several more modules

This is probably not ideal; let's see how it goes..

6 files changed, 707 insertions, 697 deletions

diff --git a/drawing.lua b/drawing.lua
index 928325f..30182a2 100644
--- a/drawing.lua
+++ b/drawing.lua
@@ -1,15 +1,16 @@
 -- primitives for editing drawings
 Drawing = {}
+geom = require 'geom'
 
 function Drawing.draw(line, y)
   local pmx,pmy = love.mouse.getX(), love.mouse.getY()
-  if pmx < 16+Drawing_width and pmy > line.y and pmy < line.y+pixels(line.h) then
+  if pmx < 16+Drawing_width and pmy > line.y and pmy < line.y+Drawing.pixels(line.h) then
     love.graphics.setColor(0.75,0.75,0.75)
-    love.graphics.rectangle('line', 16,line.y, Drawing_width,pixels(line.h))
-    if icon[Current_mode] then
-      icon[Current_mode](16+Drawing_width-20, line.y+4)
+    love.graphics.rectangle('line', 16,line.y, Drawing_width,Drawing.pixels(line.h))
+    if icon[Current_drawing_mode] then
+      icon[Current_drawing_mode](16+Drawing_width-20, line.y+4)
     else
-      icon[Previous_mode](16+Drawing_width-20, line.y+4)
+      icon[Previous_drawing_mode](16+Drawing_width-20, line.y+4)
     end
 
     if love.mouse.isDown('1') and love.keyboard.isDown('h') then
@@ -23,29 +24,260 @@ function Drawing.draw(line, y)
     return
   end
 
-  local mx,my = coord(love.mouse.getX()-16), coord(love.mouse.getY()-line.y)
+  local mx,my = Drawing.coord(love.mouse.getX()-16), Drawing.coord(love.mouse.getY()-line.y)
 
   for _,shape in ipairs(line.shapes) do
     assert(shape)
-    if on_shape(mx,my, line, shape) then
+    if geom.on_shape(mx,my, line, shape) then
       love.graphics.setColor(1,0,0)
     else
       love.graphics.setColor(0,0,0)
     end
-    draw_shape(16,line.y, line, shape)
+    Drawing.draw_shape(16,line.y, line, shape)
   end
   for _,p in ipairs(line.points) do
     if p.deleted == nil then
-      if near(p, mx,my) then
+      if Drawing.near(p, mx,my) then
         love.graphics.setColor(1,0,0)
-        love.graphics.circle('line', pixels(p.x)+16,pixels(p.y)+line.y, 4)
+        love.graphics.circle('line', Drawing.pixels(p.x)+16,Drawing.pixels(p.y)+line.y, 4)
       else
         love.graphics.setColor(0,0,0)
-        love.graphics.circle('fill', pixels(p.x)+16,pixels(p.y)+line.y, 2)
+        love.graphics.circle('fill', Drawing.pixels(p.x)+16,Drawing.pixels(p.y)+line.y, 2)
       end
     end
   end
-  draw_pending_shape(16,line.y, line)
+  Drawing.draw_pending_shape(16,line.y, line)
+end
+
+function Drawing.current_drawing()
+  local x, y = love.mouse.getX(), love.mouse.getY()
+  for _,drawing in ipairs(Lines) do
+    if drawing.mode == 'drawing' then
+      if y >= drawing.y and y < drawing.y + Drawing.pixels(drawing.h) and x >= 16 and x < 16+Drawing_width then
+        return drawing
+      end
+    end
+  end
+  return nil
+end
+
+function Drawing.select_shape_at_mouse()
+  for _,drawing in ipairs(Lines) do
+    if drawing.mode == 'drawing' then
+      local x, y = love.mouse.getX(), love.mouse.getY()
+      if y >= drawing.y and y < drawing.y + Drawing.pixels(drawing.h) and x >= 16 and x < 16+Drawing_width then
+        local mx,my = Drawing.coord(love.mouse.getX()-16), Drawing.coord(love.mouse.getY()-drawing.y)
+        for i,shape in ipairs(drawing.shapes) do
+          assert(shape)
+          if geom.on_shape(mx,my, drawing, shape) then
+            return drawing,i,shape
+          end
+        end
+      end
+    end
+  end
+end
+
+function Drawing.select_point_at_mouse()
+  for _,drawing in ipairs(Lines) do
+    if drawing.mode == 'drawing' then
+      local x, y = love.mouse.getX(), love.mouse.getY()
+      if y >= drawing.y and y < drawing.y + Drawing.pixels(drawing.h) and x >= 16 and x < 16+Drawing_width then
+        local mx,my = Drawing.coord(love.mouse.getX()-16), Drawing.coord(love.mouse.getY()-drawing.y)
+        for i,point in ipairs(drawing.points) do
+          assert(point)
+          if Drawing.near(point, mx,my) then
+            return drawing,i,point
+          end
+        end
+      end
+    end
+  end
+end
+
+function Drawing.select_drawing_at_mouse()
+  for _,drawing in ipairs(Lines) do
+    if drawing.mode == 'drawing' then
+      local x, y = love.mouse.getX(), love.mouse.getY()
+      if y >= drawing.y and y < drawing.y + Drawing.pixels(drawing.h) and x >= 16 and x < 16+Drawing_width then
+        return drawing
+      end
+    end
+  end
+end
+
+function Drawing.contains_point(shape, p)
+  if shape.mode == 'freehand' then
+    -- not supported
+  elseif shape.mode == 'line' or shape.mode == 'manhattan' then
+    return shape.p1 == p or shape.p2 == p
+  elseif shape.mode == 'polygon' then
+    return table.find(shape.vertices, p)
+  elseif shape.mode == 'circle' then
+    return shape.center == p
+  elseif shape.mode == 'arc' then
+    return shape.center == p
+    -- ugh, how to support angles
+  elseif shape.mode == 'deleted' then
+    -- already done
+  else
+    print(shape.mode)
+    assert(false)
+  end
+end
+
+function Drawing.convert_line(drawing, shape)
+  -- Perhaps we should do a more sophisticated "simple linear regression"
+  -- here:
+  --   https://en.wikipedia.org/wiki/Linear_regression#Simple_and_multiple_linear_regression
+  -- But this works well enough for close-to-linear strokes.
+  assert(shape.mode == 'freehand')
+  shape.mode = 'line'
+  shape.p1 = insert_point(drawing.points, shape.points[1].x, shape.points[1].y)
+  local n = #shape.points
+  shape.p2 = insert_point(drawing.points, shape.points[n].x, shape.points[n].y)
+end
+
+-- turn a line either horizontal or vertical
+function Drawing.convert_horvert(drawing, shape)
+  if shape.mode == 'freehand' then
+    convert_line(shape)
+  end
+  assert(shape.mode == 'line')
+  local p1 = drawing.points[shape.p1]
+  local p2 = drawing.points[shape.p2]
+  if math.abs(p1.x-p2.x) > math.abs(p1.y-p2.y) then
+    p2.y = p1.y
+  else
+    p2.x = p1.x
+  end
+end
+
+function Drawing.smoothen(shape)
+  assert(shape.mode == 'freehand')
+  for _=1,7 do
+    for i=2,#shape.points-1 do
+      local a = shape.points[i-1]
+      local b = shape.points[i]
+      local c = shape.points[i+1]
+      b.x = (a.x + b.x + c.x)/3
+      b.y = (a.y + b.y + c.y)/3
+    end
+  end
+end
+
+function Drawing.insert_point(points, x,y)
+  for i,point in ipairs(points) do
+    if Drawing.near(point, x,y) then
+      return i
+    end
+  end
+  table.insert(points, {x=x, y=y})
+  return #points
+end
+
+function Drawing.near(point, x,y)
+  local px,py = Drawing.pixels(x),Drawing.pixels(y)
+  local cx,cy = Drawing.pixels(point.x), Drawing.pixels(point.y)
+  return (cx-px)*(cx-px) + (cy-py)*(cy-py) < 16
+end
+
+function Drawing.draw_shape(left,top, drawing, shape)
+  if shape.mode == 'freehand' then
+    local prev = nil
+    for _,point in ipairs(shape.points) do
+      if prev then
+        love.graphics.line(Drawing.pixels(prev.x)+left,Drawing.pixels(prev.y)+top, Drawing.pixels(point.x)+left,Drawing.pixels(point.y)+top)
+      end
+      prev = point
+    end
+  elseif shape.mode == 'line' or shape.mode == 'manhattan' then
+    local p1 = drawing.points[shape.p1]
+    local p2 = drawing.points[shape.p2]
+    love.graphics.line(Drawing.pixels(p1.x)+left,Drawing.pixels(p1.y)+top, Drawing.pixels(p2.x)+left,Drawing.pixels(p2.y)+top)
+  elseif shape.mode == 'polygon' then
+    local prev = nil
+    for _,point in ipairs(shape.vertices) do
+      local curr = drawing.points[point]
+      if prev then
+        love.graphics.line(Drawing.pixels(prev.x)+left,Drawing.pixels(prev.y)+top, Drawing.pixels(curr.x)+left,Drawing.pixels(curr.y)+top)
+      end
+      prev = curr
+    end
+    -- close the loop
+    local curr = drawing.points[shape.vertices[1]]
+    love.graphics.line(Drawing.pixels(prev.x)+left,Drawing.pixels(prev.y)+top, Drawing.pixels(curr.x)+left,Drawing.pixels(curr.y)+top)
+  elseif shape.mode == 'circle' then
+    local center = drawing.points[shape.center]
+    love.graphics.circle('line', Drawing.pixels(center.x)+left,Drawing.pixels(center.y)+top, Drawing.pixels(shape.radius))
+  elseif shape.mode == 'arc' then
+    local center = drawing.points[shape.center]
+    love.graphics.arc('line', 'open', Drawing.pixels(center.x)+left,Drawing.pixels(center.y)+top, Drawing.pixels(shape.radius), shape.start_angle, shape.end_angle, 360)
+  elseif shape.mode == 'deleted' then
+  else
+    print(shape.mode)
+    assert(false)
+  end
+end
+
+function Drawing.draw_pending_shape(left,top, drawing)
+  local shape = drawing.pending
+  if shape.mode == 'freehand' then
+    draw_shape(left,top, drawing, shape)
+  elseif shape.mode == 'line' then
+    local p1 = drawing.points[shape.p1]
+    local mx,my = Drawing.coord(love.mouse.getX()-16), Drawing.coord(love.mouse.getY()-drawing.y)
+    if mx < 0 or mx >= 256 or my < 0 or my >= drawing.h then
+      return
+    end
+    love.graphics.line(Drawing.pixels(p1.x)+left,Drawing.pixels(p1.y)+top, Drawing.pixels(mx)+left,Drawing.pixels(my)+top)
+  elseif shape.mode == 'manhattan' then
+    local p1 = drawing.points[shape.p1]
+    local mx,my = Drawing.coord(love.mouse.getX()-16), Drawing.coord(love.mouse.getY()-drawing.y)
+    if mx < 0 or mx >= 256 or my < 0 or my >= drawing.h then
+      return
+    end
+    if math.abs(mx-p1.x) > math.abs(my-p1.y) then
+      love.graphics.line(Drawing.pixels(p1.x)+left,Drawing.pixels(p1.y)+top, Drawing.pixels(mx)+left,Drawing.pixels(p1.y)+top)
+    else
+      love.graphics.line(Drawing.pixels(p1.x)+left,Drawing.pixels(p1.y)+top, Drawing.pixels(p1.x)+left,Drawing.pixels(my)+top)
+    end
+  elseif shape.mode == 'polygon' then
+    -- don't close the loop on a pending polygon
+    local prev = nil
+    for _,point in ipairs(shape.vertices) do
+      local curr = drawing.points[point]
+      if prev then
+        love.graphics.line(Drawing.pixels(prev.x)+left,Drawing.pixels(prev.y)+top, Drawing.pixels(curr.x)+left,Drawing.pixels(curr.y)+top)
+      end
+      prev = curr
+    end
+    love.graphics.line(Drawing.pixels(prev.x)+left,Drawing.pixels(prev.y)+top, love.mouse.getX(),love.mouse.getY())
+  elseif shape.mode == 'circle' then
+    local center = drawing.points[shape.center]
+    local mx,my = Drawing.coord(love.mouse.getX()-16), Drawing.coord(love.mouse.getY()-drawing.y)
+    if mx < 0 or mx >= 256 or my < 0 or my >= drawing.h then
+      return
+    end
+    local cx,cy = Drawing.pixels(center.x)+left, Drawing.pixels(center.y)+top
+    love.graphics.circle('line', cx,cy, math.dist(cx,cy, love.mouse.getX(),love.mouse.getY()))
+  elseif shape.mode == 'arc' then
+    local center = drawing.points[shape.center]
+    local mx,my = Drawing.coord(love.mouse.getX()-16), Drawing.coord(love.mouse.getY()-drawing.y)
+    if mx < 0 or mx >= 256 or my < 0 or my >= drawing.h then
+      return
+    end
+    shape.end_angle = geom.angle_with_hint(center.x,center.y, mx,my, shape.end_angle)
+    local cx,cy = Drawing.pixels(center.x)+left, Drawing.pixels(center.y)+top
+    love.graphics.arc('line', 'open', cx,cy, Drawing.pixels(shape.radius), shape.start_angle, shape.end_angle, 360)
+  end
+end
+
+function Drawing.pixels(n)  -- parts to pixels
+  return n*Drawing_width/256
+end
+function Drawing.coord(n)  -- pixels to parts
+  return math.floor(n*256/Drawing_width)
 end
 
