ', '')
-  local stack_trace = debug.traceback('', --[[stack frame]]5)
+  local stack_trace = debug.traceback('', --[[stack frame]]5)  -- most likely to be useful, but set to 0 for a complete stack trace
   local file_and_line_number = stack_trace:gsub('stack traceback:\n', ''):gsub(': .*', '')
   local full_error = file_and_line_number..':'..test_name..' -- '..err_without_line_number
+  -- uncomment this line for a complete stack trace
 --?   local full_error = file_and_line_number..':'..test_name..' -- '..err_without_line_number..'\t\t'..stack_trace:gsub('\n', '\n\t\t')
   table.insert(Test_errors, full_error)
 end
diff --git a/drawing.lua b/drawing.lua
index 246c7ae..92e3d5f 100644
--- a/drawing.lua
+++ b/drawing.lua
@@ -6,16 +6,15 @@ require 'drawing_tests'
 -- into 256 parts.
 function Drawing.draw(State, line_index, y)
   local line = State.lines[line_index]
-  local line_cache = State.line_cache[line_index]
-  line_cache.starty = y
   local pmx,pmy = App.mouse_x(), App.mouse_y()
-  if pmx < State.right and pmy > line_cache.starty and pmy < line_cache.starty+Drawing.pixels(line.h, State.width) then
+  local starty = Text.starty(State, line_index)
+  if pmx < State.right and pmy > starty and pmy < starty+Drawing.pixels(line.h, State.width) then
     App.color(Icon_color)
-    love.graphics.rectangle('line', State.left,line_cache.starty, State.width,Drawing.pixels(line.h, State.width))
+    love.graphics.rectangle('line', State.left,starty, State.width,Drawing.pixels(line.h, State.width))
     if icon[State.current_drawing_mode] then
-      icon[State.current_drawing_mode](State.right-22, line_cache.starty+4)
+      icon[State.current_drawing_mode](State.right-22, starty+4)
     else
-      icon[State.previous_drawing_mode](State.right-22, line_cache.starty+4)
+      icon[State.previous_drawing_mode](State.right-22, starty+4)
     end
 
     if App.mouse_down(1) and love.keyboard.isDown('h') then
@@ -30,7 +29,7 @@ function Drawing.draw(State, line_index, y)
   end
 
   local mx = Drawing.coord(pmx-State.left, State.width)
-  local my = Drawing.coord(pmy-line_cache.starty, State.width)
+  local my = Drawing.coord(pmy-starty, State.width)
 
   for _,shape in ipairs(line.shapes) do
     if geom.on_shape(mx,my, line, shape) then
@@ -38,11 +37,11 @@ function Drawing.draw(State, line_index, y)
     else
       App.color(Stroke_color)
     end
-    Drawing.draw_shape(line, shape, line_cache.starty, State.left,State.right)
+    Drawing.draw_shape(line, shape, starty, State.left,State.right)
   end
 
   local function px(x) return Drawing.pixels(x, State.width)+State.left end
-  local function py(y) return Drawing.pixels(y, State.width)+line_cache.starty end
+  local function py(y) return Drawing.pixels(y, State.width)+starty end
   for i,p in ipairs(line.points) do
     if p.deleted == nil then
       if Drawing.near(p, mx,my, State.width) then
@@ -71,7 +70,7 @@ function Drawing.draw(State, line_index, y)
     end
   end
   App.color(Current_stroke_color)
-  Drawing.draw_pending_shape(line, line_cache.starty, State.left,State.right)
+  Drawing.draw_pending_shape(line, starty, State.left,State.right)
 end
 
 function Drawing.draw_shape(drawing, shape, top, left,right)
@@ -209,17 +208,24 @@ function Drawing.draw_pending_shape(drawing, top, left,right)
   end
 end
 
-function Drawing.in_drawing(drawing, line_cache, x,y, left,right)
-  if line_cache.starty == nil then return false end  -- outside current page
+function Drawing.in_current_drawing(State, x,y, left,right)
+  return Drawing.in_drawing(State, State.lines.current_drawing_index, x,y, left,right)
+end
+
+function Drawing.in_drawing(State, line_index, x,y, left,right)
+  assert(State.lines[line_index].mode == 'drawing')
+  local starty = Text.starty(State, line_index)
+  if starty == nil then return false end  -- outside current page
+  local drawing = State.lines[line_index]
   local width = right-left
-  return y >= line_cache.starty and y < line_cache.starty + Drawing.pixels(drawing.h, width) and x >= left and x < right
+  return y >= starty and y < starty + Drawing.pixels(drawing.h, width) and x >= left and x < right
 end
 
 function Drawing.mouse_press(State, drawing_index, x,y, mouse_button)
   local drawing = State.lines[drawing_index]
-  local line_cache = State.line_cache[drawing_index]
+  local starty = Text.starty(State, drawing_index)
   local cx = Drawing.coord(x-State.left, State.width)
-  local cy = Drawing.coord(y-line_cache.starty, State.width)
+  local cy = Drawing.coord(y-starty, State.width)
   if State.current_drawing_mode == 'freehand' then
     drawing.pending = {mode=State.current_drawing_mode, points={{x=cx, y=cy}}}
   elseif State.current_drawing_mode == 'line' or State.current_drawing_mode == 'manhattan' then
@@ -244,8 +250,8 @@ end
 function Drawing.update(State)
   if State.lines.current_drawing == nil then return end
   local drawing = State.lines.current_drawing
-  local line_cache = State.line_cache[State.lines.current_drawing_index]
-  if line_cache.starty == nil then
+  local starty = Text.starty(State, State.lines.current_drawing_index)
+  if starty == nil then
     -- some event cleared starty just this frame
     -- draw in this frame will soon set starty
     -- just skip this frame
@@ -254,9 +260,9 @@ function Drawing.update(State)
   assert(drawing.mode == 'drawing', 'Drawing.update: line is not a drawing')
   local pmx, pmy = App.mouse_x(), App.mouse_y()
   local mx = Drawing.coord(pmx-State.left, State.width)
-  local my = Drawing.coord(pmy-line_cache.starty, State.width)
+  local my = Drawing.coord(pmy-starty, State.width)
   if App.mouse_down(1) then
-    if Drawing.in_drawing(drawing, line_cache, pmx,pmy, State.left,State.right) then
+    if Drawing.in_current_drawing(State, pmx,pmy, State.left,State.right) then
       if drawing.pending.mode == 'freehand' then
         table.insert(drawing.pending.points, {x=mx, y=my})
       elseif drawing.pending.mode == 'move' then
@@ -266,7 +272,7 @@ function Drawing.update(State)
       end
     end
   elseif State.current_drawing_mode == 'move' then
-    if Drawing.in_drawing(drawing, line_cache, pmx, pmy, State.left,State.right) then
+    if Drawing.in_current_drawing(State, pmx, pmy, State.left,State.right) then
       drawing.pending.target_point.x = mx
       drawing.pending.target_point.y = my
       Drawing.relax_constraints(drawing, drawing.pending.target_point_index)
@@ -304,7 +310,7 @@ function Drawing.mouse_release(State, x,y, mouse_button)
     end
   elseif State.lines.current_drawing then
     local drawing = State.lines.current_drawing
-    local line_cache = State.line_cache[State.lines.current_drawing_index]
+    local starty = Text.starty(State, State.lines.current_drawing_index)
     if drawing.pending then
       if drawing.pending.mode == nil then
         -- nothing pending
@@ -313,14 +319,14 @@ function Drawing.mouse_release(State, x,y, mouse_button)
         Drawing.smoothen(drawing.pending)
         table.insert(drawing.shapes, drawing.pending)
       elseif drawing.pending.mode == 'line' then
-        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
+        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-starty, State.width)
         if mx >= 0 and mx < 256 and my >= 0 and my < drawing.h then
           drawing.pending.p2 = Drawing.find_or_insert_point(drawing.points, mx,my, State.width)
           table.insert(drawing.shapes, drawing.pending)
         end
       elseif drawing.pending.mode == 'manhattan' then
         local p1 = drawing.points[drawing.pending.p1]
-        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
+        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-starty, State.width)
         if mx >= 0 and mx < 256 and my >= 0 and my < drawing.h then
           if math.abs(mx-p1.x) > math.abs(my-p1.y) then
             drawing.pending.p2 = Drawing.find_or_insert_point(drawing.points, mx, p1.y, State.width)
@@ -328,11 +334,11 @@ function Drawing.mouse_release(State, x,y, mouse_button)
             drawing.pending.p2 = Drawing.find_or_insert_point(drawing.points, p1.x, my, State.width)
           end
           local p2 = drawing.points[drawing.pending.p2]
-          App.mouse_move(State.left+Drawing.pixels(p2.x, State.width), line_cache.starty+Drawing.pixels(p2.y, State.width))
+          App.mouse_move(State.left+Drawing.pixels(p2.x, State.width), starty+Drawing.pixels(p2.y, State.width))
           table.insert(drawing.shapes, drawing.pending)
         end
       elseif drawing.pending.mode == 'polygon' then
-        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
+        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-starty, State.width)
         if mx >= 0 and mx < 256 and my >= 0 and my < drawing.h then
           table.insert(drawing.pending.vertices, Drawing.find_or_insert_point(drawing.points, mx,my, State.width))
           table.insert(drawing.shapes, drawing.pending)
@@ -340,7 +346,7 @@ function Drawing.mouse_release(State, x,y, mouse_button)
       elseif drawing.pending.mode == 'rectangle' then
         assert(#drawing.pending.vertices <= 2, 'Drawing.mouse_release: rectangle has too many pending vertices')
         if #drawing.pending.vertices == 2 then
-          local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
+          local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-starty, State.width)
           if mx >= 0 and mx < 256 and my >= 0 and my < drawing.h then
             local first = drawing.points[drawing.pending.vertices[1]]
             local second = drawing.points[drawing.pending.vertices[2]]
@@ -355,7 +361,7 @@ function Drawing.mouse_release(State, x,y, mouse_button)
       elseif drawing.pending.mode == 'square' then
         assert(#drawing.pending.vertices <= 2, 'Drawing.mouse_release: square has too many pending vertices')
         if #drawing.pending.vertices == 2 then
-          local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
+          local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-starty, State.width)
           if mx >= 0 and mx < 256 and my >= 0 and my < drawing.h then
             local first = drawing.points[drawing.pending.vertices[1]]
             local second = drawing.points[drawing.pending.vertices[2]]
@@ -366,14 +372,14 @@ function Drawing.mouse_release(State, x,y, mouse_button)
           end
         end
       elseif drawing.pending.mode == 'circle' then
-        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
+        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-starty, State.width)
         if mx >= 0 and mx < 256 and my >= 0 and my < drawing.h then
           local center = drawing.points[drawing.pending.center]
           drawing.pending.radius = round(geom.dist(center.x,center.y, mx,my))
           table.insert(drawing.shapes, drawing.pending)
         end
       elseif drawing.pending.mode == 'arc' then
-        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
+        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-starty, State.width)
         if mx >= 0 and mx < 256 and my >= 0 and my < drawing.h then
           local center = drawing.points[drawing.pending.center]
           drawing.pending.end_angle = geom.angle_with_hint(center.x,center.y, mx,my, drawing.pending.end_angle)
@@ -477,13 +483,15 @@ function Drawing.keychord_press(State, chord)
     end
     drawing.pending.mode = 'square'
   elseif App.mouse_down(1) and chord == 'p' and State.current_drawing_mode == 'polygon' then
-    local _,drawing,line_cache = Drawing.current_drawing(State)
-    local mx,my = Drawing.coord(App.mouse_x()-State.left, State.width), Drawing.coord(App.mouse_y()-line_cache.starty, State.width)
+    local drawing_index,drawing = Drawing.current_drawing(State)
+    local starty = Text.starty(State, drawing_index)
+    local mx,my = Drawing.coord(App.mouse_x()-State.left, State.width), Drawing.coord(App.mouse_y()-starty, State.width)
     local j = Drawing.find_or_insert_point(drawing.points, mx,my, State.width)
     table.insert(drawing.pending.vertices, j)
   elseif App.mouse_down(1) and chord == 'p' and (State.current_drawing_mode == 'rectangle' or State.current_drawing_mode == 'square') then
-    local _,drawing,line_cache = Drawing.current_drawing(State)
-    local mx,my = Drawing.coord(App.mouse_x()-State.left, State.width), Drawing.coord(App.mouse_y()-line_cache.starty, State.width)
+    local drawing_index,drawing = Drawing.current_drawing(State)
+    local starty = Text.starty(State, drawing_index)
+    local mx,my = Drawing.coord(App.mouse_x()-State.left, State.width), Drawing.coord(App.mouse_y()-starty, State.width)
     local j = Drawing.find_or_insert_point(drawing.points, mx,my, State.width)
     while #drawing.pending.vertices >= 2 do
       table.remove(drawing.pending.vertices)
@@ -492,9 +500,10 @@ function Drawing.keychord_press(State, chord)
   elseif chord == 'C-o' and not App.mouse_down(1) then
     State.current_drawing_mode = 'circle'
   elseif App.mouse_down(1) and chord == 'a' and State.current_drawing_mode == 'circle' then
-    local _,drawing,line_cache = Drawing.current_drawing(State)
+    local drawing_index,drawing = Drawing.current_drawing(State)
+    local starty = Text.starty(State, drawing_index)
     drawing.pending.mode = 'arc'
-    local mx,my = Drawing.coord(App.mouse_x()-State.left, State.width), Drawing.coord(App.mouse_y()-line_cache.starty, State.width)
+    local mx,my = Drawing.coord(App.mouse_x()-State.left, State.width), Drawing.coord(App.mouse_y()-starty, State.width)
     local center = drawing.points[drawing.pending.center]
     drawing.pending.radius = round(geom.dist(center.x,center.y, mx,my))
     drawing.pending.start_angle = geom.angle(center.x,center.y, mx,my)
@@ -510,7 +519,7 @@ function Drawing.keychord_press(State, chord)
     end
     drawing.pending.mode = 'circle'
   elseif chord == 'C-u' and not App.mouse_down(1) then
-    local drawing_index,drawing,line_cache,i,p = Drawing.select_point_at_mouse(State)
+    local drawing_index,drawing,_,i,p = Drawing.select_point_at_mouse(State)
     if drawing then
       if State.previous_drawing_mode == nil then
         State.previous_drawing_mode = State.current_drawing_mode
@@ -521,7 +530,7 @@ function Drawing.keychord_press(State, chord)
       State.lines.current_drawing = drawing
     end
   elseif chord == 'C-n' and not App.mouse_down(1) then
-    local drawing_index,drawing,line_cache,point_index,p = Drawing.select_point_at_mouse(State)
+    local drawing_index,drawing,_,point_index,p = Drawing.select_point_at_mouse(State)
     if drawing then
       if State.previous_drawing_mode == nil then
         -- don't clobber
@@ -619,9 +628,8 @@ function Drawing.current_drawing(State)
   local x, y = App.mouse_x(), App.mouse_y()
   for drawing_index,drawing in ipairs(State.lines) do
     if drawing.mode == 'drawing' then
-      local line_cache = State.line_cache[drawing_index]
-      if Drawing.in_drawing(drawing, line_cache, x,y, State.left,State.right) then
-        return drawing_index,drawing,line_cache
+      if Drawing.in_drawing(State, drawing_index, x,y, State.left,State.right) then
+        return drawing_index,drawing
       end
     end
   end
@@ -632,12 +640,12 @@ function Drawing.select_shape_at_mouse(State)
   for drawing_index,drawing in ipairs(State.lines) do
     if drawing.mode == 'drawing' then
       local x, y = App.mouse_x(), App.mouse_y()
-      local line_cache = State.line_cache[drawing_index]
-      if Drawing.in_drawing(drawing, line_cache, x,y, State.left,State.right) then
-        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
+      local starty = Text.starty(State, drawing_index)
+      if Drawing.in_drawing(State, drawing_index, x,y, State.left,State.right) then
+        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-starty, State.width)
         for i,shape in ipairs(drawing.shapes) do
           if geom.on_shape(mx,my, drawing, shape) then
-            return drawing,line_cache,i,shape
+            return drawing,starty,i,shape
           end
         end
       end
@@ -649,12 +657,12 @@ function Drawing.select_point_at_mouse(State)
   for drawing_index,drawing in ipairs(State.lines) do
     if drawing.mode == 'drawing' then
       local x, y = App.mouse_x(), App.mouse_y()
-      local line_cache = State.line_cache[drawing_index]
-      if Drawing.in_drawing(drawing, line_cache, x,y, State.left,State.right) then
-        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-line_cache.starty, State.width)
+      local starty = Text.starty(State, drawing_index)
+      if Drawing.in_drawing(State, drawing_index, x,y, State.left,State.right) then
+        local mx,my = Drawing.coord(x-State.left, State.width), Drawing.coord(y-starty, State.width)
         for i,point in ipairs(drawing.points) do
           if Drawing.near(point, mx,my, State.width) then
-            return drawing_index,drawing,line_cache,i,point
+            return drawing_index,drawing,starty,i,point
           end
         end
       end
@@ -666,8 +674,7 @@ function Drawing.select_drawing_at_mouse(State)
   for drawing_index,drawing in ipairs(State.lines) do
     if drawing.mode == 'drawing' then
       local x, y = App.mouse_x(), App.mouse_y()
-      local line_cache = State.line_cache[drawing_index]
-      if Drawing.in_drawing(drawing, line_cache, x,y, State.left,State.right) then
+      if Drawing.in_drawing(State, drawing_index, x,y, State.left,State.right) then
         return drawing
       end
     end
diff --git a/drawing_tests.lua b/drawing_tests.lua
index ede25f0..3484436 100644
--- a/drawing_tests.lua
+++ b/drawing_tests.lua
@@ -3,7 +3,7 @@
 -- of specific shapes. In particular, no tests of freehand drawings.
 