 return Drawing
diff --git a/file.lua b/file.lua
new file mode 100644
index 0000000..c305869
--- /dev/null
+++ b/file.lua
@@ -0,0 +1,88 @@
+-- primitives for saving to file and loading from file
+Drawing = require 'drawing'
+
+function load_from_disk(filename)
+  local infile = io.open(filename)
+  local result = load_from_file(infile)
+  if infile then infile:close() end
+  return result
+end
+
+function load_from_file(infile)
+  local result = {}
+  if infile then
+    local infile_next_line = infile:lines()  -- works with both Lua files and LÖVE Files (https://www.love2d.org/wiki/File)
+    while true do
+      local line = infile_next_line()
+      if line == nil then break end
+      if line == '```lines' then  -- inflexible with whitespace since these files are always autogenerated
+        table.insert(result, load_drawing(infile_next_line))
+      else
+        table.insert(result, {mode='text', data=line})
+      end
+    end
+  end
+  if #result == 0 then
+    table.insert(result, {mode='text', data=''})
+  end
+  return result
+end
+
+function save_to_disk(lines, filename)
+  local outfile = io.open(filename, 'w')
+  for _,line in ipairs(lines) do
+    if line.mode == 'drawing' then
+      store_drawing(outfile, line)
+    else
+      outfile:write(line.data..'\n')
+    end
+  end
+  outfile:close()
+end
+
+json = require 'json'
+function load_drawing(infile_next_line)
+  local drawing = {mode='drawing', h=256/2, points={}, shapes={}, pending={}}
+  while true do
+    local line = infile_next_line()
+    assert(line)
+    if line == '```' then break end
+    local shape = json.decode(line)
+    if shape.mode == 'line' or shape.mode == 'manhattan' then
+      shape.p1 = Drawing.insert_point(drawing.points, shape.p1.x, shape.p1.y)
+      shape.p2 = Drawing.insert_point(drawing.points, shape.p2.x, shape.p2.y)
+    elseif shape.mode == 'polygon' then
+      for i,p in ipairs(shape.vertices) do
+        shape.vertices[i] = Drawing.insert_point(drawing.points, p.x,p.y)
+      end
+    elseif shape.mode == 'circle' or shape.mode == 'arc' then
+      shape.center = Drawing.insert_point(drawing.points, shape.center.x,shape.center.y)
+    end
+    table.insert(drawing.shapes, shape)
+  end
+  return drawing
+end
+
+function store_drawing(outfile, drawing)
+  outfile:write('```lines\n')
+  for _,shape in ipairs(drawing.shapes) do
+    if shape.mode == 'freehand' then
+      outfile:write(json.encode(shape)..'\n')
+    elseif shape.mode == 'line' or shape.mode == 'manhattan' then
+      local line = json.encode({mode=shape.mode, p1=drawing.points[shape.p1], p2=drawing.points[shape.p2]})
+      outfile:write(line..'\n')
+    elseif shape.mode == 'polygon' then
+      local obj = {mode=shape.mode, vertices={}}
+      for _,p in ipairs(shape.vertices) do
+        table.insert(obj.vertices, drawing.points[p])
+      end
+      local line = json.encode(obj)
+      outfile:write(line..'\n')
+    elseif shape.mode == 'circle' then
+      outfile:write(json.encode({mode=shape.mode, center=drawing.points[shape.center], radius=shape.radius})..'\n')
+    elseif shape.mode == 'arc' then
+      outfile:write(json.encode({mode=shape.mode, center=drawing.points[shape.center], radius=shape.radius, start_angle=shape.start_angle, end_angle=shape.end_angle})..'\n')
+    end
+  end
+  outfile:write('```\n')
+end
diff --git a/geom.lua b/geom.lua
new file mode 100644
index 0000000..7b71df3
--- /dev/null
+++ b/geom.lua
@@ -0,0 +1,131 @@
+local geom = {}
+
+function geom.on_shape(x,y, drawing, shape)
+  if shape.mode == 'freehand' then
+    return geom.on_freehand(x,y, drawing, shape)
+  elseif shape.mode == 'line' then
+    return geom.on_line(x,y, drawing, shape)
+  elseif shape.mode == 'manhattan' then
+    return x == drawing.points[shape.p1].x or y == drawing.points[shape.p1].y
+  elseif shape.mode == 'polygon' then
+    return geom.on_polygon(x,y, drawing, shape)
+  elseif shape.mode == 'circle' then
+    local center = drawing.points[shape.center]
+    return math.dist(center.x,center.y, x,y) == shape.radius
+  elseif shape.mode == 'arc' then
+    local center = drawing.points[shape.center]
+    local dist = math.dist(center.x,center.y, x,y)
+    if dist < shape.radius*0.95 or dist > shape.radius*1.05 then
+      return false
+    end
+    return geom.angle_between(center.x,center.y, x,y, shape.start_angle,shape.end_angle)
+  elseif shape.mode == 'deleted' then
+  else
+    print(shape.mode)
+    assert(false)
+  end
+end
+
+function geom.on_freehand(x,y, drawing, shape)
+  local prev
+  for _,p in ipairs(shape.points) do
+    if prev then
+      if geom.on_line(x,y, drawing, {p1=prev, p2=p}) then
+        return true
+      end
+    end
+    prev = p
+  end
+  return false
+end
+
+function geom.on_line(x,y, drawing, shape)
+  local p1,p2
+  if type(shape.p1) == 'number' then
+    p1 = drawing.points[shape.p1]
+    p2 = drawing.points[shape.p2]
+  else
+    p1 = shape.p1
+    p2 = shape.p2
+  end
+  if p1.x == p2.x then
+    if math.abs(p1.x-x) > 5 then
+      return false
+    end
+    local y1,y2 = p1.y,p2.y
+    if y1 > y2 then
+      y1,y2 = y2,y1
+    end
+    return y >= y1 and y <= y2
+  end
+  -- has the right slope and intercept
+  local m = (p2.y - p1.y) / (p2.x - p1.x)
+  local yp = p1.y + m*(x-p1.x)
+  if yp < 0.95*y or yp > 1.05*y then
+    return false
+  end
+  -- between endpoints
+  local k = (x-p1.x) / (p2.x-p1.x)
+  return k > -0.05 and k < 1.05
+end
+
+function geom.on_polygon(x,y, drawing, shape)
+  local prev
+  for _,p in ipairs(shape.vertices) do
+    if prev then
+      if geom.on_line(x,y, drawing, {p1=prev, p2=p}) then
+        return true
+      end
+    end
+    prev = p
+  end
+  return geom.on_line(x,y, drawing, {p1=shape.vertices[1], p2=shape.vertices[#shape.vertices]})
+end
+
+function geom.angle_with_hint(x1, y1, x2, y2, hint)
+  local result = geom.angle(x1,y1, x2,y2)
+  if hint then
+    -- Smooth the discontinuity where angle goes from positive to negative.
+    -- The hint is a memory of which way we drew it last time.
+    while result > hint+math.pi/10 do
+      result = result-math.pi*2
+    end
+    while result < hint-math.pi/10 do
+      result = result+math.pi*2
+    end
+  end
+  return result
+end
+
+-- result is from -π/2 to 3π/2, approximately adding math.atan2 from Lua 5.3
+-- (LÖVE is Lua 5.1)
+function geom.angle(x1,y1, x2,y2)
+  local result = math.atan((y2-y1)/(x2-x1))
+  if x2 < x1 then
+    result = result+math.pi
+  end
+  return result
+end
+
+-- is the line between x,y and cx,cy at an angle between s and e?
+function geom.angle_between(ox,oy, x,y, s,e)
+  local angle = math.angle(ox,oy, x,y)
+  if s > e then
+    s,e = e,s
+  end
+  -- I'm not sure this is right or ideal..
+  angle = angle-math.pi*2
+  if s <= angle and angle <= e then
+    return true
+  end
+  angle = angle+math.pi*2
+  if s <= angle and angle <= e then
+    return true
+  end
+  angle = angle+math.pi*2
+  return s <= angle and angle <= e
+end
+
+function geom.dist(x1,y1, x2,y2) return ((x2-x1)^2+(y2-y1)^2)^0.5 end
+
+return geom
diff --git a/help.lua b/help.lua
new file mode 100644
index 0000000..0feaba1
--- /dev/null
+++ b/help.lua
@@ -0,0 +1,118 @@
+function draw_help_without_mouse_pressed(drawing)
+  love.graphics.setColor(0,0.5,0)
+  local y = drawing.y+10
+  love.graphics.print("Things you can do:", 16+30,y, 0, Zoom)
+  y = y+15*Zoom
+  love.graphics.print("* Press the mouse button to start drawing a "..current_shape(), 16+30,y, 0, Zoom)
+  y = y+15*Zoom
+  love.graphics.print("* Hover on a point and press 'ctrl+v' to start moving it,", 16+30,y, 0, Zoom)
+  y = y+15*Zoom
+  love.graphics.print("then press the mouse button to finish", 16+30+bullet_indent(),y, 0, Zoom)
+  y = y+15*Zoom
+  love.graphics.print("* Hover on a point or shape and press 'ctrl+d' to delete it", 16+30,y, 0, Zoom)
+  y = y+15*Zoom
+  y = y+15*Zoom
+  if Current_drawing_mode ~= 'freehand' then
+    love.graphics.print("* Press 'ctrl+f' to switch to drawing freehand strokes", 16+30,y, 0, Zoom)
+    y = y+15*Zoom
+  end
+  if Current_drawing_mode ~= 'line' then
+    love.graphics.print("* Press 'ctrl+l' to switch to drawing lines", 16+30,y, 0, Zoom)
+    y = y+15*Zoom
+  end
+  if Current_drawing_mode ~= 'manhattan' then
+    love.graphics.print("* Press 'ctrl+m' to switch to drawing horizontal/vertical lines", 16+30,y, 0, Zoom)
+    y = y+15*Zoom
+  end
+  if Current_drawing_mode ~= 'circle' then
+    love.graphics.print("* Press 'ctrl+c' to switch to drawing circles/arcs", 16+30,y, 0, Zoom)
+    y = y+15*Zoom
+  end
+  if Current_drawing_mode ~= 'polygon' then
+    love.graphics.print("* Press 'ctrl+g' to switch to drawing polygons", 16+30,y, 0, Zoom)
+    y = y+15*Zoom
+  end
+  love.graphics.print("* Press 'ctrl+=' or 'ctrl+-' to Zoom in or out", 16+30,y, 0, Zoom)
+  y = y+15*Zoom
+  love.graphics.print("* Press 'ctrl+0' to reset Zoom", 16+30,y, 0, Zoom)
+  y = y+15*Zoom
+  y = y+15*Zoom
+  love.graphics.print("Hit 'esc' now to hide this message", 16+30,y, 0, Zoom)
+  y = y+15*Zoom
+  love.graphics.setColor(0,0.5,0, 0.1)
+  love.graphics.rectangle('fill', 16,drawing.y, Drawing_width, math.max(Drawing.pixels(drawing.h),y-drawing.y))
+end
+
+function draw_help_with_mouse_pressed(drawing)
+  love.graphics.setColor(0,0.5,0)
+  local y = drawing.y+10
+  love.graphics.print("You're currently drawing a "..current_shape(drawing.pending), 16+30,y, 0, Zoom)
+  y = y+15*Zoom
+  love.graphics.print('Things you can do now:', 16+30,y, 0, Zoom)
+  y = y+15*Zoom
+  if Current_drawing_mode == 'freehand' then
+    love.graphics.print('* Release the mouse button to finish drawing the stroke', 16+30,y, 0, Zoom)
+    y = y+15*Zoom
+  elseif Current_drawing_mode == 'line' or Current_drawing_mode == 'manhattan' then
+    love.graphics.print('* Release the mouse button to finish drawing the line', 16+30,y, 0, Zoom)
+    y = y+15*Zoom
+  elseif Current_drawing_mode == 'circle' then
+    if drawing.pending.mode == 'circle' then
+      love.graphics.print('* Release the mouse button to finish drawing the circle', 16+30,y, 0, Zoom)
+      y = y+15*Zoom
+      love.graphics.print("* Press 'a' to draw just an arc of a circle", 16+30,y, 0, Zoom)
+    else
+      love.graphics.print('* Release the mouse button to finish drawing the arc', 16+30,y, 0, Zoom)
+    end
+    y = y+15*Zoom
+  elseif Current_drawing_mode == 'polygon' then
+    love.graphics.print('* Release the mouse button to finish drawing the polygon', 16+30,y, 0, Zoom)
+    y = y+15*Zoom
+    love.graphics.print("* Press 'p' to add a vertex to the polygon", 16+30,y, 0, Zoom)
+    y = y+15*Zoom
+  end
+  love.graphics.print("* Press 'esc' then release the mouse button to cancel the current shape", 16+30,y, 0, Zoom)
+  y = y+15*Zoom
+  y = y+15*Zoom
+  if Current_drawing_mode ~= 'line' then
+    love.graphics.print("* Press 'l' to switch to drawing lines", 16+30,y, 0, Zoom)
+    y = y+15*Zoom
+  end
+  if Current_drawing_mode ~= 'manhattan' then
+    love.graphics.print("* Press 'm' to switch to drawing horizontal/vertical lines", 16+30,y, 0, Zoom)
+    y = y+15*Zoom
+  end
+  if Current_drawing_mode ~= 'circle' then
+    love.graphics.print("* Press 'c' to switch to drawing circles/arcs", 16+30,y, 0, Zoom)
+    y = y+15*Zoom
+  end
+  if Current_drawing_mode ~= 'polygon' then
+    love.graphics.print("* Press 'g' to switch to drawing polygons", 16+30,y, 0, Zoom)
+    y = y+15*Zoom
+  end
+  love.graphics.setColor(0,0.5,0, 0.1)
+  love.graphics.rectangle('fill', 16,drawing.y, Drawing_width, math.max(Drawing.pixels(drawing.h),y-drawing.y))
+end
+
+function current_shape(shape)
+  if Current_drawing_mode == 'freehand' then
+    return 'freehand stroke'
+  elseif Current_drawing_mode == 'line' then
+    return 'straight line'
+  elseif Current_drawing_mode == 'manhattan' then
+    return 'horizontal/vertical line'
+  elseif Current_drawing_mode == 'circle' and shape and shape.start_angle then
+    return 'arc'
+  else
+    return Current_drawing_mode
+  end
+end
+
+_bullet_indent = nil
+function bullet_indent()
+  if _bullet_indent == nil then
+    local text = love.graphics.newText(love.graphics.getFont(), '* ')
+    _bullet_indent = text:getWidth()
+  end
+  return _bullet_indent
+end
diff --git a/icons.lua b/icons.lua
new file mode 100644
index 0000000..0d05d09
--- /dev/null
+++ b/icons.lua
@@ -0,0 +1,45 @@
+icon = {}
+
+function icon.insert_drawing(x, y)
+  love.graphics.setColor(0.7,0.7,0.7)
+  love.graphics.rectangle('line', x,y, 12,12)
+  love.graphics.line(4,y+6, 16,y+6)
+  love.graphics.line(10,y, 10,y+12)
+  love.graphics.setColor(0, 0, 0)
+end
+
+function icon.freehand(x, y)
+  love.graphics.line(x+4,y+7,x+5,y+5)
+  love.graphics.line(x+5,y+5,x+7,y+4)
+  love.graphics.line(x+7,y+4,x+9,y+3)
+  love.graphics.line(x+9,y+3,x+10,y+5)
+  love.graphics.line(x+10,y+5,x+12,y+6)
+  love.graphics.line(x+12,y+6,x+13,y+8)
+  love.graphics.line(x+13,y+8,x+13,y+10)
+  love.graphics.line(x+13,y+10,x+14,y+12)
+  love.graphics.line(x+14,y+12,x+15,y+14)
+  love.graphics.line(x+15,y+14,x+15,y+16)
+end
+
+function icon.line(x, y)
+  love.graphics.line(x+4,y+2, x+16,y+18)
+end
+
+function icon.manhattan(x, y)
+  love.graphics.line(x+4,y+20, x+4,y+2)
+  love.graphics.line(x+4,y+2, x+10,y+2)
+  love.graphics.line(x+10,y+2, x+10,y+10)
+  love.graphics.line(x+10,y+10, x+18,y+10)
+end
+
+function icon.polygon(x, y)
+  love.graphics.line(x+8,y+2, x+14,y+2)
+  love.graphics.line(x+14,y+2, x+18,y+10)
+  love.graphics.line(x+18,y+10, x+10,y+18)
+  love.graphics.line(x+10,y+18, x+4,y+12)
+  love.graphics.line(x+4,y+12, x+8,y+2)
+end
+
+function icon.circle(x, y)
+  love.graphics.circle('line', x+10,y+10, 8)
+end
diff --git a/main.lua b/main.lua
index 3ef933c..a5cd066 100644
--- a/main.lua
+++ b/main.lua
@@ -1,8 +1,12 @@
 local utf8 = require 'utf8'
 require 'keychord'
+require 'file'
 require 'button'
 local Text = require 'text'
 local Drawing = require 'drawing'
+local geom = require 'geom'
+require 'help'
+require 'icons'
 