 function test_creating_drawing_saves()
-  App.screen.init{width=120, height=60}
+  App.screen.init{width=800, height=600}
   Editor_state = edit.initialize_test_state()
   Editor_state.filename = 'foo'
   Editor_state.lines = load_array{}
@@ -32,7 +32,7 @@ function test_draw_line()
   edit.draw(Editor_state)
   check_eq(#Editor_state.lines, 2, 'baseline/#lines')
   check_eq(Editor_state.lines[1].mode, 'drawing', 'baseline/mode')
-  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'baseline/y')
+  check_eq(Text.starty(Editor_state, 1), Editor_state.top+Drawing_padding_top, 'baseline/y')
   check_eq(Editor_state.lines[1].h, 128, 'baseline/y')
   check_eq(#Editor_state.lines[1].shapes, 0, 'baseline/#shapes')
   -- draw a line
@@ -77,7 +77,7 @@ function test_draw_horizontal_line()
   edit.draw(Editor_state)
   check_eq(#Editor_state.lines, 2, 'baseline/#lines')
   check_eq(Editor_state.lines[1].mode, 'drawing', 'baseline/mode')
-  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'baseline/y')
+  check_eq(Text.starty(Editor_state, 1), Editor_state.top+Drawing_padding_top, 'baseline/y')
   check_eq(Editor_state.lines[1].h, 128, 'baseline/y')
   check_eq(#Editor_state.lines[1].shapes, 0, 'baseline/#shapes')
   -- draw a line that is more horizontal than vertical
@@ -105,7 +105,7 @@ function test_draw_circle()
   edit.draw(Editor_state)
   check_eq(#Editor_state.lines, 2, 'baseline/#lines')
   check_eq(Editor_state.lines[1].mode, 'drawing', 'baseline/mode')
-  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'baseline/y')
+  check_eq(Text.starty(Editor_state, 1), Editor_state.top+Drawing_padding_top, 'baseline/y')
   check_eq(Editor_state.lines[1].h, 128, 'baseline/y')
   check_eq(#Editor_state.lines[1].shapes, 0, 'baseline/#shapes')
   -- draw a circle
@@ -134,7 +134,7 @@ function test_cancel_stroke()
   edit.draw(Editor_state)
   check_eq(#Editor_state.lines, 2, 'baseline/#lines')
   check_eq(Editor_state.lines[1].mode, 'drawing', 'baseline/mode')
-  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'baseline/y')
+  check_eq(Text.starty(Editor_state, 1), Editor_state.top+Drawing_padding_top, 'baseline/y')
   check_eq(Editor_state.lines[1].h, 128, 'baseline/y')
   check_eq(#Editor_state.lines[1].shapes, 0, 'baseline/#shapes')
   -- start drawing a line
@@ -172,7 +172,7 @@ function test_draw_circle_mid_stroke()
   edit.draw(Editor_state)
   check_eq(#Editor_state.lines, 2, 'baseline/#lines')
   check_eq(Editor_state.lines[1].mode, 'drawing', 'baseline/mode')
-  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'baseline/y')
+  check_eq(Text.starty(Editor_state, 1), Editor_state.top+Drawing_padding_top, 'baseline/y')
   check_eq(Editor_state.lines[1].h, 128, 'baseline/y')
   check_eq(#Editor_state.lines[1].shapes, 0, 'baseline/#shapes')
   -- draw a circle
@@ -200,7 +200,7 @@ function test_draw_arc()
   edit.draw(Editor_state)
   check_eq(#Editor_state.lines, 2, 'baseline/#lines')
   check_eq(Editor_state.lines[1].mode, 'drawing', 'baseline/mode')
-  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'baseline/y')
+  check_eq(Text.starty(Editor_state, 1), Editor_state.top+Drawing_padding_top, 'baseline/y')
   check_eq(Editor_state.lines[1].h, 128, 'baseline/y')
   check_eq(#Editor_state.lines[1].shapes, 0, 'baseline/#shapes')
   -- draw an arc
@@ -231,7 +231,7 @@ function test_draw_polygon()
   check_eq(Editor_state.current_drawing_mode, 'line', 'baseline/drawing_mode')
   check_eq(#Editor_state.lines, 2, 'baseline/#lines')
   check_eq(Editor_state.lines[1].mode, 'drawing', 'baseline/mode')
-  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'baseline/y')
+  check_eq(Text.starty(Editor_state, 1), Editor_state.top+Drawing_padding_top, 'baseline/y')
   check_eq(Editor_state.lines[1].h, 128, 'baseline/y')
   check_eq(#Editor_state.lines[1].shapes, 0, 'baseline/#shapes')
   -- first point
@@ -269,7 +269,7 @@ function test_draw_rectangle()
   check_eq(Editor_state.current_drawing_mode, 'line', 'baseline/drawing_mode')
   check_eq(#Editor_state.lines, 2, 'baseline/#lines')
   check_eq(Editor_state.lines[1].mode, 'drawing', 'baseline/mode')
-  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'baseline/y')
+  check_eq(Text.starty(Editor_state, 1), Editor_state.top+Drawing_padding_top, 'baseline/y')
   check_eq(Editor_state.lines[1].h, 128, 'baseline/y')
   check_eq(#Editor_state.lines[1].shapes, 0, 'baseline/#shapes')
   -- first point
@@ -313,7 +313,7 @@ function test_draw_rectangle_intermediate()
   check_eq(Editor_state.current_drawing_mode, 'line', 'baseline/drawing_mode')
   check_eq(#Editor_state.lines, 2, 'baseline/#lines')
   check_eq(Editor_state.lines[1].mode, 'drawing', 'baseline/mode')
-  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'baseline/y')
+  check_eq(Text.starty(Editor_state, 1), Editor_state.top+Drawing_padding_top, 'baseline/y')
   check_eq(Editor_state.lines[1].h, 128, 'baseline/y')
   check_eq(#Editor_state.lines[1].shapes, 0, 'baseline/#shapes')
   -- first point
@@ -349,7 +349,7 @@ function test_draw_square()
   check_eq(Editor_state.current_drawing_mode, 'line', 'baseline/drawing_mode')
   check_eq(#Editor_state.lines, 2, 'baseline/#lines')
   check_eq(Editor_state.lines[1].mode, 'drawing', 'baseline/mode')
-  check_eq(Editor_state.line_cache[1].starty, Editor_state.top+Drawing_padding_top, 'baseline/y')
+  check_eq(Text.starty(Editor_state, 1), Editor_state.top+Drawing_padding_top, 'baseline/y')
   check_eq(Editor_state.lines[1].h, 128, 'baseline/y')
   check_eq(#Editor_state.lines[1].shapes, 0, 'baseline/#shapes')
   -- first point
diff --git a/edit.lua b/edit.lua
index 79a2fc3..6a7d708 100644
--- a/edit.lua
+++ b/edit.lua
@@ -19,7 +19,6 @@ function edit.initialize_state(top, left, right, font, font_height, line_height)
 