 -- a line is either text or a drawing
 -- a text is a table with:
@@ -42,18 +46,12 @@ Cursor_pos = #Lines[Cursor_line].data+1
 
 Screen_width, Screen_height, Screen_flags = 0, 0, nil
 
-Current_mode = 'line'
-Previous_mode = nil
+Current_drawing_mode = 'line'
+Previous_drawing_mode = nil
 
 -- All drawings span 100% of some conceptual 'page width' and divide it up
 -- into 256 parts. `Drawing_width` describes their width in pixels.
 Drawing_width = nil  -- pixels
-function pixels(n)  -- parts to pixels
-  return n*Drawing_width/256
-end
-function coord(n)  -- pixels to parts
-  return math.floor(n*256/Drawing_width)
-end
 
 Zoom = 1.5
 
@@ -118,7 +116,7 @@ function love.draw()
           love.graphics.print('_', 25, y+6)  -- drop the cursor down a bit to account for the increased font size
         end
     elseif line.mode == 'drawing' then
-      y = y+pixels(line.h)
+      y = y+Drawing.pixels(line.h)
       Drawing.draw(line, y)
     else
       Text.draw(line, line_index, Cursor_line, y, Cursor_pos)
@@ -132,22 +130,22 @@ function love.update(dt)
       if Lines.current.mode == 'drawing' then
         local drawing = Lines.current
         local x, y = love.mouse.getX(), love.mouse.getY()
-        if y >= drawing.y and y < drawing.y + pixels(drawing.h) and x >= 16 and x < 16+Drawing_width then
+        if y >= drawing.y and y < drawing.y + Drawing.pixels(drawing.h) and x >= 16 and x < 16+Drawing_width then
           if drawing.pending.mode == 'freehand' then
-            table.insert(drawing.pending.points, {x=coord(love.mouse.getX()-16), y=coord(love.mouse.getY()-drawing.y)})
+            table.insert(drawing.pending.points, {x=Drawing.coord(love.mouse.getX()-16), y=Drawing.coord(love.mouse.getY()-drawing.y)})
           elseif drawing.pending.mode == 'move' then
-            local mx,my = coord(x-16), coord(y-drawing.y)
+            local mx,my = Drawing.coord(x-16), Drawing.coord(y-drawing.y)
             drawing.pending.target_point.x = mx
             drawing.pending.target_point.y = my
           end
         end
       end
     end
-  elseif Current_mode == 'move' then
+  elseif Current_drawing_mode == 'move' then
     local drawing = Lines.current
     local x, y = love.mouse.getX(), love.mouse.getY()
-    if y >= drawing.y and y < drawing.y + pixels(drawing.h) and x >= 16 and x < 16+Drawing_width then
-      local mx,my = coord(x-16), coord(y-drawing.y)
+    if y >= drawing.y and y < drawing.y + Drawing.pixels(drawing.h) and x >= 16 and x < 16+Drawing_width then
+      local mx,my = Drawing.coord(x-16), Drawing.coord(y-drawing.y)
       drawing.pending.target_point.x = mx
       drawing.pending.target_point.y = my
     end
@@ -167,18 +165,18 @@ function love.mousepressed(x,y, button)
     elseif line.mode == 'drawing' then
       local drawing = line
       local x, y = love.mouse.getX(), love.mouse.getY()
-      if y >= drawing.y and y < drawing.y + pixels(drawing.h) and x >= 16 and x < 16+Drawing_width then
-        if Current_mode == 'freehand' then
-          drawing.pending = {mode=Current_mode, points={{x=coord(x-16), y=coord(y-drawing.y)}}}
-        elseif Current_mode == 'line' or Current_mode == 'manhattan' then
-          local j = insert_point(drawing.points, coord(x-16), coord(y-drawing.y))
-          drawing.pending = {mode=Current_mode, p1=j}
-        elseif Current_mode == 'polygon' then
-          local j = insert_point(drawing.points, coord(x-16), coord(y-drawing.y))
-          drawing.pending = {mode=Current_mode, vertices={j}}
-        elseif Current_mode == 'circle' then
-          local j = insert_point(drawing.points, coord(x-16), coord(y-drawing.y))
-          drawing.pending = {mode=Current_mode, center=j}
+      if y >= drawing.y and y < drawing.y + Drawing.pixels(drawing.h) and x >= 16 and x < 16+Drawing_width then
+        if Current_drawing_mode == 'freehand' then
+          drawing.pending = {mode=Current_drawing_mode, points={{x=Drawing.coord(x-16), y=Drawing.coord(y-drawing.y)}}}
+        elseif Current_drawing_mode == 'line' or Current_drawing_mode == 'manhattan' then
+          local j = Drawing.insert_point(drawing.points, Drawing.coord(x-16), Drawing.coord(y-drawing.y))
+          drawing.pending = {mode=Current_drawing_mode, p1=j}
+        elseif Current_drawing_mode == 'polygon' then
+          local j = Drawing.insert_point(drawing.points, Drawing.coord(x-16), Drawing.coord(y-drawing.y))
+          drawing.pending = {mode=Current_drawing_mode, vertices={j}}
+        elseif Current_drawing_mode == 'circle' then
+          local j = Drawing.insert_point(drawing.points, Drawing.coord(x-16), Drawing.coord(y-drawing.y))
+          drawing.pending = {mode=Current_drawing_mode, center=j}
         end
         Lines.current = drawing
       end
@@ -187,55 +185,55 @@ function love.mousepressed(x,y, button)
 end
 
 function love.mousereleased(x,y, button)
-  if Current_mode == 'move' then
-    Current_mode = Previous_mode
-    Previous_mode = nil
+  if Current_drawing_mode == 'move' then
+    Current_drawing_mode = Previous_drawing_mode
+    Previous_drawing_mode = nil
   elseif Lines.current then
     if Lines.current.pending then
       if Lines.current.pending.mode == 'freehand' then
         -- the last point added during update is good enough
         table.insert(Lines.current.shapes, Lines.current.pending)
       elseif Lines.current.pending.mode == 'line' then
-        local mx,my = coord(x-16), coord(y-Lines.current.y)
+        local mx,my = Drawing.coord(x-16), Drawing.coord(y-Lines.current.y)
         if mx >= 0 and mx < 256 and my >= 0 and my < Lines.current.h then
-          local j = insert_point(Lines.current.points, mx,my)
+          local j = Drawing.insert_point(Lines.current.points, mx,my)
           Lines.current.pending.p2 = j
           table.insert(Lines.current.shapes, Lines.current.pending)
         end
       elseif Lines.current.pending.mode == 'manhattan' then
         local p1 = Lines.current.points[Lines.current.pending.p1]
-        local mx,my = coord(x-16), coord(y-Lines.current.y)
+        local mx,my = Drawing.coord(x-16), Drawing.coord(y-Lines.current.y)
         if mx >= 0 and mx < 256 and my >= 0 and my < Lines.current.h then
           if math.abs(mx-p1.x) > math.abs(my-p1.y) then
-            local j = insert_point(Lines.current.points, mx, p1.y)
+            local j = Drawing.insert_point(Lines.current.points, mx, p1.y)
             Lines.current.pending.p2 = j
           else
-            local j = insert_point(Lines.current.points, p1.x, my)
+            local j = Drawing.insert_point(Lines.current.points, p1.x, my)
             Lines.current.pending.p2 = j
           end
           local p2 = Lines.current.points[Lines.current.pending.p2]
-          love.mouse.setPosition(16+pixels(p2.x), Lines.current.y+pixels(p2.y))
+          love.mouse.setPosition(16+Drawing.pixels(p2.x), Lines.current.y+Drawing.pixels(p2.y))
           table.insert(Lines.current.shapes, Lines.current.pending)
         end
       elseif Lines.current.pending.mode == 'polygon' then
-        local mx,my = coord(x-16), coord(y-Lines.current.y)
+        local mx,my = Drawing.coord(x-16), Drawing.coord(y-Lines.current.y)
         if mx >= 0 and mx < 256 and my >= 0 and my < Lines.current.h then
-          local j = insert_point(Lines.current.points, mx,my)
+          local j = Drawing.insert_point(Lines.current.points, mx,my)
           table.insert(Lines.current.shapes, Lines.current.pending)
         end
         table.insert(Lines.current.shapes, Lines.current.pending)
       elseif Lines.current.pending.mode == 'circle' then
-        local mx,my = coord(x-16), coord(y-Lines.current.y)
+        local mx,my = Drawing.coord(x-16), Drawing.coord(y-Lines.current.y)
         if mx >= 0 and mx < 256 and my >= 0 and my < Lines.current.h then
           local center = Lines.current.points[Lines.current.pending.center]
           Lines.current.pending.radius = math.dist(center.x,center.y, mx,my)
           table.insert(Lines.current.shapes, Lines.current.pending)
         end
       elseif Lines.current.pending.mode == 'arc' then
-        local mx,my = coord(x-16), coord(y-Lines.current.y)
+        local mx,my = Drawing.coord(x-16), Drawing.coord(y-Lines.current.y)
         if mx >= 0 and mx < 256 and my >= 0 and my < Lines.current.h then
           local center = Lines.current.points[Lines.current.pending.center]
-          Lines.current.pending.end_angle = angle_with_hint(center.x,center.y, mx,my, Lines.current.pending.end_angle)
+          Lines.current.pending.end_angle = geom.angle_with_hint(center.x,center.y, mx,my, Lines.current.pending.end_angle)
           table.insert(Lines.current.shapes, Lines.current.pending)
         end
       end
@@ -248,213 +246,6 @@ function love.mousereleased(x,y, button)
   end
 end
 