     -- rendering wrapped text lines needs some additional short-lived data per line:
     --   startpos, the index of data the line starts rendering from, can only be >1 for topmost line on screen
-    --   starty, the y coord in pixels the line starts rendering from
     --   fragments: snippets of the line guaranteed to not straddle screen lines
     --   screen_line_starting_pos: optional array of grapheme indices if it wraps over more than one screen line
     line_cache = {},
@@ -33,9 +32,10 @@ function edit.initialize_state(top, left, right, font, font_height, line_height)
     --
     -- Make sure these coordinates are never aliased, so that changing one causes
     -- action at a distance.
+    --
+    -- On lines that are drawings, pos will be nil.
     screen_top1 = {line=1, pos=1},  -- position of start of screen line at top of screen
-    cursor1 = {line=1, pos=1},  -- position of cursor
-    screen_bottom1 = {line=1, pos=1},  -- position of start of screen line at bottom of screen
+    cursor1 = {line=1, pos=1},  -- position of cursor; must be on a text line
 
     selection1 = {},
     -- some extra state to compute selection between mouse press and release
@@ -102,22 +102,19 @@ function edit.draw(State)
   State.cursor_x = nil
   State.cursor_y = nil
   local y = State.top
-  local screen_bottom1 = {line=nil, pos=nil}
 --?   print('== draw')
   for line_index = State.screen_top1.line,#State.lines do
     local line = State.lines[line_index]
 --?     print('draw:', y, line_index, line)
     if y + State.line_height > App.screen.height then break end
-    screen_bottom1.line = line_index
 --?     print('text.draw', y, line_index)
     local startpos = 1
     if line_index == State.screen_top1.line then
       startpos = State.screen_top1.pos
     end
-    y, screen_bottom1.pos = Text.draw(State, line_index, y, startpos)
+    y = Text.draw(State, line_index, y, startpos)
 --?     print('=> y', y)
   end
-  State.screen_bottom1 = screen_bottom1
   if State.search_term then
     Text.draw_search_bar(State)
   end
@@ -173,10 +170,7 @@ function edit.mouse_press(State, x,y, mouse_button)
   State.old_cursor1 = State.cursor1
   State.old_selection1 = State.selection1
   State.mousepress_shift = App.shift_down()
-  State.selection1 = {
-      line=State.screen_bottom1.line,
-      pos=Text.pos_at_end_of_screen_line(State, State.screen_bottom1),
-  }
+  State.selection1 = Text.final_text_loc_on_screen(State)
 end
 
 function edit.mouse_release(State, x,y, mouse_button)
@@ -202,7 +196,7 @@ function edit.mouse_release(State, x,y, mouse_button)
   end
 
   -- still here? mouse release is below all screen lines
-  State.cursor1.line, State.cursor1.pos = State.screen_bottom1.line, Text.pos_at_end_of_screen_line(State, State.screen_bottom1)
+  State.cursor1 = Text.final_text_loc_on_screen(State)
   edit.clean_up_mouse_press(State)
 --?   print_and_log(('edit.mouse_release: finally selection %s,%s cursor %d,%d'):format(tostring(State.selection1.line), tostring(State.selection1.pos), State.cursor1.line, State.cursor1.pos))
 end
@@ -228,7 +222,8 @@ function edit.mouse_wheel_move(State, dx,dy)
       Text.up(State)
     end
   elseif dy < 0 then
-    State.cursor1 = {line=State.screen_bottom1.line, pos=State.screen_bottom1.pos}
+    State.cursor1 = Text.screen_bottom1(State)
+    edit.put_cursor_on_next_text_line(State)
     for i=1,math.floor(-dy) do
       Text.down(State)
     end
@@ -252,7 +247,6 @@ function edit.keychord_press(State, chord, key)
     Text.delete_selection(State, State.left, State.right)
   end
   if State.search_term then
-    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
     if chord == 'escape' then
       State.search_term = nil
       State.cursor1 = State.search_backup.cursor
@@ -302,7 +296,6 @@ function edit.keychord_press(State, chord, key)
     end
   -- dispatch to text
   else
-    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
     Text.keychord_press(State, chord)
   end
 end
@@ -357,6 +350,7 @@ end
 function edit.run_after_mouse_click(State, x,y, mouse_button)
   App.fake_mouse_press(x,y, mouse_button)
   edit.mouse_press(State, x,y, mouse_button)
+  edit.draw(State)
   App.fake_mouse_release(x,y, mouse_button)
   edit.mouse_release(State, x,y, mouse_button)
   App.screen.contents = {}
diff --git a/help.lua b/help.lua
index 6f8633b..cc7a0c9 100644
--- a/help.lua
+++ b/help.lua
@@ -1,8 +1,8 @@
 function draw_help_without_mouse_pressed(State, drawing_index)
   local drawing = State.lines[drawing_index]
-  local line_cache = State.line_cache[drawing_index]
+  local starty = Text.starty(State, drawing_index)
   App.color(Help_color)
-  local y = line_cache.starty+10
+  local y = starty+10
   love.graphics.print("Things you can do:", State.left+30,y)
   y = y + State.line_height
   love.graphics.print("* Press the mouse button to start drawing a "..current_shape(State), State.left+30,y)
@@ -48,14 +48,14 @@ function draw_help_without_mouse_pressed(State, drawing_index)
   love.graphics.print("Press 'esc' now to hide this message", State.left+30,y)
   y = y + State.line_height
   App.color(Help_background_color)
-  love.graphics.rectangle('fill', State.left,line_cache.starty, State.width, math.max(Drawing.pixels(drawing.h, State.width),y-line_cache.starty))
+  love.graphics.rectangle('fill', State.left,starty, State.width, math.max(Drawing.pixels(drawing.h, State.width),y-starty))
 end
 
 function draw_help_with_mouse_pressed(State, drawing_index)
   local drawing = State.lines[drawing_index]
-  local line_cache = State.line_cache[drawing_index]
+  local starty = Text.starty(State, drawing_index)
   App.color(Help_color)
-  local y = line_cache.starty+10
+  local y = starty+10
   love.graphics.print("You're currently drawing a "..current_shape(State, drawing.pending), State.left+30,y)
   y = y + State.line_height
   love.graphics.print('Things you can do now:', State.left+30,y)
@@ -129,7 +129,7 @@ function draw_help_with_mouse_pressed(State, drawing_index)
     y = y + State.line_height
   end
   App.color(Help_background_color)
-  love.graphics.rectangle('fill', State.left,line_cache.starty, State.width, math.max(Drawing.pixels(drawing.h, State.width),y-line_cache.starty))
+  love.graphics.rectangle('fill', State.left,starty, State.width, math.max(Drawing.pixels(drawing.h, State.width),y-starty))
 end
 
 function current_shape(State, shape)
diff --git a/search.lua b/search.lua
index 54bab14..d3a5fea 100644
--- a/search.lua
+++ b/search.lua
@@ -62,7 +62,8 @@ function Text.search_next(State)
     State.screen_top1.line = State.search_backup.screen_top.line
     State.screen_top1.pos = State.search_backup.screen_top.pos
   end
-  if Text.lt1(State.cursor1, State.screen_top1) or Text.lt1(State.screen_bottom1, State.cursor1) then
+  local screen_bottom1 = Text.screen_bottom1(State)
+  if Text.lt1(State.cursor1, State.screen_top1) or Text.lt1(screen_bottom1, State.cursor1) then
     State.screen_top1.line = State.cursor1.line
     local pos = Text.pos_at_start_of_screen_line(State, State.cursor1)
     State.screen_top1.pos = pos
@@ -115,7 +116,8 @@ function Text.search_previous(State)
     State.screen_top1.line = State.search_backup.screen_top.line
     State.screen_top1.pos = State.search_backup.screen_top.pos
   end
-  if Text.lt1(State.cursor1, State.screen_top1) or Text.lt1(State.screen_bottom1, State.cursor1) then
+  local screen_bottom1 = Text.screen_bottom1(State)
+  if Text.lt1(State.cursor1, State.screen_top1) or Text.lt1(screen_bottom1, State.cursor1) then
     State.screen_top1.line = State.cursor1.line
     local pos = Text.pos_at_start_of_screen_line(State, State.cursor1)
     State.screen_top1.pos = pos
diff --git a/select.lua b/select.lua
index 79eeb82..2d0851a 100644
--- a/select.lua
+++ b/select.lua
@@ -69,7 +69,7 @@ end
 
 function Text.mouse_pos(State)
   local x,y = App.mouse_x(), App.mouse_y()
-  if y < State.line_cache[State.screen_top1.line].starty then
+  if y < State.top then
     return State.screen_top1.line, State.screen_top1.pos
   end
   for line_index,line in ipairs(State.lines) do
@@ -77,7 +77,8 @@ function Text.mouse_pos(State)
       return line_index, Text.to_pos_on_line(State, line_index, x,y)
     end
   end
-  return State.screen_bottom1.line, Text.pos_at_end_of_screen_line(State, State.screen_bottom1)
+  local screen_bottom1 = Text.screen_bottom1(State)
+  return screen_bottom1.line, Text.pos_at_end_of_screen_line(State, screen_bottom1)
 end
 
 function Text.selection(State)
diff --git a/source.lua b/source.lua
index 9bc400e..7eec594 100644
--- a/source.lua
+++ b/source.lua
@@ -307,7 +307,6 @@ function source.mouse_press(x,y, mouse_button)
       return
     end
     log_browser.mouse_press(Log_browser_state, x,y, mouse_button)
-    for _,line_cache in ipairs(Editor_state.line_cache) do line_cache.starty = nil end  -- just in case we scroll
   end
 end
 
diff --git a/source_edit.lua b/source_edit.lua
index e376537..5351857 100644
--- a/source_edit.lua
+++ b/source_edit.lua
@@ -33,7 +33,6 @@ function edit.initialize_state(top, left, right, font, font_height, line_height)
     --    string data,
     -- a drawing is a table with:
     --    mode = 'drawing'
-    --    a (y) coord in pixels (updated while painting screen),
     --    a (h)eight,
     --    an array of points, and
     --    an array of shapes
@@ -54,7 +53,6 @@ function edit.initialize_state(top, left, right, font, font_height, line_height)
 
     -- rendering wrapped text lines needs some additional short-lived data per line:
     --   startpos, the index of data the line starts rendering from, can only be >1 for topmost line on screen
-    --   starty, the y coord in pixels the line starts rendering from
     --   fragments: snippets of the line guaranteed to not straddle screen lines
     --   screen_line_starting_pos: optional array of grapheme indices if it wraps over more than one screen line
     line_cache = {},
@@ -68,9 +66,10 @@ function edit.initialize_state(top, left, right, font, font_height, line_height)
     --
     -- Make sure these coordinates are never aliased, so that changing one causes
     -- action at a distance.
+    --
+    -- On lines that are drawings, pos will be nil.
     screen_top1 = {line=1, pos=1},  -- position of start of screen line at top of screen
-    cursor1 = {line=1, pos=1},  -- position of cursor
-    screen_bottom1 = {line=1, pos=1},  -- position of start of screen line at bottom of screen
+    cursor1 = {line=1, pos=1},  -- position of cursor; must be on a text line
 
     selection1 = {},
     -- some extra state to compute selection between mouse press and release
@@ -165,13 +164,11 @@ function edit.draw(State, hide_cursor, show_line_numbers)
   State.cursor_x = nil
   State.cursor_y = nil
   local y = State.top
-  local screen_bottom1 = {line=nil, pos=nil}
 --?   print('== draw')
   for line_index = State.screen_top1.line,#State.lines do
     local line = State.lines[line_index]
 --?     print('draw:', y, line_index, line)
     if y + State.line_height > App.screen.height then break end
-    screen_bottom1.line = line_index
     if line.mode == 'text' then
 --?       print('text.draw', y, line_index)
       local startpos = 1
@@ -198,7 +195,7 @@ function edit.draw(State, hide_cursor, show_line_numbers)
                      end,
         })
       end
-      y, screen_bottom1.pos = Text.draw(State, line_index, y, startpos, hide_cursor, show_line_numbers)
+      y = Text.draw(State, line_index, y, startpos, hide_cursor, show_line_numbers)
 --?       print('=> y', y)
     elseif line.mode == 'drawing' then
       y = y+Drawing_padding_top
@@ -208,7 +205,6 @@ function edit.draw(State, hide_cursor, show_line_numbers)
       assert(false, ('unknown line mode %s'):format(line.mode))
     end
   end
-  State.screen_bottom1 = screen_bottom1
   if State.search_term then
     Text.draw_search_bar(State)
   end
@@ -281,8 +277,7 @@ function edit.mouse_press(State, x,y, mouse_button)
         return
       end
     elseif line.mode == 'drawing' then
-      local line_cache = State.line_cache[line_index]
-      if Drawing.in_drawing(line, line_cache, x, y, State.left,State.right) then
+      if Drawing.in_drawing(State, line_index, x, y, State.left,State.right) then
         State.lines.current_drawing_index = line_index
         State.lines.current_drawing = line
         Drawing.before = snapshot(State, line_index)
@@ -296,10 +291,7 @@ function edit.mouse_press(State, x,y, mouse_button)
   State.old_cursor1 = State.cursor1
   State.old_selection1 = State.selection1
   State.mousepress_shift = App.shift_down()
-  State.selection1 = {
-      line=State.screen_bottom1.line,
-      pos=Text.pos_at_end_of_screen_line(State, State.screen_bottom1),
-  }
+  State.selection1 = Text.final_text_loc_on_screen(State)
 end
 
 function edit.mouse_release(State, x,y, mouse_button)
@@ -337,7 +329,7 @@ function edit.mouse_release(State, x,y, mouse_button)
     end
 