-function insert_point(points, x,y)
-  for i,point in ipairs(points) do
-    if near(point, x,y) then
-      return i
-    end
-  end
-  table.insert(points, {x=x, y=y})
-  return #points
-end
-
-function near(point, x,y)
-  local px,py = pixels(x),pixels(y)
-  local cx,cy = pixels(point.x), pixels(point.y)
-  return (cx-px)*(cx-px) + (cy-py)*(cy-py) < 16
-end
-
-function draw_shape(left,top, drawing, shape)
-  if shape.mode == 'freehand' then
-    local prev = nil
-    for _,point in ipairs(shape.points) do
-      if prev then
-        love.graphics.line(pixels(prev.x)+left,pixels(prev.y)+top, pixels(point.x)+left,pixels(point.y)+top)
-      end
-      prev = point
-    end
-  elseif shape.mode == 'line' or shape.mode == 'manhattan' then
-    local p1 = drawing.points[shape.p1]
-    local p2 = drawing.points[shape.p2]
-    love.graphics.line(pixels(p1.x)+left,pixels(p1.y)+top, pixels(p2.x)+left,pixels(p2.y)+top)
-  elseif shape.mode == 'polygon' then
-    local prev = nil
-    for _,point in ipairs(shape.vertices) do
-      local curr = drawing.points[point]
-      if prev then
-        love.graphics.line(pixels(prev.x)+left,pixels(prev.y)+top, pixels(curr.x)+left,pixels(curr.y)+top)
-      end
-      prev = curr
-    end
-    -- close the loop
-    local curr = drawing.points[shape.vertices[1]]
-    love.graphics.line(pixels(prev.x)+left,pixels(prev.y)+top, pixels(curr.x)+left,pixels(curr.y)+top)
-  elseif shape.mode == 'circle' then
-    local center = drawing.points[shape.center]
-    love.graphics.circle('line', pixels(center.x)+left,pixels(center.y)+top, pixels(shape.radius))
-  elseif shape.mode == 'arc' then
-    local center = drawing.points[shape.center]
-    love.graphics.arc('line', 'open', pixels(center.x)+left,pixels(center.y)+top, pixels(shape.radius), shape.start_angle, shape.end_angle, 360)
-  elseif shape.mode == 'deleted' then
-  else
-    print(shape.mode)
-    assert(false)
-  end
-end
-
-function draw_pending_shape(left,top, drawing)
-  local shape = drawing.pending
-  if shape.mode == 'freehand' then
-    draw_shape(left,top, drawing, shape)
-  elseif shape.mode == 'line' then
-    local p1 = drawing.points[shape.p1]
-    local mx,my = coord(love.mouse.getX()-16), coord(love.mouse.getY()-drawing.y)
-    if mx < 0 or mx >= 256 or my < 0 or my >= drawing.h then
-      return
-    end
-    love.graphics.line(pixels(p1.x)+left,pixels(p1.y)+top, pixels(mx)+left,pixels(my)+top)
-  elseif shape.mode == 'manhattan' then
-    local p1 = drawing.points[shape.p1]
-    local mx,my = coord(love.mouse.getX()-16), coord(love.mouse.getY()-drawing.y)
-    if mx < 0 or mx >= 256 or my < 0 or my >= drawing.h then
-      return
-    end
-    if math.abs(mx-p1.x) > math.abs(my-p1.y) then
-      love.graphics.line(pixels(p1.x)+left,pixels(p1.y)+top, pixels(mx)+left,pixels(p1.y)+top)
-    else
-      love.graphics.line(pixels(p1.x)+left,pixels(p1.y)+top, pixels(p1.x)+left,pixels(my)+top)
-    end
-  elseif shape.mode == 'polygon' then
-    -- don't close the loop on a pending polygon
-    local prev = nil
-    for _,point in ipairs(shape.vertices) do
-      local curr = drawing.points[point]
-      if prev then
-        love.graphics.line(pixels(prev.x)+left,pixels(prev.y)+top, pixels(curr.x)+left,pixels(curr.y)+top)
-      end
-      prev = curr
-    end
-    love.graphics.line(pixels(prev.x)+left,pixels(prev.y)+top, love.mouse.getX(),love.mouse.getY())
-  elseif shape.mode == 'circle' then
-    local center = drawing.points[shape.center]
-    local mx,my = coord(love.mouse.getX()-16), coord(love.mouse.getY()-drawing.y)
-    if mx < 0 or mx >= 256 or my < 0 or my >= drawing.h then
-      return
-    end
-    local cx,cy = pixels(center.x)+left, pixels(center.y)+top
-    love.graphics.circle('line', cx,cy, math.dist(cx,cy, love.mouse.getX(),love.mouse.getY()))
-  elseif shape.mode == 'arc' then
-    local center = drawing.points[shape.center]
-    local mx,my = coord(love.mouse.getX()-16), coord(love.mouse.getY()-drawing.y)
-    if mx < 0 or mx >= 256 or my < 0 or my >= drawing.h then
-      return
-    end
-    shape.end_angle = angle_with_hint(center.x,center.y, mx,my, shape.end_angle)
-    local cx,cy = pixels(center.x)+left, pixels(center.y)+top
-    love.graphics.arc('line', 'open', cx,cy, pixels(shape.radius), shape.start_angle, shape.end_angle, 360)
-  end
-end
-
-function on_shape(x,y, drawing, shape)
-  if shape.mode == 'freehand' then
-    return on_freehand(x,y, drawing, shape)
-  elseif shape.mode == 'line' then
-    return on_line(x,y, drawing, shape)
-  elseif shape.mode == 'manhattan' then
-    return x == drawing.points[shape.p1].x or y == drawing.points[shape.p1].y
-  elseif shape.mode == 'polygon' then
-    return on_polygon(x,y, drawing, shape)
-  elseif shape.mode == 'circle' then
-    local center = drawing.points[shape.center]
-    return math.dist(center.x,center.y, x,y) == shape.radius
-  elseif shape.mode == 'arc' then
-    local center = drawing.points[shape.center]
-    local dist = math.dist(center.x,center.y, x,y)
-    if dist < shape.radius*0.95 or dist > shape.radius*1.05 then
-      return false
-    end
-    return angle_between(center.x,center.y, x,y, shape.start_angle,shape.end_angle)
-  elseif shape.mode == 'deleted' then
-  else
-    print(shape.mode)
-    assert(false)
-  end
-end
-
-function on_freehand(x,y, drawing, shape)
-  local prev
-  for _,p in ipairs(shape.points) do
-    if prev then
-      if on_line(x,y, drawing, {p1=prev, p2=p}) then
-        return true
-      end
-    end
-    prev = p
-  end
-  return false
-end
-
-function on_line(x,y, drawing, shape)
-  local p1,p2
-  if type(shape.p1) == 'number' then
-    p1 = drawing.points[shape.p1]
-    p2 = drawing.points[shape.p2]
-  else
-    p1 = shape.p1
-    p2 = shape.p2
-  end
-  if p1.x == p2.x then
-    if math.abs(p1.x-x) > 5 then
-      return false
-    end
-    local y1,y2 = p1.y,p2.y
-    if y1 > y2 then
-      y1,y2 = y2,y1
-    end
-    return y >= y1 and y <= y2
-  end
-  -- has the right slope and intercept
-  local m = (p2.y - p1.y) / (p2.x - p1.x)
-  local yp = p1.y + m*(x-p1.x)
-  if yp < 0.95*y or yp > 1.05*y then
-    return false
-  end
-  -- between endpoints
-  local k = (x-p1.x) / (p2.x-p1.x)
-  return k > -0.05 and k < 1.05
-end
-
-function on_polygon(x,y, drawing, shape)
-  local prev
-  for _,p in ipairs(shape.vertices) do
-    if prev then
-      if on_line(x,y, drawing, {p1=prev, p2=p}) then
-        return true
-      end
-    end
-    prev = p
-  end
-  return on_line(x,y, drawing, {p1=shape.vertices[1], p2=shape.vertices[#shape.vertices]})
-end
-
-function angle_between(x1,y1, x2,y2, s,e)
-  local angle = math.angle(x1,y1, x2,y2)
-  if s > e then
-    s,e = e,s
-  end
-  -- I'm not sure this is right or ideal..
-  angle = angle-math.pi*2
-  if s <= angle and angle <= e then
-    return true
-  end
-  angle = angle+math.pi*2
-  if s <= angle and angle <= e then
-    return true
-  end
-  angle = angle+math.pi*2
-  return s <= angle and angle <= e
-end
-
 function love.textinput(t)
   if love.mouse.isDown('1') then return end
   if Lines[Cursor_line].mode == 'drawing' then return end
@@ -565,17 +356,17 @@ function keychord_pressed(chord)
     Drawing_width = Drawing_width*Zoom
   -- shortcuts for drawings
   elseif chord == 'escape' and love.mouse.isDown('1') then
-    local drawing = current_drawing()
+    local drawing = Drawing.current_drawing()
     drawing.pending = {}
   elseif chord == 'C-f' and not love.mouse.isDown('1') then
-    Current_mode = 'freehand'
+    Current_drawing_mode = 'freehand'
   elseif chord == 'C-g' and not love.mouse.isDown('1') then
-    Current_mode = 'polygon'