     -- still here? mouse release is below all screen lines
-    State.cursor1.line, State.cursor1.pos = State.screen_bottom1.line, Text.pos_at_end_of_screen_line(State, State.screen_bottom1)
+    State.cursor1 = Text.final_text_loc_on_screen(State)
     edit.clean_up_mouse_press(State)
 --?     print_and_log(('edit.mouse_release: finally selection %s,%s cursor %d,%d'):format(tostring(State.selection1.line), tostring(State.selection1.pos), State.cursor1.line, State.cursor1.pos))
   end
@@ -365,7 +357,7 @@ function edit.mouse_wheel_move(State, dx,dy)
       Text.up(State)
     end
   elseif dy < 0 then
-    State.cursor1 = {line=State.screen_bottom1.line, pos=State.screen_bottom1.pos}
+    State.cursor1 = Text.screen_bottom1(State)
     edit.put_cursor_on_next_text_line(State)
     for i=1,math.floor(-dy) do
       Text.down(State)
@@ -399,11 +391,10 @@ function edit.keychord_press(State, chord, key)
       -- printable character created using shift key => delete selection
       -- (we're not creating any ctrl-shift- or alt-shift- combinations using regular/printable keys)
       (not App.shift_down() or utf8.len(key) == 1) and
-      chord ~= 'C-a' and chord ~= 'C-c' and chord ~= 'C-x' and chord ~= 'backspace' and chord ~= 'delete' and chord ~= 'C-z' and chord ~= 'C-y' and not App.is_cursor_movement(chord) then
+      chord ~= 'C-a' and chord ~= 'C-c' and chord ~= 'C-x' and chord ~= 'backspace' and chord ~= 'delete' and chord ~= 'C-z' and chord ~= 'C-y' and not App.is_cursor_movement(key) then
     Text.delete_selection(State, State.left, State.right)
   end
   if State.search_term then
-    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
     if chord == 'escape' then
       State.search_term = nil
       State.cursor1 = State.search_backup.cursor
@@ -508,7 +499,6 @@ function edit.keychord_press(State, chord, key)
     record_undo_event(State, {before=before, after=snapshot(State, before_line, State.cursor1.line)})
   -- dispatch to drawing or text
   elseif App.mouse_down(1) or chord:sub(1,2) == 'C-' then
-    -- DON'T reset line_cache.starty here
     local drawing_index, drawing = Drawing.current_drawing(State)
     if drawing_index then
       local before = snapshot(State, drawing_index)
@@ -545,7 +535,6 @@ function edit.keychord_press(State, chord, key)
     end
     schedule_save(State)
   else
-    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
     Text.keychord_press(State, chord)
   end
 end
@@ -600,6 +589,7 @@ end
 function edit.run_after_mouse_click(State, x,y, mouse_button)
   App.fake_mouse_press(x,y, mouse_button)
   edit.mouse_press(State, x,y, mouse_button)
+  edit.draw(State)
   App.fake_mouse_release(x,y, mouse_button)
   edit.mouse_release(State, x,y, mouse_button)
   App.screen.contents = {}
diff --git a/source_select.lua b/source_select.lua
index 6e21c7b..b67dd16 100644
--- a/source_select.lua
+++ b/source_select.lua
@@ -69,7 +69,7 @@ end
 
 function Text.mouse_pos(State)
   local x,y = App.mouse_x(), App.mouse_y()
-  if y < State.line_cache[State.screen_top1.line].starty then
+  if y < State.top then
     return State.screen_top1.line, State.screen_top1.pos
   end
   for line_index,line in ipairs(State.lines) do
@@ -79,7 +79,8 @@ function Text.mouse_pos(State)
       end
     end
   end
-  return State.screen_bottom1.line, Text.pos_at_end_of_screen_line(State, State.screen_bottom1)
+  local screen_bottom1 = Text.screen_bottom1(State)
+  return screen_bottom1.line, Text.pos_at_end_of_screen_line(State, screen_bottom1)
 end
 
 function Text.cut_selection(State)
diff --git a/source_text.lua b/source_text.lua
index 7c1838c..6e0c4f9 100644
--- a/source_text.lua
+++ b/source_text.lua
@@ -2,14 +2,12 @@
 Text = {}
 
 -- draw a line starting from startpos to screen at y between State.left and State.right
--- return y for the next line, and position of start of final screen line drawn
+-- return y for the next line
 function Text.draw(State, line_index, y, startpos, hide_cursor, show_line_numbers)
   local line = State.lines[line_index]
   local line_cache = State.line_cache[line_index]
-  line_cache.starty = y
   line_cache.startpos = startpos
   -- wrap long lines
-  local final_screen_line_starting_pos = startpos  -- track value to return
   Text.populate_screen_line_starting_pos(State, line_index)
   Text.populate_link_offsets(State, line_index)
   if show_line_numbers then
@@ -24,7 +22,6 @@ function Text.draw(State, line_index, y, startpos, hide_cursor, show_line_number
       -- render nothing
 --?       print('skipping', screen_line)
     else
-      final_screen_line_starting_pos = pos
       local screen_line = Text.screen_line(line, line_cache, i)
 --?       print('text.draw:', screen_line, 'at', line_index,pos, 'after', x,y)
       local frag_len = utf8.len(screen_line)
@@ -84,7 +81,7 @@ function Text.draw(State, line_index, y, startpos, hide_cursor, show_line_number
       end
     end
   end
-  return y, final_screen_line_starting_pos
+  return y
 end
 
 function Text.screen_line(line, line_cache, i)
@@ -208,7 +205,7 @@ function Text.text_input(State, t)
     end
   end
   local before = snapshot(State, State.cursor1.line)
---?   print(State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
+--?   print(State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos)
   Text.insert_at_cursor(State, t)
   if State.cursor_y > App.screen.height - State.line_height then
     Text.populate_screen_line_starting_pos(State, State.cursor1.line)
@@ -241,12 +238,12 @@ function Text.keychord_press(State, chord)
     record_undo_event(State, {before=before, after=snapshot(State, before_line, State.cursor1.line)})
   elseif chord == 'tab' then
     local before = snapshot(State, State.cursor1.line)
---?     print(State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
+--?     print(State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos)
     Text.insert_at_cursor(State, '\t')
     if State.cursor_y > App.screen.height - State.line_height then
       Text.populate_screen_line_starting_pos(State, State.cursor1.line)
       Text.snap_cursor_to_bottom_of_screen(State, State.left, State.right)
---?       print('=>', State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
+--?       print('=>', State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos)
     end
     schedule_save(State)
     record_undo_event(State, {before=before, after=snapshot(State, State.cursor1.line)})
@@ -427,37 +424,79 @@ function Text.insert_return(State)
 end
 
 function Text.pageup(State)
---?   print('pageup')
+  State.screen_top1 = Text.previous_screen_top1(State)
+  State.cursor1 = {line=State.screen_top1.line, pos=State.screen_top1.pos}
+  Text.move_cursor_down_to_next_text_line_while_scrolling_again_if_necessary(State)
+  Text.redraw_all(State)  -- if we're scrolling, reclaim all fragments to avoid memory leaks
+end
+
+-- return the top y coordinate of a given line_index,
+-- or nil if no part of it is on screen
+function Text.starty(State, line_index)
+  -- duplicate some logic from love.draw
+  -- does not modify State (except to populate line_cache)
+  if line_index < State.screen_top1.line then return end
+  local loc2 = Text.to2(State, State.screen_top1)
+  local y = State.top
+  while true do
+    if State.lines[loc2.line].mode == 'drawing' then
+      y = y + Drawing_padding_top
+    end
+    if loc2.line == line_index then return y end
+    if State.lines[loc2.line].mode == 'text' then
+      y = y + State.line_height
+    elseif State.lines[loc2.line].mode == 'drawing' then
+      y = y + Drawing.pixels(State.lines[loc2.line].h, State.width) + Drawing_padding_bottom
+    end
+    if y + State.line_height > App.screen.height then break end
+    local next_loc2 = Text.next_screen_line(State, loc2)
+    if Text.eq2(next_loc2, loc2) then break end  -- end of file
+    loc2 = next_loc2
+  end
+end
+
+function Text.previous_screen_top1(State)
   -- duplicate some logic from love.draw
-  local top2 = Text.to2(State, State.screen_top1)
---?   print(App.screen.height)
+  -- does not modify State (except to populate line_cache)
+  local loc2 = Text.to2(State, State.screen_top1)
   local y = App.screen.height - State.line_height
   while y >= State.top do
---?     print(y, top2.line, top2.screen_line, top2.screen_pos)
-    if State.screen_top1.line == 1 and State.screen_top1.pos == 1 then break end
-    if State.lines[State.screen_top1.line].mode == 'text' then
+    if loc2.line == 1 and loc2.screen_line == 1 and loc2.screen_pos == 1 then break end
+    if State.lines[loc2.line].mode == 'text' then
       y = y - State.line_height
-    elseif State.lines[State.screen_top1.line].mode == 'drawing' then
-      y = y - Drawing_padding_height - Drawing.pixels(State.lines[State.screen_top1.line].h, State.width)
+    elseif State.lines[loc2.line].mode == 'drawing' then
+      y = y - Drawing_padding_height - Drawing.pixels(State.lines[loc2.line].h, State.width)
     end
-    top2 = Text.previous_screen_line(State, top2)
+    loc2 = Text.previous_screen_line(State, loc2)
   end
-  State.screen_top1 = Text.to1(State, top2)
-  State.cursor1 = {line=State.screen_top1.line, pos=State.screen_top1.pos}
-  Text.move_cursor_down_to_next_text_line_while_scrolling_again_if_necessary(State)
---?   print(State.cursor1.line, State.cursor1.pos, State.screen_top1.line, State.screen_top1.pos)
---?   print('pageup end')
+  return Text.to1(State, loc2)
 end
 
 function Text.pagedown(State)
---?   print('pagedown')
-  State.screen_top1 = {line=State.screen_bottom1.line, pos=State.screen_bottom1.pos}
---?   print('setting top to', State.screen_top1.line, State.screen_top1.pos)
+  State.screen_top1 = Text.screen_bottom1(State)
   State.cursor1 = {line=State.screen_top1.line, pos=State.screen_top1.pos}
   Text.move_cursor_down_to_next_text_line_while_scrolling_again_if_necessary(State)
---?   print('top now', State.screen_top1.line)
   Text.redraw_all(State)  -- if we're scrolling, reclaim all fragments to avoid memory leaks
---?   print('pagedown end')
+end
+
+-- return the location of the start of the bottom-most line on screen
+function Text.screen_bottom1(State)
+  -- duplicate some logic from love.draw
+  -- does not modify State (except to populate line_cache)
+  local loc2 = Text.to2(State, State.screen_top1)
+  local y = State.top
+  while true do
+    if State.lines[loc2.line].mode == 'text' then
+      y = y + State.line_height
+    elseif State.lines[loc2.line].mode == 'drawing' then
+      y = y + Drawing_padding_height + Drawing.pixels(State.lines[loc2.line].h, State.width)
+    end
+    if y + State.line_height > App.screen.height then break end
+    local next_loc2 = Text.next_screen_line(State, loc2)
+    if Text.eq2(next_loc2, loc2) then break end
+    loc2 = next_loc2
+  end
+  return Text.to1(State, loc2)
 end
 
 function Text.up(State)
@@ -505,7 +544,7 @@ end
 
 function Text.down(State)
   assert(State.lines[State.cursor1.line].mode == 'text', 'line is not text')
---?   print('down', State.cursor1.line, State.cursor1.pos, State.screen_top1.line, State.screen_top1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
+--?   print('down', State.cursor1.line, State.cursor1.pos, State.screen_top1.line, State.screen_top1.pos)
   assert(State.cursor1.pos, 'cursor has no pos')
   if Text.cursor_at_final_screen_line(State) then
     -- line is done, skip to next text line
@@ -522,7 +561,9 @@ function Text.down(State)
         break
       end
     end
-    if State.cursor1.line > State.screen_bottom1.line then
+    local screen_bottom1 = Text.screen_bottom1(State)
+--?   print('down 2', State.cursor1.line, State.cursor1.pos, State.screen_top1.line, State.screen_top1.pos, screen_bottom1.line, screen_bottom1.pos)
+    if State.cursor1.line > screen_bottom1.line then
 --?       print('screen top before:', State.screen_top1.line, State.screen_top1.pos)
 --?       print('scroll up preserving cursor')
       Text.snap_cursor_to_bottom_of_screen(State)
@@ -530,7 +571,8 @@ function Text.down(State)
     end
   else
     -- move down one screen line in current line
-    local scroll_down = Text.le1(State.screen_bottom1, State.cursor1)
+    local screen_bottom1 = Text.screen_bottom1(State)
+    local scroll_down = Text.le1(screen_bottom1, State.cursor1)
 --?     print('cursor is NOT at final screen line of its line')
     local screen_line_starting_pos, screen_line_index = Text.pos_at_start_of_screen_line(State, State.cursor1)
     Text.populate_screen_line_starting_pos(State, State.cursor1.line)
@@ -546,7 +588,7 @@ function Text.down(State)
 --?       print('screen top after:', State.screen_top1.line, State.screen_top1.pos)
     end
   end
---?   print('=>', State.cursor1.line, State.cursor1.pos, State.screen_top1.line, State.screen_top1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
+--?   print('=>', State.cursor1.line, State.cursor1.pos, State.screen_top1.line, State.screen_top1.pos)
 end
 
 function Text.start_of_line(State)
@@ -683,6 +725,7 @@ function Text.pos_at_start_of_screen_line(State, loc1)
 end
 
 function Text.pos_at_end_of_screen_line(State, loc1)
+  assert(State.lines[loc1.line].mode == 'text')
   Text.populate_screen_line_starting_pos(State, loc1.line)
   local line_cache = State.line_cache[loc1.line]
   local most_recent_final_pos = utf8.len(State.lines[loc1.line].data)+1
@@ -696,6 +739,25 @@ function Text.pos_at_end_of_screen_line(State, loc1)
   assert(false, ('invalid pos %d'):format(loc1.pos))
 end
 
+function Text.final_text_loc_on_screen(State)
+  local screen_bottom1 = Text.screen_bottom1(State)
+  if State.lines[screen_bottom1.line].mode == 'text' then
+    return {
+      line=screen_bottom1.line,
+      pos=Text.pos_at_end_of_screen_line(State, screen_bottom1),
+    }
+  end
+  local loc2 = Text.to2(State, screen_bottom1)
+  while true do
+    if State.lines[loc2.line].mode == 'text' then break end
+    assert(loc2.line > 1 or loc2.screen_line > 1 and loc2.screen_pos > 1)  -- elsewhere we're making sure there's always at least one text line on screen
+    loc2 = Text.previous_screen_line(State, loc2)
+  end
+  local result = Text.to1(State, loc2)
+  result.pos = Text.pos_at_end_of_screen_line(State, result)
+  return result
+end
+
 function Text.cursor_at_final_screen_line(State)
   Text.populate_screen_line_starting_pos(State, State.cursor1.line)
   local screen_lines = State.line_cache[State.cursor1.line].screen_line_starting_pos
@@ -736,7 +798,7 @@ function Text.snap_cursor_to_bottom_of_screen(State)
 --?   print('to2: =>', top2.line, top2.screen_line, top2.screen_pos)
   -- slide to start of screen line
   top2.screen_pos = 1  -- start of screen line
---?   print('snap', State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
+--?   print('snap', State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos)
 --?   print('cursor pos '..tostring(State.cursor1.pos)..' is on the #'..tostring(top2.screen_line)..' screen line down')
   local y = App.screen.height - State.line_height
   -- duplicate some logic from love.draw
@@ -766,26 +828,28 @@ function Text.snap_cursor_to_bottom_of_screen(State)
 --?   print('top2 finally:', top2.line, top2.screen_line, top2.screen_pos)
   State.screen_top1 = Text.to1(State, top2)
 --?   print('top1 finally:', State.screen_top1.line, State.screen_top1.pos)
---?   print('snap =>', State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
+--?   print('snap =>', State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos)
   Text.redraw_all(State)  -- if we're scrolling, reclaim all fragments to avoid memory leaks
 end
 
 function Text.in_line(State, line_index, x,y)
   local line = State.lines[line_index]
   local line_cache = State.line_cache[line_index]
-  if line_cache.starty == nil then return false end  -- outside current page
-  if y < line_cache.starty then return false end
+  local starty = Text.starty(State, line_index)
+  if starty == nil then return false end  -- outside current page
+  if y < starty then return false end
   Text.populate_screen_line_starting_pos(State, line_index)
-  return y < line_cache.starty + State.line_height*(#line_cache.screen_line_starting_pos - Text.screen_line_index(line_cache.screen_line_starting_pos, line_cache.startpos) + 1)
+  return y < starty + State.line_height*(#line_cache.screen_line_starting_pos - Text.screen_line_index(line_cache.screen_line_starting_pos, line_cache.startpos) + 1)
 end
 
 -- convert mx,my in pixels to schema-1 coordinates
 function Text.to_pos_on_line(State, line_index, mx, my)
   local line = State.lines[line_index]
   local line_cache = State.line_cache[line_index]
-  assert(my >= line_cache.starty, 'failed to map y pixel to line')
+  local starty = Text.starty(State, line_index)
+  assert(my >= starty, 'failed to map y pixel to line')
   -- duplicate some logic from Text.draw
-  local y = line_cache.starty
+  local y = starty
   local start_screen_line_index = Text.screen_line_index(line_cache.screen_line_starting_pos, line_cache.startpos)
   for screen_line_index = start_screen_line_index,#line_cache.screen_line_starting_pos do
     local screen_line_starting_pos = line_cache.screen_line_starting_pos[screen_line_index]
@@ -971,6 +1035,10 @@ function Text.le1(a, b)
   return a.pos <= b.pos
 end
 
+function Text.eq2(a, b)
+  return a.line == b.line and a.screen_line == b.screen_line and a.screen_pos == b.screen_pos
+end
+
 function Text.offset(s, pos1)
   if pos1 == 1 then return 1 end
   local result = utf8.offset(s, pos1)
@@ -994,6 +1062,22 @@ function Text.previous_screen_line(State, loc2)
   end
 end
 
+function Text.next_screen_line(State, loc2)
+  if State.lines[loc2.line].mode == 'drawing' then
+    return {line=loc2.line+1, screen_line=1, screen_pos=1}
+  end
+  Text.populate_screen_line_starting_pos(State, loc2.line)
+  if loc2.screen_line >= #State.line_cache[loc2.line].screen_line_starting_pos then
+    if loc2.line < #State.lines then
+      return {line=loc2.line+1, screen_line=1, screen_pos=1}
+    else
+      return loc2
+    end
+  else
+    return {line=loc2.line, screen_line=loc2.screen_line+1, screen_pos=1}
+  end
+end
+
 -- resize helper
 function Text.tweak_screen_top_and_cursor(State)
   if State.screen_top1.pos == 1 then return end
@@ -1017,16 +1101,12 @@ function Text.tweak_screen_top_and_cursor(State)
     end
   end
   -- make sure cursor is on screen
+  local screen_bottom1 = Text.screen_bottom1(State)
   if Text.lt1(State.cursor1, State.screen_top1) then
     State.cursor1 = {line=State.screen_top1.line, pos=State.screen_top1.pos}
-  elseif State.cursor1.line >= State.screen_bottom1.line then
---?     print('too low')
+  elseif State.cursor1.line >= screen_bottom1.line then
     if Text.cursor_out_of_screen(State) then
---?       print('tweak')
-      State.cursor1 = {
-          line=State.screen_bottom1.line,
-          pos=Text.to_pos_on_line(State, State.screen_bottom1.line, State.right-5, App.screen.height-5),
-      }
+      State.cursor1 = Text.final_text_loc_on_screen(State)
     end
   end
 end
@@ -1035,11 +1115,6 @@ end
 function Text.cursor_out_of_screen(State)
   edit.draw(State)
   return State.cursor_y == nil
-  -- this approach is cheaper and almost works, except on the final screen
-  -- where file ends above bottom of screen
---?   local botpos = Text.pos_at_start_of_screen_line(State, State.cursor1)
---?   local botline1 = {line=State.cursor1.line, pos=botpos}
---?   return Text.lt1(State.screen_bottom1, botline1)
 end
 
 function Text.redraw_all(State)
diff --git a/source_text_tests.lua b/source_text_tests.lua
index 6376ec8..11cc823 100644
--- a/source_text_tests.lua
+++ b/source_text_tests.lua
@@ -16,7 +16,7 @@ function test_initial_state()
 end
 
 function test_click_to_create_drawing()
-  App.screen.init{width=120, height=60}
+  App.screen.init{width=800, height=600}
   Editor_state = edit.initialize_test_state()
   Editor_state.lines = load_array{}
   Text.redraw_all(Editor_state)
@@ -75,7 +75,6 @@ function test_press_ctrl()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.run_after_keychord(Editor_state, 'C-m', 'm')
 end
 
@@ -232,7 +231,7 @@ function test_skip_multiple_spaces_to_next_word()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=4}  -- at the start of second word
   edit.draw(Editor_state)
-  edit.run_after_keychord(Editor_state, 'M-right',  'right')
+  edit.run_after_keychord(Editor_state, 'M-right', 'right')
   check_eq(Editor_state.cursor1.pos, 9, 'check')
 end
 