+    Current_drawing_mode = 'polygon'
   elseif love.mouse.isDown('1') and chord == 'g' then
-    Current_mode = 'polygon'
-    local drawing = current_drawing()
+    Current_drawing_mode = 'polygon'
+    local drawing = Drawing.current_drawing()
     if drawing.pending.mode == 'freehand' then
-      drawing.pending.vertices = {insert_point(drawing.points, drawing.pending.points[1].x, drawing.pending.points[1].y)}
+      drawing.pending.vertices = {Drawing.insert_point(drawing.points, drawing.pending.points[1].x, drawing.pending.points[1].y)}
     elseif drawing.pending.mode == 'line' or drawing.pending.mode == 'manhattan' then
       if drawing.pending.vertices == nil then
         drawing.pending.vertices = {drawing.pending.p1}
@@ -584,26 +375,26 @@ function keychord_pressed(chord)
       drawing.pending.vertices = {drawing.pending.center}
     end
     drawing.pending.mode = 'polygon'
-  elseif love.mouse.isDown('1') and chord == 'p' and Current_mode == 'polygon' then
-    local drawing = current_drawing()
-    local mx,my = coord(love.mouse.getX()-16), coord(love.mouse.getY()-drawing.y)
-    local j = insert_point(drawing.points, mx,my)
+  elseif love.mouse.isDown('1') and chord == 'p' and Current_drawing_mode == 'polygon' then
+    local drawing = Drawing.current_drawing()
+    local mx,my = Drawing.coord(love.mouse.getX()-16), Drawing.coord(love.mouse.getY()-drawing.y)
+    local j = Drawing.insert_point(drawing.points, mx,my)
     table.insert(drawing.pending.vertices, j)
   elseif chord == 'C-c' and not love.mouse.isDown('1') then
-    Current_mode = 'circle'
-  elseif love.mouse.isDown('1') and chord == 'a' and Current_mode == 'circle' then
-    local drawing = current_drawing()
+    Current_drawing_mode = 'circle'
+  elseif love.mouse.isDown('1') and chord == 'a' and Current_drawing_mode == 'circle' then
+    local drawing = Drawing.current_drawing()
     drawing.pending.mode = 'arc'
-    local mx,my = coord(love.mouse.getX()-16), coord(love.mouse.getY()-drawing.y)
-    local j = insert_point(drawing.points, mx,my)
+    local mx,my = Drawing.coord(love.mouse.getX()-16), Drawing.coord(love.mouse.getY()-drawing.y)
+    local j = Drawing.insert_point(drawing.points, mx,my)
     local center = drawing.points[drawing.pending.center]
     drawing.pending.radius = math.dist(center.x,center.y, mx,my)
-    drawing.pending.start_angle = math.angle(center.x,center.y, mx,my)
+    drawing.pending.start_angle = geom.angle(center.x,center.y, mx,my)
   elseif love.mouse.isDown('1') and chord == 'c' then
-    Current_mode = 'circle'
-    local drawing = current_drawing()
+    Current_drawing_mode = 'circle'
+    local drawing = Drawing.current_drawing()
     if drawing.pending.mode == 'freehand' then
-      drawing.pending.center = insert_point(drawing.points, drawing.pending.points[1].x, drawing.pending.points[1].y)
+      drawing.pending.center = Drawing.insert_point(drawing.points, drawing.pending.points[1].x, drawing.pending.points[1].y)
     elseif drawing.pending.mode == 'line' or drawing.pending.mode == 'manhattan' then
       drawing.pending.center = drawing.pending.p1
     elseif drawing.pending.mode == 'polygon' then
@@ -611,10 +402,10 @@ function keychord_pressed(chord)
     end
     drawing.pending.mode = 'circle'
   elseif love.mouse.isDown('1') and chord == 'l' then
-    Current_mode = 'line'
-    local drawing = current_drawing()
+    Current_drawing_mode = 'line'
+    local drawing = Drawing.current_drawing()
     if drawing.pending.mode == 'freehand' then
-      drawing.pending.p1 = insert_point(drawing.points, drawing.pending.points[1].x, drawing.pending.points[1].y)
+      drawing.pending.p1 = Drawing.insert_point(drawing.points, drawing.pending.points[1].x, drawing.pending.points[1].y)
     elseif drawing.pending.mode == 'circle' or drawing.pending.mode == 'arc' then
       drawing.pending.p1 = drawing.pending.center
     elseif drawing.pending.mode == 'polygon' then
@@ -622,16 +413,16 @@ function keychord_pressed(chord)
     end
     drawing.pending.mode = 'line'
   elseif chord == 'C-l' then
-    Current_mode = 'line'
-    local drawing,_,shape = select_shape_at_mouse()
+    Current_drawing_mode = 'line'
+    local drawing,_,shape = Drawing.select_shape_at_mouse()
     if drawing then
       convert_line(drawing, shape)
     end
   elseif love.mouse.isDown('1') and chord == 'm' then
-    Current_mode = 'manhattan'
-    local drawing = select_drawing_at_mouse()
+    Current_drawing_mode = 'manhattan'
+    local drawing = Drawing.select_drawing_at_mouse()
     if drawing.pending.mode == 'freehand' then
-      drawing.pending.p1 = insert_point(drawing.points, drawing.pending.points[1].x, drawing.pending.points[1].y)
+      drawing.pending.p1 = Drawing.insert_point(drawing.points, drawing.pending.points[1].x, drawing.pending.points[1].y)
     elseif drawing.pending.mode == 'line' then
       -- do nothing
     elseif drawing.pending.mode == 'polygon' then
@@ -641,37 +432,37 @@ function keychord_pressed(chord)
     end
     drawing.pending.mode = 'manhattan'
   elseif chord == 'C-m' and not love.mouse.isDown('1') then
-    Current_mode = 'manhattan'
-    local drawing,_,shape = select_shape_at_mouse()
+    Current_drawing_mode = 'manhattan'
+    local drawing,_,shape = Drawing.select_shape_at_mouse()
     if drawing then
       convert_horvert(drawing, shape)
     end
   elseif chord == 'C-s' and not love.mouse.isDown('1') then
-    local drawing,_,shape = select_shape_at_mouse()
+    local drawing,_,shape = Drawing.select_shape_at_mouse()
     if drawing then
       smoothen(shape)
     end
   elseif chord == 'C-v' and not love.mouse.isDown('1') then
-    local drawing,_,p = select_point_at_mouse()
+    local drawing,_,p = Drawing.select_point_at_mouse()
     if drawing then
-      Previous_mode = Current_mode
-      Current_mode = 'move'
-      drawing.pending = {mode=Current_mode, target_point=p}
+      Previous_drawing_mode = Current_drawing_mode
+      Current_drawing_mode = 'move'
+      drawing.pending = {mode=Current_drawing_mode, target_point=p}
       Lines.current = drawing
     end
   elseif love.mouse.isDown('1') and chord == 'v' then
-    local drawing,_,p = select_point_at_mouse()
+    local drawing,_,p = Drawing.select_point_at_mouse()
     if drawing then
-      Previous_mode = Current_mode
-      Current_mode = 'move'
-      drawing.pending = {mode=Current_mode, target_point=p}
+      Previous_drawing_mode = Current_drawing_mode
+      Current_drawing_mode = 'move'
+      drawing.pending = {mode=Current_drawing_mode, target_point=p}
       Lines.current = drawing
     end
   elseif chord == 'C-d' and not love.mouse.isDown('1') then
-    local drawing,i,p = select_point_at_mouse()
+    local drawing,i,p = Drawing.select_point_at_mouse()
     if drawing then
       for _,shape in ipairs(drawing.shapes) do
-        if contains_point(shape, i) then
+        if Drawing.contains_point(shape, i) then
           if shape.mode == 'polygon' then
             local idx = table.find(shape.vertices, i)
             assert(idx)
@@ -686,12 +477,12 @@ function keychord_pressed(chord)
       end
       drawing.points[i].deleted = true
     end
-    local drawing,_,shape = select_shape_at_mouse()
+    local drawing,_,shape = Drawing.select_shape_at_mouse()
     if drawing then
       shape.mode = 'deleted'
     end
   elseif chord == 'C-h' and not love.mouse.isDown('1') then
-    local drawing = select_drawing_at_mouse()
+    local drawing = Drawing.select_drawing_at_mouse()
     if drawing then
       drawing.show_help = true
     end
@@ -704,123 +495,6 @@ function keychord_pressed(chord)
   end
 end
 