@@ -243,7 +242,7 @@ function test_move_past_end_of_word_on_next_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=8}
   edit.draw(Editor_state)
-  edit.run_after_keychord(Editor_state, 'M-right',  'right')
+  edit.run_after_keychord(Editor_state, 'M-right', 'right')
   check_eq(Editor_state.cursor1.line, 2, 'line')
   check_eq(Editor_state.cursor1.pos, 4, 'pos')
 end
@@ -255,9 +254,8 @@ function test_click_moves_cursor()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
-  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
+  edit.draw(Editor_state)  -- populate line_cache.startpos for each line
   edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
   check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
   check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
@@ -274,7 +272,6 @@ function test_click_to_left_of_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=3}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
   -- click to the left of the line
   edit.draw(Editor_state)
@@ -294,7 +291,6 @@ function test_click_takes_margins_into_account()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
   -- click on the other line
   edit.draw(Editor_state)
@@ -313,7 +309,6 @@ function test_click_on_empty_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
   -- click on the empty line
   edit.draw(Editor_state)
@@ -332,7 +327,6 @@ function test_click_below_all_lines()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
   -- click below first line
   edit.draw(Editor_state)
@@ -350,7 +344,6 @@ function test_draw_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'screen:1')
@@ -367,7 +360,6 @@ function test_draw_wrapping_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'screen:1')
@@ -384,7 +376,6 @@ function test_draw_word_wrapping_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc ', 'screen:1')
@@ -402,7 +393,6 @@ function test_click_on_wrapping_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=20}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- click on the other line
   edit.draw(Editor_state)
   edit.run_after_mouse_click(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
@@ -421,7 +411,6 @@ function test_click_on_wrapping_line_takes_margins_into_account()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=20}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- click on the other line
   edit.draw(Editor_state)
   edit.run_after_mouse_click(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
@@ -439,7 +428,6 @@ function test_draw_text_wrapping_within_word()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abcd ', 'screen:1')
@@ -457,7 +445,6 @@ function test_draw_wrapping_text_containing_non_ascii()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'mad', 'screen:1')
@@ -476,7 +463,6 @@ function test_click_past_end_of_screen_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'madam ', 'baseline/screen:1')
@@ -499,7 +485,6 @@ function test_click_on_wrapping_line_rendered_from_partway_at_top_of_screen()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=8}
   Editor_state.screen_top1 = {line=1, pos=7}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, "I'm ad", 'baseline/screen:2')
@@ -520,7 +505,6 @@ function test_click_past_end_of_wrapping_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'madam ', 'baseline/screen:1')
@@ -544,7 +528,6 @@ function test_click_past_end_of_wrapping_line_containing_non_ascii()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'madam ', 'baseline/screen:1')
@@ -569,7 +552,6 @@ function test_click_past_end_of_word_wrapping_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'the quick brown fox ', 'baseline/screen:1')
@@ -588,11 +570,10 @@ function test_select_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- select a letter
   App.fake_key_press('lshift')
-  edit.run_after_keychord(Editor_state, 'S-right',  'right')
+  edit.run_after_keychord(Editor_state, 'S-right', 'right')
   App.fake_key_release('lshift')
   edit.key_release(Editor_state, 'lshift')
   -- selection persists even after shift is released
@@ -611,10 +592,9 @@ function test_cursor_movement_without_shift_resets_selection()
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.selection1 = {line=1, pos=2}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- press an arrow key without shift
-  edit.run_after_keychord(Editor_state, 'right',  'right')
+  edit.run_after_keychord(Editor_state, 'right', 'right')
   -- no change to data, selection is reset
   check_nil(Editor_state.selection1.line, 'check')
   check_eq(Editor_state.lines[1].data, 'abc', 'data')
@@ -629,7 +609,6 @@ function test_edit_deletes_selection()
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.selection1 = {line=1, pos=2}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- press a key
   edit.run_after_text_input(Editor_state, 'x')
@@ -646,7 +625,6 @@ function test_edit_with_shift_key_deletes_selection()
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.selection1 = {line=1, pos=2}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- mimic precise keypresses for a capital letter
   App.fake_key_press('lshift')
@@ -668,7 +646,6 @@ function test_copy_does_not_reset_selection()
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.selection1 = {line=1, pos=2}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- copy selection
   edit.run_after_keychord(Editor_state, 'C-c', 'c')
@@ -686,7 +663,6 @@ function test_cut()
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.selection1 = {line=1, pos=2}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- press a key
   edit.run_after_keychord(Editor_state, 'C-x', 'x')
@@ -704,7 +680,6 @@ function test_paste_replaces_selection()
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.selection1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- set clipboard
   App.clipboard = 'xyz'
@@ -723,7 +698,6 @@ function test_deleting_selection_may_scroll()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=2}
   Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'def', 'baseline/screen:1')
@@ -747,7 +721,6 @@ function test_edit_wrapping_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=4}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   edit.run_after_text_input(Editor_state, 'g')
   local y = Editor_state.top
@@ -766,7 +739,6 @@ function test_insert_newline()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=2}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -795,7 +767,6 @@ function test_insert_newline_at_start_of_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- hitting the enter key splits the line
   edit.run_after_keychord(Editor_state, 'return', 'return')
   check_eq(Editor_state.cursor1.line, 2, 'cursor:line')
@@ -812,7 +783,6 @@ function test_insert_from_clipboard()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=2}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -841,9 +811,8 @@ function test_select_text_using_mouse()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
-  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
+  edit.draw(Editor_state)  -- populate line_cache.startpos for each line
   -- press and hold on first location
   edit.run_after_mouse_press(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
   -- drag and release somewhere else
@@ -861,9 +830,8 @@ function test_select_text_using_mouse_starting_above_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
-  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
+  edit.draw(Editor_state)  -- populate line_cache.startpos for each line
   -- press mouse above first line of text
   edit.run_after_mouse_press(Editor_state, Editor_state.left+8,5, 1)
   check(Editor_state.selection1.line ~= nil, 'selection:line-not-nil')
@@ -879,7 +847,6 @@ function test_select_text_using_mouse_starting_above_text_wrapping_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=5}
   Editor_state.screen_top1 = {line=2, pos=3}
-  Editor_state.screen_bottom1 = {}
   -- press mouse above first line of text
   edit.draw(Editor_state)
   edit.run_after_mouse_press(Editor_state, Editor_state.left+8,5, 1)
@@ -902,7 +869,6 @@ function test_select_text_using_mouse_starting_below_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'ab', 'baseline:screen:1')
@@ -923,9 +889,8 @@ function test_select_text_using_mouse_and_shift()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
-  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
+  edit.draw(Editor_state)  -- populate line_cache.startpos for each line
   -- click on first location
   edit.run_after_mouse_press(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
   edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
@@ -948,9 +913,8 @@ function test_select_text_repeatedly_using_mouse_and_shift()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
-  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
+  edit.draw(Editor_state)  -- populate line_cache.startpos for each line
   -- click on first location
   edit.run_after_mouse_press(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
   edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
@@ -978,7 +942,6 @@ function test_select_all_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- select all
   App.fake_key_press('lctrl')
@@ -1000,7 +963,6 @@ function test_cut_without_selection()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=2}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
   edit.draw(Editor_state)
   -- try to cut without selecting text
@@ -1016,7 +978,6 @@ function test_pagedown()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- initially the first two lines are displayed
   edit.draw(Editor_state)
   local y = Editor_state.top
@@ -1046,7 +1007,6 @@ function test_pagedown_skips_drawings()
   check_eq(Editor_state.lines[2].mode, 'drawing', 'baseline/lines')
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   local drawing_height = Drawing_padding_height + drawing_width/2  -- default
   -- initially the screen displays the first line and the drawing
   -- 15px margin + 15px line1 + 10px margin + 25px drawing + 10px margin = 75px < screen height 80px
@@ -1070,7 +1030,6 @@ function test_pagedown_can_start_from_middle_of_long_wrapping_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=2}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc ', 'baseline/screen:1')
@@ -1105,7 +1064,6 @@ function test_pagedown_never_moves_up()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=9}
   Editor_state.screen_top1 = {line=1, pos=9}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- pagedown makes no change
   edit.run_after_keychord(Editor_state, 'pagedown', 'pagedown')
@@ -1120,7 +1078,6 @@ function test_down_arrow_moves_cursor()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- initially the first three lines are displayed
   edit.draw(Editor_state)
   local y = Editor_state.top
@@ -1153,7 +1110,6 @@ function test_down_arrow_skips_drawing()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -1175,7 +1131,6 @@ function test_down_arrow_scrolls_down_by_one_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -1203,7 +1158,6 @@ function test_down_arrow_scrolls_down_by_one_screen_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -1232,7 +1186,6 @@ function test_down_arrow_scrolls_down_by_one_screen_line_after_splitting_within_
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -1260,7 +1213,6 @@ function test_pagedown_followed_by_down_arrow_does_not_scroll_screen_up()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -1294,7 +1246,6 @@ function test_up_arrow_moves_cursor()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -1326,7 +1277,6 @@ function test_up_arrow_skips_drawing()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -1348,7 +1298,6 @@ function test_up_arrow_scrolls_up_by_one_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'def', 'baseline/screen:1')
@@ -1376,7 +1325,6 @@ function test_up_arrow_scrolls_up_by_one_line_skipping_drawing()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=1}
   Editor_state.screen_top1 = {line=3, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'def', 'baseline/screen:1')
@@ -1398,7 +1346,6 @@ function test_up_arrow_scrolls_up_by_one_screen_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=6}
   Editor_state.screen_top1 = {line=3, pos=5}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'jkl', 'baseline/screen:1')
@@ -1426,7 +1373,6 @@ function test_up_arrow_scrolls_up_to_final_screen_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'ghi', 'baseline/screen:1')
@@ -1456,7 +1402,6 @@ function test_up_arrow_scrolls_up_to_empty_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -1483,7 +1428,6 @@ function test_pageup()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- initially the last two lines are displayed
   edit.draw(Editor_state)
   local y = Editor_state.top
@@ -1508,7 +1452,6 @@ function test_pageup_scrolls_up_by_screen_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'ghi', 'baseline/screen:1')
@@ -1537,7 +1480,6 @@ function test_pageup_scrolls_up_from_middle_screen_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=5}
   Editor_state.screen_top1 = {line=2, pos=5}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'jkl', 'baseline/screen:2')
@@ -1564,7 +1506,6 @@ function test_enter_on_bottom_line_scrolls_down()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=2}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -1593,7 +1534,6 @@ function test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=4, pos=2}
   Editor_state.screen_top1 = {line=4, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'jkl', 'baseline/screen:1')
@@ -1616,7 +1556,6 @@ function test_inserting_text_on_final_line_avoids_scrolling_down_when_not_at_bot
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- after hitting the inserting_text key the screen does not scroll down
   edit.run_after_text_input(Editor_state, 'a')
@@ -1635,7 +1574,6 @@ function test_typing_on_bottom_line_scrolls_down()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=4}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -1665,7 +1603,6 @@ function test_left_arrow_scrolls_up_in_wrapped_line()
   Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
   Text.redraw_all(Editor_state)
   Editor_state.screen_top1 = {line=3, pos=5}
-  Editor_state.screen_bottom1 = {}
   -- cursor is at top of screen
   Editor_state.cursor1 = {line=3, pos=5}
   edit.draw(Editor_state)
@@ -1694,7 +1631,6 @@ function test_right_arrow_scrolls_down_in_wrapped_line()
   Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
   Text.redraw_all(Editor_state)
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- cursor is at bottom right of screen
   Editor_state.cursor1 = {line=3, pos=5}
   edit.draw(Editor_state)
@@ -1705,7 +1641,7 @@ function test_right_arrow_scrolls_down_in_wrapped_line()
   y = y + Editor_state.line_height
   App.screen.check(y, 'ghi ', 'baseline/screen:3')  -- line wrapping includes trailing whitespace
   -- after hitting the right arrow the screen scrolls down by one line
-  edit.run_after_keychord(Editor_state, 'right',  'right')
+  edit.run_after_keychord(Editor_state, 'right', 'right')
   check_eq(Editor_state.screen_top1.line, 2, 'screen_top')
   check_eq(Editor_state.cursor1.line, 3, 'cursor:line')
   check_eq(Editor_state.cursor1.pos, 6, 'cursor:pos')
@@ -1724,7 +1660,6 @@ function test_home_scrolls_up_in_wrapped_line()
   Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
   Text.redraw_all(Editor_state)
   Editor_state.screen_top1 = {line=3, pos=5}
-  Editor_state.screen_bottom1 = {}
   -- cursor is at top of screen
   Editor_state.cursor1 = {line=3, pos=5}
   edit.draw(Editor_state)
@@ -1753,7 +1688,6 @@ function test_end_scrolls_down_in_wrapped_line()
   Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
   Text.redraw_all(Editor_state)
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- cursor is at bottom right of screen
   Editor_state.cursor1 = {line=3, pos=5}
   edit.draw(Editor_state)
@@ -1784,7 +1718,6 @@ function test_position_cursor_on_recently_edited_wrapping_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=25}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc def ghi ', 'baseline1/screen:1')
@@ -1818,7 +1751,6 @@ function test_backspace_can_scroll_up()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'def', 'baseline/screen:1')
@@ -1846,7 +1778,6 @@ function test_backspace_can_scroll_up_screen_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=5}
   Editor_state.screen_top1 = {line=3, pos=5}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'jkl', 'baseline/screen:1')
@@ -1981,7 +1912,6 @@ function test_undo_insert_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=4}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- insert a character
   edit.draw(Editor_state)
   edit.run_after_text_input(Editor_state, 'g')
@@ -2016,7 +1946,6 @@ function test_undo_delete_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=5}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- delete a character
   edit.run_after_keychord(Editor_state, 'backspace', 'backspace')
   check_eq(Editor_state.cursor1.line, 2, 'baseline/cursor:line')
@@ -2055,7 +1984,6 @@ function test_undo_restores_selection()
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.selection1 = {line=1, pos=2}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- delete selected text
   edit.run_after_text_input(Editor_state, 'x')
@@ -2076,7 +2004,6 @@ function test_search()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- search for a string
   edit.run_after_keychord(Editor_state, 'C-f', 'f')
@@ -2103,7 +2030,6 @@ function test_search_upwards()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- search for a string
   edit.run_after_keychord(Editor_state, 'C-f', 'f')
@@ -2121,7 +2047,6 @@ function test_search_wrap()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- search for a string
   edit.run_after_keychord(Editor_state, 'C-f', 'f')
@@ -2139,7 +2064,6 @@ function test_search_wrap_upwards()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- search upwards for a string
   edit.run_after_keychord(Editor_state, 'C-f', 'f')
diff --git a/text.lua b/text.lua
index ad86378..ec28509 100644
--- a/text.lua
+++ b/text.lua
@@ -2,15 +2,13 @@
 Text = {}
 
 -- draw a line starting from startpos to screen at y between State.left and State.right
--- return y for the next line, and position of start of final screen line drawn
+-- return y for the next line
 function Text.draw(State, line_index, y, startpos)
 --?   print('text.draw', line_index, y)
   local line = State.lines[line_index]
   local line_cache = State.line_cache[line_index]
-  line_cache.starty = y
   line_cache.startpos = startpos
   -- wrap long lines
-  local final_screen_line_starting_pos = startpos  -- track value to return
   Text.populate_screen_line_starting_pos(State, line_index)
   assert(#line_cache.screen_line_starting_pos >= 1, 'line cache missing screen line info')
   for i=1,#line_cache.screen_line_starting_pos do
@@ -18,7 +16,6 @@ function Text.draw(State, line_index, y, startpos)
     if pos < startpos then
       -- render nothing
     else
-      final_screen_line_starting_pos = pos
       local screen_line = Text.screen_line(line, line_cache, i)
 --?       print('text.draw:', screen_line, 'at', line_index,pos, 'after', x,y)
       local frag_len = utf8.len(screen_line)
@@ -57,7 +54,7 @@ function Text.draw(State, line_index, y, startpos)
       end
     end
   end
-  return y, final_screen_line_starting_pos
+  return y
 end
 
 function Text.screen_line(line, line_cache, i)
@@ -226,45 +223,64 @@ function Text.keychord_press(State, chord)
 end
 
 function Text.pageup(State)
---?   print('pageup')
+  State.screen_top1 = Text.previous_screen_top1(State)
+  State.cursor1 = {line=State.screen_top1.line, pos=State.screen_top1.pos}
+  Text.move_cursor_down_to_next_text_line_while_scrolling_again_if_necessary(State)
+  Text.redraw_all(State)  -- if we're scrolling, reclaim all fragments to avoid memory leaks
+end
+
+-- return the top y coordinate of a given line_index,
+-- or nil if no part of it is on screen
+function Text.starty(State, line_index)
+  -- duplicate some logic from love.draw
+  -- does not modify State (except to populate line_cache)
+  if line_index < State.screen_top1.line then return end
+  local loc2 = Text.to2(State, State.screen_top1)
+  local y = State.top
+  while true do
+    if loc2.line == line_index then return y end
+    y = y + State.line_height
+    if y + State.line_height > App.screen.height then break end
+    local next_loc2 = Text.next_screen_line(State, loc2)
+    if Text.eq2(next_loc2, loc2) then break end  -- end of file
+    loc2 = next_loc2
+  end
+end
+
+function Text.previous_screen_top1(State)
   -- duplicate some logic from love.draw
-  local top2 = Text.to2(State, State.screen_top1)
---?   print(App.screen.height)
+  -- does not modify State (except to populate line_cache)
+  local loc2 = Text.to2(State, State.screen_top1)
   local y = App.screen.height - State.line_height
   while y >= State.top do
---?     print(y, top2.line, top2.screen_line, top2.screen_pos)
-    if State.screen_top1.line == 1 and State.screen_top1.pos == 1 then break end
+    if loc2.line == 1 and loc2.screen_line == 1 and loc2.screen_pos == 1 then break end
     y = y - State.line_height
-    top2 = Text.previous_screen_line(State, top2)
+    loc2 = Text.previous_screen_line(State, loc2)
   end
-  State.screen_top1 = Text.to1(State, top2)
-  State.cursor1 = {line=State.screen_top1.line, pos=State.screen_top1.pos}
-  Text.move_cursor_down_to_next_text_line_while_scrolling_again_if_necessary(State)
---?   print(State.cursor1.line, State.cursor1.pos, State.screen_top1.line, State.screen_top1.pos)
---?   print('pageup end')
+  return Text.to1(State, loc2)
 end
 
 function Text.pagedown(State)
---?   print('pagedown')
-  -- If a line/paragraph gets to a page boundary, I often want to scroll
-  -- before I get to the bottom.
-  -- However, only do this if it makes forward progress.
-  local bot2 = Text.to2(State, State.screen_bottom1)
-  if bot2.screen_line > 1 then
-    bot2.screen_line = math.max(bot2.screen_line-10, 1)
-  end
-  local new_top1 = Text.to1(State, bot2)
-  if Text.lt1(State.screen_top1, new_top1) then
-    State.screen_top1 = new_top1
-  else
-    State.screen_top1 = {line=State.screen_bottom1.line, pos=State.screen_bottom1.pos}
-  end
---?   print('setting top to', State.screen_top1.line, State.screen_top1.pos)
+  State.screen_top1 = Text.screen_bottom1(State)
   State.cursor1 = {line=State.screen_top1.line, pos=State.screen_top1.pos}
   Text.move_cursor_down_to_next_text_line_while_scrolling_again_if_necessary(State)
---?   print('top now', State.screen_top1.line)
   Text.redraw_all(State)  -- if we're scrolling, reclaim all fragments to avoid memory leaks
---?   print('pagedown end')
+end
+
+-- return the location of the start of the bottom-most line on screen
+function Text.screen_bottom1(State)
+  -- duplicate some logic from love.draw
+  -- does not modify State (except to populate line_cache)
+  local loc2 = Text.to2(State, State.screen_top1)
+  local y = State.top
+  while true do
+    y = y + State.line_height
+    if y + State.line_height > App.screen.height then break end
+    local next_loc2 = Text.next_screen_line(State, loc2)
+    if Text.eq2(next_loc2, loc2) then break end
+    loc2 = next_loc2
+  end
+  return Text.to1(State, loc2)
 end
 
 function Text.up(State)
@@ -306,7 +322,7 @@ function Text.up(State)
 end
 
 function Text.down(State)
---?   print('down', State.cursor1.line, State.cursor1.pos, State.screen_top1.line, State.screen_top1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
+--?   print('down', State.cursor1.line, State.cursor1.pos, State.screen_top1.line, State.screen_top1.pos)
   assert(State.cursor1.pos, 'cursor has no pos')
   if Text.cursor_at_final_screen_line(State) then
     -- line is done, skip to next text line
@@ -317,7 +333,9 @@ function Text.down(State)
       State.cursor1.pos = Text.nearest_cursor_pos(State.font, State.lines[State.cursor1.line].data, State.cursor_x, State.left)
 --?       print(State.cursor1.pos)
     end
-    if State.cursor1.line > State.screen_bottom1.line then
+    local screen_bottom1 = Text.screen_bottom1(State)
+--?   print('down 2', State.cursor1.line, State.cursor1.pos, State.screen_top1.line, State.screen_top1.pos, screen_bottom1.line, screen_bottom1.pos)
+    if State.cursor1.line > screen_bottom1.line then
 --?       print('screen top before:', State.screen_top1.line, State.screen_top1.pos)
 --?       print('scroll up preserving cursor')
       Text.snap_cursor_to_bottom_of_screen(State)
@@ -325,7 +343,8 @@ function Text.down(State)
     end
   else
     -- move down one screen line in current line
-    local scroll_down = Text.le1(State.screen_bottom1, State.cursor1)
+    local screen_bottom1 = Text.screen_bottom1(State)
+    local scroll_down = Text.le1(screen_bottom1, State.cursor1)
 --?     print('cursor is NOT at final screen line of its line')
     local screen_line_starting_pos, screen_line_index = Text.pos_at_start_of_screen_line(State, State.cursor1)
     Text.populate_screen_line_starting_pos(State, State.cursor1.line)
@@ -341,7 +360,7 @@ function Text.down(State)
 --?       print('screen top after:', State.screen_top1.line, State.screen_top1.pos)
     end
   end
---?   print('=>', State.cursor1.line, State.cursor1.pos, State.screen_top1.line, State.screen_top1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
+--?   print('=>', State.cursor1.line, State.cursor1.pos, State.screen_top1.line, State.screen_top1.pos)
 end
 
 function Text.start_of_line(State)
@@ -474,6 +493,14 @@ function Text.pos_at_end_of_screen_line(State, loc1)
   assert(false, ('invalid pos %d'):format(loc1.pos))
 end
 
+function Text.final_text_loc_on_screen(State)
+  local screen_bottom1 = Text.screen_bottom1(State)
+  return {
+    line=screen_bottom1.line,
+    pos=Text.pos_at_end_of_screen_line(State, screen_bottom1),
+  }
+end
+
 function Text.cursor_at_final_screen_line(State)
   Text.populate_screen_line_starting_pos(State, State.cursor1.line)
   local screen_lines = State.line_cache[State.cursor1.line].screen_line_starting_pos
@@ -495,7 +522,7 @@ function Text.snap_cursor_to_bottom_of_screen(State)
 --?   print('to2: =>', top2.line, top2.screen_line, top2.screen_pos)
   -- slide to start of screen line
   top2.screen_pos = 1  -- start of screen line
---?   print('snap', State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
+--?   print('snap', State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos)
 --?   print('cursor pos '..tostring(State.cursor1.pos)..' is on the #'..tostring(top2.screen_line)..' screen line down')
   local y = App.screen.height - State.line_height
   -- duplicate some logic from love.draw
@@ -512,26 +539,28 @@ function Text.snap_cursor_to_bottom_of_screen(State)
 --?   print('top2 finally:', top2.line, top2.screen_line, top2.screen_pos)
   State.screen_top1 = Text.to1(State, top2)
 --?   print('top1 finally:', State.screen_top1.line, State.screen_top1.pos)
---?   print('snap =>', State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
+--?   print('snap =>', State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos)
   Text.redraw_all(State)  -- if we're scrolling, reclaim all fragments to avoid memory leaks
 end
 
 function Text.in_line(State, line_index, x,y)
   local line = State.lines[line_index]
   local line_cache = State.line_cache[line_index]
-  if line_cache.starty == nil then return false end  -- outside current page
-  if y < line_cache.starty then return false end
+  local starty = Text.starty(State, line_index)
+  if starty == nil then return false end  -- outside current page
+  if y < starty then return false end
   Text.populate_screen_line_starting_pos(State, line_index)
-  return y < line_cache.starty + State.line_height*(#line_cache.screen_line_starting_pos - Text.screen_line_index(line_cache.screen_line_starting_pos, line_cache.startpos) + 1)
+  return y < starty + State.line_height*(#line_cache.screen_line_starting_pos - Text.screen_line_index(line_cache.screen_line_starting_pos, line_cache.startpos) + 1)
 end
 
 -- convert mx,my in pixels to schema-1 coordinates
 function Text.to_pos_on_line(State, line_index, mx, my)
   local line = State.lines[line_index]
   local line_cache = State.line_cache[line_index]
-  assert(my >= line_cache.starty, 'failed to map y pixel to line')
+  local starty = Text.starty(State, line_index)
+  assert(my >= starty, 'failed to map y pixel to line')
   -- duplicate some logic from Text.draw
-  local y = line_cache.starty
+  local y = starty
   local start_screen_line_index = Text.screen_line_index(line_cache.screen_line_starting_pos, line_cache.startpos)
   for screen_line_index = start_screen_line_index,#line_cache.screen_line_starting_pos do
     local screen_line_starting_pos = line_cache.screen_line_starting_pos[screen_line_index]
@@ -714,6 +743,10 @@ function Text.le1(a, b)
   return a.pos <= b.pos
 end
 
+function Text.eq2(a, b)
+  return a.line == b.line and a.screen_line == b.screen_line and a.screen_pos == b.screen_pos
+end
+
 function Text.offset(s, pos1)
   if pos1 == 1 then return 1 end
   local result = utf8.offset(s, pos1)
@@ -735,6 +768,19 @@ function Text.previous_screen_line(State, loc2)
   end
 end
 