-function current_drawing()
-  local x, y = love.mouse.getX(), love.mouse.getY()
-  for _,drawing in ipairs(Lines) do
-    if drawing.mode == 'drawing' then
-      if y >= drawing.y and y < drawing.y + pixels(drawing.h) and x >= 16 and x < 16+Drawing_width then
-        return drawing
-      end
-    end
-  end
-  return nil
-end
-
-function select_shape_at_mouse()
-  for _,drawing in ipairs(Lines) do
-    if drawing.mode == 'drawing' then
-      local x, y = love.mouse.getX(), love.mouse.getY()
-      if y >= drawing.y and y < drawing.y + pixels(drawing.h) and x >= 16 and x < 16+Drawing_width then
-        local mx,my = coord(love.mouse.getX()-16), coord(love.mouse.getY()-drawing.y)
-        for i,shape in ipairs(drawing.shapes) do
-          assert(shape)
-          if on_shape(mx,my, drawing, shape) then
-            return drawing,i,shape
-          end
-        end
-      end
-    end
-  end
-end
-
-function select_point_at_mouse()
-  for _,drawing in ipairs(Lines) do
-    if drawing.mode == 'drawing' then
-      local x, y = love.mouse.getX(), love.mouse.getY()
-      if y >= drawing.y and y < drawing.y + pixels(drawing.h) and x >= 16 and x < 16+Drawing_width then
-        local mx,my = coord(love.mouse.getX()-16), coord(love.mouse.getY()-drawing.y)
-        for i,point in ipairs(drawing.points) do
-          assert(point)
-          if near(point, mx,my) then
-            return drawing,i,point
-          end
-        end
-      end
-    end
-  end
-end
-
-function select_drawing_at_mouse()
-  for _,drawing in ipairs(Lines) do
-    if drawing.mode == 'drawing' then
-      local x, y = love.mouse.getX(), love.mouse.getY()
-      if y >= drawing.y and y < drawing.y + pixels(drawing.h) and x >= 16 and x < 16+Drawing_width then
-        return drawing
-      end
-    end
-  end
-end
-
-function contains_point(shape, p)
-  if shape.mode == 'freehand' then
-    -- not supported
-  elseif shape.mode == 'line' or shape.mode == 'manhattan' then
-    return shape.p1 == p or shape.p2 == p
-  elseif shape.mode == 'polygon' then
-    return table.find(shape.vertices, p)
-  elseif shape.mode == 'circle' then
-    return shape.center == p
-  elseif shape.mode == 'arc' then
-    return shape.center == p
-    -- ugh, how to support angles
-  elseif shape.mode == 'deleted' then
-    -- already done
-  else
-    print(shape.mode)
-    assert(false)
-  end
-end
-
-function convert_line(drawing, shape)
-  -- Perhaps we should do a more sophisticated "simple linear regression"
-  -- here:
-  --   https://en.wikipedia.org/wiki/Linear_regression#Simple_and_multiple_linear_regression
-  -- But this works well enough for close-to-linear strokes.
-  assert(shape.mode == 'freehand')
-  shape.mode = 'line'
-  shape.p1 = insert_point(drawing.points, shape.points[1].x, shape.points[1].y)
-  local n = #shape.points
-  shape.p2 = insert_point(drawing.points, shape.points[n].x, shape.points[n].y)
-end
-
--- turn a line either horizontal or vertical
-function convert_horvert(drawing, shape)
-  if shape.mode == 'freehand' then
-    convert_line(shape)
-  end
-  assert(shape.mode == 'line')
-  local p1 = drawing.points[shape.p1]
-  local p2 = drawing.points[shape.p2]
-  if math.abs(p1.x-p2.x) > math.abs(p1.y-p2.y) then
-    p2.y = p1.y
-  else
-    p2.x = p1.x
-  end
-end
-
-function smoothen(shape)
-  assert(shape.mode == 'freehand')
-  for _=1,7 do
-    for i=2,#shape.points-1 do
-      local a = shape.points[i-1]
-      local b = shape.points[i]
-      local c = shape.points[i+1]
-      b.x = (a.x + b.x + c.x)/3
-      b.y = (a.y + b.y + c.y)/3
-    end
-  end
-end
-
 function love.keyreleased(key, scancode)
 end
 