+function Text.next_screen_line(State, loc2)
+  Text.populate_screen_line_starting_pos(State, loc2.line)
+  if loc2.screen_line >= #State.line_cache[loc2.line].screen_line_starting_pos then
+    if loc2.line < #State.lines then
+      return {line=loc2.line+1, screen_line=1, screen_pos=1}
+    else
+      return loc2
+    end
+  else
+    return {line=loc2.line, screen_line=loc2.screen_line+1, screen_pos=1}
+  end
+end
+
 -- resize helper
 function Text.tweak_screen_top_and_cursor(State)
   if State.screen_top1.pos == 1 then return end
@@ -758,16 +804,12 @@ function Text.tweak_screen_top_and_cursor(State)
     end
   end
   -- make sure cursor is on screen
+  local screen_bottom1 = Text.screen_bottom1(State)
   if Text.lt1(State.cursor1, State.screen_top1) then
     State.cursor1 = {line=State.screen_top1.line, pos=State.screen_top1.pos}
-  elseif State.cursor1.line >= State.screen_bottom1.line then
---?     print('too low')
+  elseif State.cursor1.line >= screen_bottom1.line then
     if Text.cursor_out_of_screen(State) then
---?       print('tweak')
-      State.cursor1 = {
-          line=State.screen_bottom1.line,
-          pos=Text.to_pos_on_line(State, State.screen_bottom1.line, State.right-5, App.screen.height-5),
-      }
+      State.cursor1 = Text.final_text_loc_on_screen(State)
     end
   end
 end
@@ -776,11 +818,6 @@ end
 function Text.cursor_out_of_screen(State)
   edit.draw(State)
   return State.cursor_y == nil
-  -- this approach is cheaper and almost works, except on the final screen
-  -- where file ends above bottom of screen
---?   local botpos = Text.pos_at_start_of_screen_line(State, State.cursor1)
---?   local botline1 = {line=State.cursor1.line, pos=botpos}
---?   return Text.lt1(State.screen_bottom1, botline1)
 end
 
 function Text.redraw_all(State)
diff --git a/text_tests.lua b/text_tests.lua
index 541a056..ca97e7f 100644
--- a/text_tests.lua
+++ b/text_tests.lua
@@ -191,9 +191,8 @@ function test_click_moves_cursor()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
-  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
+  edit.draw(Editor_state)  -- populate line_cache.startpos for each line
   edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
   check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
   check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
@@ -210,7 +209,6 @@ function test_click_to_left_of_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=3}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
   -- click to the left of the line
   edit.draw(Editor_state)
@@ -230,7 +228,6 @@ function test_click_takes_margins_into_account()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
   -- click on the other line
   edit.draw(Editor_state)
@@ -249,7 +246,6 @@ function test_click_on_empty_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
   -- click on the empty line
   edit.draw(Editor_state)
@@ -268,7 +264,6 @@ function test_click_below_all_lines()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
   -- click below first line
   edit.draw(Editor_state)
@@ -286,7 +281,6 @@ function test_draw_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'screen:1')
@@ -303,7 +297,6 @@ function test_draw_wrapping_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'screen:1')
@@ -320,7 +313,6 @@ function test_draw_word_wrapping_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc ', 'screen:1')
@@ -338,7 +330,6 @@ function test_click_on_wrapping_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=20}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- click on the other line
   edit.draw(Editor_state)
   edit.run_after_mouse_click(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
@@ -357,7 +348,6 @@ function test_click_on_wrapping_line_takes_margins_into_account()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=20}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- click on the other line
   edit.draw(Editor_state)
   edit.run_after_mouse_click(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
@@ -375,7 +365,6 @@ function test_draw_text_wrapping_within_word()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abcd ', 'screen:1')
@@ -393,7 +382,6 @@ function test_draw_wrapping_text_containing_non_ascii()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'mad', 'screen:1')
@@ -412,7 +400,6 @@ function test_click_past_end_of_screen_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'madam ', 'baseline/screen:1')
@@ -435,7 +422,6 @@ function test_click_on_wrapping_line_rendered_from_partway_at_top_of_screen()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=8}
   Editor_state.screen_top1 = {line=1, pos=7}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, "I'm ad", 'baseline/screen:2')
@@ -456,7 +442,6 @@ function test_click_past_end_of_wrapping_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'madam ', 'baseline/screen:1')
@@ -480,7 +465,6 @@ function test_click_past_end_of_wrapping_line_containing_non_ascii()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'madam ', 'baseline/screen:1')
@@ -505,7 +489,6 @@ function test_click_past_end_of_word_wrapping_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'the quick brown fox ', 'baseline/screen:1')
@@ -524,7 +507,6 @@ function test_select_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- select a letter
   App.fake_key_press('lshift')
@@ -547,7 +529,6 @@ function test_cursor_movement_without_shift_resets_selection()
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.selection1 = {line=1, pos=2}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- press an arrow key without shift
   edit.run_after_keychord(Editor_state, 'right', 'right')
@@ -565,7 +546,6 @@ function test_copy_does_not_reset_selection()
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.selection1 = {line=1, pos=2}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- copy selection
   edit.run_after_keychord(Editor_state, 'C-c', 'c')
@@ -575,15 +555,15 @@ function test_copy_does_not_reset_selection()
 end
 
 function test_move_cursor_using_mouse()
+
   App.screen.init{width=50, height=60}
   Editor_state = edit.initialize_test_state()
   Editor_state.lines = load_array{'abc', 'def', 'xyz'}
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
-  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
+  edit.draw(Editor_state)  -- populate line_cache.startpos for each line
   edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
   check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
   check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
@@ -598,9 +578,8 @@ function test_select_text_using_mouse()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
-  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
+  edit.draw(Editor_state)  -- populate line_cache.startpos for each line
   -- press and hold on first location
   edit.run_after_mouse_press(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
   -- drag and release somewhere else
@@ -618,9 +597,8 @@ function test_select_text_using_mouse_starting_above_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
-  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
+  edit.draw(Editor_state)  -- populate line_cache.startpos for each line
   -- press mouse above first line of text
   edit.run_after_mouse_press(Editor_state, Editor_state.left+8,5, 1)
   check(Editor_state.selection1.line ~= nil, 'selection:line-not-nil')
@@ -636,7 +614,6 @@ function test_select_text_using_mouse_starting_above_text_wrapping_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=5}
   Editor_state.screen_top1 = {line=2, pos=3}
-  Editor_state.screen_bottom1 = {}
   -- press mouse above first line of text
   edit.draw(Editor_state)
   edit.run_after_mouse_press(Editor_state, Editor_state.left+8,5, 1)
@@ -659,7 +636,6 @@ function test_select_text_using_mouse_starting_below_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'ab', 'baseline:screen:1')
@@ -680,9 +656,8 @@ function test_select_text_using_mouse_and_shift()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
-  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
+  edit.draw(Editor_state)  -- populate line_cache.startpos for each line
   -- click on first location
   edit.run_after_mouse_press(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
   edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
@@ -705,9 +680,8 @@ function test_select_text_repeatedly_using_mouse_and_shift()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   Editor_state.selection1 = {}
-  edit.draw(Editor_state)  -- populate line_cache.starty for each line Editor_state.line_cache
+  edit.draw(Editor_state)  -- populate line_cache.startpos for each line
   -- click on first location
   edit.run_after_mouse_press(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
   edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
@@ -735,7 +709,6 @@ function test_select_all_text()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- select all
   App.fake_key_press('lctrl')
@@ -756,7 +729,6 @@ function test_pagedown()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- initially the first two lines are displayed
   edit.draw(Editor_state)
   local y = Editor_state.top
@@ -773,36 +745,6 @@ function test_pagedown()
   App.screen.check(y, 'ghi', 'screen:2')
 end
 
-function test_pagedown_often_shows_start_of_wrapping_line()
-  -- draw a few lines ending in part of a wrapping line
-  App.screen.init{width=50, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'def ghi jkl', 'mno'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=1}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  local y = Editor_state.top
-  App.screen.check(y, 'abc', 'baseline/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'def ', 'baseline/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'ghi ', 'baseline/screen:3')
-  -- after pagedown we start drawing from the bottom _line_ (multiple screen lines)
-  edit.run_after_keychord(Editor_state, 'pagedown', 'pagedown')
-  check_eq(Editor_state.screen_top1.line, 2, 'screen_top:line')
-  check_eq(Editor_state.screen_top1.pos, 1, 'screen_top:pos')
-  check_eq(Editor_state.cursor1.line, 2, 'cursor:line')
-  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
-  y = Editor_state.top
-  App.screen.check(y, 'def ', 'screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'ghi ', 'screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'jkl', 'screen:3')
-end
-
 function test_pagedown_can_start_from_middle_of_long_wrapping_line()
   -- draw a few lines starting from a very long wrapping line
   App.screen.init{width=Editor_state.left+30, height=60}
@@ -811,7 +753,6 @@ function test_pagedown_can_start_from_middle_of_long_wrapping_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=2}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc ', 'baseline/screen:1')
@@ -846,7 +787,6 @@ function test_pagedown_never_moves_up()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=9}
   Editor_state.screen_top1 = {line=1, pos=9}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- pagedown makes no change
   edit.run_after_keychord(Editor_state, 'pagedown', 'pagedown')
@@ -861,7 +801,6 @@ function test_down_arrow_moves_cursor()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- initially the first three lines are displayed
   edit.draw(Editor_state)
   local y = Editor_state.top
@@ -891,7 +830,6 @@ function test_down_arrow_scrolls_down_by_one_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -919,7 +857,6 @@ function test_down_arrow_scrolls_down_by_one_screen_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -948,7 +885,6 @@ function test_down_arrow_scrolls_down_by_one_screen_line_after_splitting_within_
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -976,7 +912,6 @@ function test_pagedown_followed_by_down_arrow_does_not_scroll_screen_up()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -1010,7 +945,6 @@ function test_up_arrow_moves_cursor()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -1039,7 +973,6 @@ function test_up_arrow_scrolls_up_by_one_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'def', 'baseline/screen:1')
@@ -1067,7 +1000,6 @@ function test_up_arrow_scrolls_up_by_one_screen_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=3, pos=6}
   Editor_state.screen_top1 = {line=3, pos=5}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'jkl', 'baseline/screen:1')
@@ -1095,7 +1027,6 @@ function test_up_arrow_scrolls_up_to_final_screen_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'ghi', 'baseline/screen:1')
@@ -1125,7 +1056,6 @@ function test_up_arrow_scrolls_up_to_empty_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'abc', 'baseline/screen:1')
@@ -1152,7 +1082,6 @@ function test_pageup()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- initially the last two lines are displayed
   edit.draw(Editor_state)
   local y = Editor_state.top
@@ -1177,7 +1106,6 @@ function test_pageup_scrolls_up_by_screen_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'ghi', 'baseline/screen:1')
@@ -1206,7 +1134,6 @@ function test_pageup_scrolls_up_from_middle_screen_line()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=5}
   Editor_state.screen_top1 = {line=2, pos=5}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   local y = Editor_state.top
   App.screen.check(y, 'jkl', 'baseline/screen:2')
@@ -1232,7 +1159,6 @@ function test_left_arrow_scrolls_up_in_wrapped_line()
   Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
   Text.redraw_all(Editor_state)
   Editor_state.screen_top1 = {line=3, pos=5}
-  Editor_state.screen_bottom1 = {}
   -- cursor is at top of screen
   Editor_state.cursor1 = {line=3, pos=5}
   edit.draw(Editor_state)
@@ -1261,7 +1187,6 @@ function test_right_arrow_scrolls_down_in_wrapped_line()
   Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
   Text.redraw_all(Editor_state)
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- cursor is at bottom right of screen
   Editor_state.cursor1 = {line=3, pos=5}
   edit.draw(Editor_state)
@@ -1291,7 +1216,6 @@ function test_home_scrolls_up_in_wrapped_line()
   Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
   Text.redraw_all(Editor_state)
   Editor_state.screen_top1 = {line=3, pos=5}
-  Editor_state.screen_bottom1 = {}
   -- cursor is at top of screen
   Editor_state.cursor1 = {line=3, pos=5}
   edit.draw(Editor_state)
@@ -1320,7 +1244,6 @@ function test_end_scrolls_down_in_wrapped_line()
   Editor_state.lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
   Text.redraw_all(Editor_state)
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   -- cursor is at bottom right of screen
   Editor_state.cursor1 = {line=3, pos=5}
   edit.draw(Editor_state)
@@ -1350,7 +1273,6 @@ function test_search()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- search for a string
   edit.run_after_keychord(Editor_state, 'C-f', 'f')
@@ -1377,7 +1299,6 @@ function test_search_upwards()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- search for a string
   edit.run_after_keychord(Editor_state, 'C-f', 'f')
@@ -1395,7 +1316,6 @@ function test_search_wrap()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=2, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- search for a string
   edit.run_after_keychord(Editor_state, 'C-f', 'f')
@@ -1413,7 +1333,6 @@ function test_search_wrap_upwards()
   Text.redraw_all(Editor_state)
   Editor_state.cursor1 = {line=1, pos=1}
   Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
   edit.draw(Editor_state)
   -- search upwards for a string
   edit.run_after_keychord(Editor_state, 'C-f', 'f')