@@ -831,281 +505,3 @@ function table.find(h, x)
     end
   end
 end
-
-function angle_with_hint(x1, y1, x2, y2, hint)
-  local result = math.angle(x1,y1, x2,y2)
-  if hint then
-    -- Smooth the discontinuity where angle goes from positive to negative.
-    -- The hint is a memory of which way we drew it last time.
-    while result > hint+math.pi/10 do
-      result = result-math.pi*2
-    end
-    while result < hint-math.pi/10 do
-      result = result+math.pi*2
-    end
-  end
-  return result
-end
-
--- result is from -π/2 to 3π/2, approximately adding math.atan2 from Lua 5.3
--- (LÖVE is Lua 5.1)
-function math.angle(x1,y1, x2,y2)
-  local result = math.atan((y2-y1)/(x2-x1))
-  if x2 < x1 then
-    result = result+math.pi
-  end
-  return result
-end
-
-function math.dist(x1,y1, x2,y2) return ((x2-x1)^2+(y2-y1)^2)^0.5 end
-
-function load_from_disk(filename)
-  local infile = io.open(filename)
-  local result = load_from_file(infile)
-  if infile then infile:close() end
-  return result
-end
-
-function load_from_file(infile)
-  local result = {}
-  if infile then
-    local infile_next_line = infile:lines()  -- works with both Lua files and LÖVE Files (https://www.love2d.org/wiki/File)
-    while true do
-      local line = infile_next_line()
-      if line == nil then break end
-      if line == '```lines' then  -- inflexible with whitespace since these files are always autogenerated
-        table.insert(result, load_drawing(infile_next_line))
-      else
-        table.insert(result, {mode='text', data=line})
-      end
-    end
-  end
-  if #result == 0 then
-    table.insert(result, {mode='text', data=''})
-  end
-  return result
-end
-
-function save_to_disk(lines, filename)
-  local outfile = io.open(filename, 'w')
-  for _,line in ipairs(lines) do
-    if line.mode == 'drawing' then
-      store_drawing(outfile, line)
-    else
-      outfile:write(line.data..'\n')
-    end
-  end
-  outfile:close()
-end
-
-json = require 'json'
-function load_drawing(infile_next_line)
-  local drawing = {mode='drawing', h=256/2, points={}, shapes={}, pending={}}
-  while true do
-    local line = infile_next_line()
-    assert(line)
-    if line == '```' then break end
-    local shape = json.decode(line)
-    if shape.mode == 'line' or shape.mode == 'manhattan' then
-      shape.p1 = insert_point(drawing.points, shape.p1.x, shape.p1.y)
-      shape.p2 = insert_point(drawing.points, shape.p2.x, shape.p2.y)
-    elseif shape.mode == 'polygon' then
-      for i,p in ipairs(shape.vertices) do
-        shape.vertices[i] = insert_point(drawing.points, p.x,p.y)
-      end
-    elseif shape.mode == 'circle' or shape.mode == 'arc' then
-      shape.center = insert_point(drawing.points, shape.center.x,shape.center.y)
-    end
-    table.insert(drawing.shapes, shape)
-  end
-  return drawing
-end
-
-function store_drawing(outfile, drawing)
-  outfile:write('```lines\n')
-  for _,shape in ipairs(drawing.shapes) do
-    if shape.mode == 'freehand' then
-      outfile:write(json.encode(shape)..'\n')
-    elseif shape.mode == 'line' or shape.mode == 'manhattan' then
-      local line = json.encode({mode=shape.mode, p1=drawing.points[shape.p1], p2=drawing.points[shape.p2]})
-      outfile:write(line..'\n')
-    elseif shape.mode == 'polygon' then
-      local obj = {mode=shape.mode, vertices={}}
-      for _,p in ipairs(shape.vertices) do
-        table.insert(obj.vertices, drawing.points[p])
-      end
-      local line = json.encode(obj)
-      outfile:write(line..'\n')
-    elseif shape.mode == 'circle' then
-      outfile:write(json.encode({mode=shape.mode, center=drawing.points[shape.center], radius=shape.radius})..'\n')
-    elseif shape.mode == 'arc' then
-      outfile:write(json.encode({mode=shape.mode, center=drawing.points[shape.center], radius=shape.radius, start_angle=shape.start_angle, end_angle=shape.end_angle})..'\n')
-    end
-  end
-  outfile:write('```\n')
-end
-
-icon = {}
-
-function icon.insert_drawing(x, y)
-  love.graphics.setColor(0.7,0.7,0.7)
-  love.graphics.rectangle('line', x,y, 12,12)
-  love.graphics.line(4,y+6, 16,y+6)
-  love.graphics.line(10,y, 10,y+12)
-  love.graphics.setColor(0, 0, 0)
-end
-
-function icon.freehand(x, y)
-  love.graphics.line(x+4,y+7,x+5,y+5)
-  love.graphics.line(x+5,y+5,x+7,y+4)
-  love.graphics.line(x+7,y+4,x+9,y+3)
-  love.graphics.line(x+9,y+3,x+10,y+5)
-  love.graphics.line(x+10,y+5,x+12,y+6)
-  love.graphics.line(x+12,y+6,x+13,y+8)
-  love.graphics.line(x+13,y+8,x+13,y+10)
-  love.graphics.line(x+13,y+10,x+14,y+12)
-  love.graphics.line(x+14,y+12,x+15,y+14)
-  love.graphics.line(x+15,y+14,x+15,y+16)
-end
-
-function icon.line(x, y)
-  love.graphics.line(x+4,y+2, x+16,y+18)
-end
-
-function icon.manhattan(x, y)
-  love.graphics.line(x+4,y+20, x+4,y+2)
-  love.graphics.line(x+4,y+2, x+10,y+2)
-  love.graphics.line(x+10,y+2, x+10,y+10)
-  love.graphics.line(x+10,y+10, x+18,y+10)
-end
-
-function icon.polygon(x, y)
-  love.graphics.line(x+8,y+2, x+14,y+2)
-  love.graphics.line(x+14,y+2, x+18,y+10)
-  love.graphics.line(x+18,y+10, x+10,y+18)
-  love.graphics.line(x+10,y+18, x+4,y+12)
-  love.graphics.line(x+4,y+12, x+8,y+2)
-end
-
-function icon.circle(x, y)
-  love.graphics.circle('line', x+10,y+10, 8)
-end
-
-function draw_help_without_mouse_pressed(drawing)
-  love.graphics.setColor(0,0.5,0)
-  local y = drawing.y+10
-  love.graphics.print("Things you can do:", 16+30,y, 0, Zoom)
-  y = y+15*Zoom
-  love.graphics.print("* Press the mouse button to start drawing a "..current_shape(), 16+30,y, 0, Zoom)
-  y = y+15*Zoom
-  love.graphics.print("* Hover on a point and press 'ctrl+v' to start moving it,", 16+30,y, 0, Zoom)
-  y = y+15*Zoom
-  love.graphics.print("then press the mouse button to finish", 16+30+bullet_indent(),y, 0, Zoom)
-  y = y+15*Zoom
-  love.graphics.print("* Hover on a point or shape and press 'ctrl+d' to delete it", 16+30,y, 0, Zoom)
-  y = y+15*Zoom
-  y = y+15*Zoom
-  if Current_mode ~= 'freehand' then
-    love.graphics.print("* Press 'ctrl+f' to switch to drawing freehand strokes", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
-  end
-  if Current_mode ~= 'line' then
-    love.graphics.print("* Press 'ctrl+l' to switch to drawing lines", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
-  end
-  if Current_mode ~= 'manhattan' then
-    love.graphics.print("* Press 'ctrl+m' to switch to drawing horizontal/vertical lines", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
-  end
-  if Current_mode ~= 'circle' then
-    love.graphics.print("* Press 'ctrl+c' to switch to drawing circles/arcs", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
-  end
-  if Current_mode ~= 'polygon' then
-    love.graphics.print("* Press 'ctrl+g' to switch to drawing polygons", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
-  end
-  love.graphics.print("* Press 'ctrl+=' or 'ctrl+-' to Zoom in or out", 16+30,y, 0, Zoom)
-  y = y+15*Zoom
-  love.graphics.print("* Press 'ctrl+0' to reset Zoom", 16+30,y, 0, Zoom)
-  y = y+15*Zoom
-  y = y+15*Zoom
-  love.graphics.print("Hit 'esc' now to hide this message", 16+30,y, 0, Zoom)
-  y = y+15*Zoom
-  love.graphics.setColor(0,0.5,0, 0.1)
-  love.graphics.rectangle('fill', 16,drawing.y, Drawing_width, math.max(pixels(drawing.h),y-drawing.y))
-end
-
-function draw_help_with_mouse_pressed(drawing)
-  love.graphics.setColor(0,0.5,0)
-  local y = drawing.y+10
-  love.graphics.print("You're currently drawing a "..current_shape(drawing.pending), 16+30,y, 0, Zoom)
-  y = y+15*Zoom
-  love.graphics.print('Things you can do now:', 16+30,y, 0, Zoom)
-  y = y+15*Zoom
-  if Current_mode == 'freehand' then
-    love.graphics.print('* Release the mouse button to finish drawing the stroke', 16+30,y, 0, Zoom)
-    y = y+15*Zoom
-  elseif Current_mode == 'line' or Current_mode == 'manhattan' then
-    love.graphics.print('* Release the mouse button to finish drawing the line', 16+30,y, 0, Zoom)
-    y = y+15*Zoom
-  elseif Current_mode == 'circle' then
-    if drawing.pending.mode == 'circle' then
-      love.graphics.print('* Release the mouse button to finish drawing the circle', 16+30,y, 0, Zoom)
-      y = y+15*Zoom
-      love.graphics.print("* Press 'a' to draw just an arc of a circle", 16+30,y, 0, Zoom)
-    else
-      love.graphics.print('* Release the mouse button to finish drawing the arc', 16+30,y, 0, Zoom)
-    end
-    y = y+15*Zoom
-  elseif Current_mode == 'polygon' then
-    love.graphics.print('* Release the mouse button to finish drawing the polygon', 16+30,y, 0, Zoom)
-    y = y+15*Zoom
-    love.graphics.print("* Press 'p' to add a vertex to the polygon", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
-  end
-  love.graphics.print("* Press 'esc' then release the mouse button to cancel the current shape", 16+30,y, 0, Zoom)
-  y = y+15*Zoom
-  y = y+15*Zoom
-  if Current_mode ~= 'line' then
-    love.graphics.print("* Press 'l' to switch to drawing lines", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
-  end
-  if Current_mode ~= 'manhattan' then
-    love.graphics.print("* Press 'm' to switch to drawing horizontal/vertical lines", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
-  end
-  if Current_mode ~= 'circle' then
-    love.graphics.print("* Press 'c' to switch to drawing circles/arcs", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
-  end
-  if Current_mode ~= 'polygon' then
-    love.graphics.print("* Press 'g' to switch to drawing polygons", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
-  end
-  love.graphics.setColor(0,0.5,0, 0.1)
-  love.graphics.rectangle('fill', 16,drawing.y, Drawing_width, math.max(pixels(drawing.h),y-drawing.y))
-end
-
-function current_shape(shape)
-  if Current_mode == 'freehand' then
-    return 'freehand stroke'
-  elseif Current_mode == 'line' then
-    return 'straight line'
-  elseif Current_mode == 'manhattan' then
-    return 'horizontal/vertical line'
-  elseif Current_mode == 'circle' and shape and shape.start_angle then
-    return 'arc'
-  else
-    return Current_mode
-  end
-end
-
-_bullet_indent = nil
-function bullet_indent()
-  if _bullet_indent == nil then
-    local text = love.graphics.newText(love.graphics.getFont(), '* ')
-    _bullet_indent = text:getWidth()
-  end
-  return _bullet_indent
-end