bugfix: scrolling in left/right movements

I'd always had a funny feeling there was something missing there but
somehow never thought of the right failing test.

2 files changed, 148 insertions, 10 deletions

diff --git a/text.lua b/text.lua
index 383d762..6fd47cd 100644
--- a/text.lua
+++ b/text.lua
@@ -294,21 +294,21 @@ function Text.keychord_pressed(chord)
     end
     Text.word_right()
   elseif chord == 'home' then
-    Cursor1.pos = 1
+    Text.start_of_line()
     Selection1 = {}
   elseif chord == 'end' then
-    Cursor1.pos = utf8.len(Lines[Cursor1.line].data) + 1
+    Text.end_of_line()
     Selection1 = {}
   elseif chord == 'S-home' then
     if Selection1.line == nil then
       Selection1 = {line=Cursor1.line, pos=Cursor1.pos}
     end
-    Cursor1.pos = 1
+    Text.start_of_line()
   elseif chord == 'S-end' then
     if Selection1.line == nil then
       Selection1 = {line=Cursor1.line, pos=Cursor1.pos}
     end
-    Cursor1.pos = utf8.len(Lines[Cursor1.line].data) + 1
+    Text.end_of_line()
   elseif chord == 'up' then
     Text.up()
     Selection1 = {}
@@ -499,6 +499,22 @@ function Text.down()
 --?   print('=>', Cursor1.line, Cursor1.pos, Screen_top1.line, Screen_top1.pos, Screen_bottom1.line, Screen_bottom1.pos)
 end
 
+function Text.start_of_line()
+  Cursor1.pos = 1
+  if Text.lt1(Cursor1, Screen_top1) then
+    Screen_top1 = {line=Cursor1.line, pos=Cursor1.pos}  -- copy
+  end
+end
+
+function Text.end_of_line()
+  Cursor1.pos = utf8.len(Lines[Cursor1.line].data) + 1
+  local _,botpos = Text.pos_at_start_of_cursor_screen_line()
+  local botline1 = {line=Cursor1.line, pos=botpos}
+  if Text.lt1(Screen_bottom1, botline1) then
+    Text.snap_cursor_to_bottom_of_screen()
+  end
+end
+
 function Text.word_left()
   while true do
     Text.left()
@@ -537,9 +553,11 @@ function Text.left()
         break
       end
     end
-    if Cursor1.line < Screen_top1.line then
-      Screen_top1.line = Cursor1.line
-    end
+  end
+  if Text.lt1(Cursor1, Screen_top1) then
+    local top2 = Text.to2(Screen_top1)
+    top2 = Text.previous_screen_line(top2)
+    Screen_top1 = Text.to1(top2)
   end
 end
 
@@ -557,9 +575,11 @@ function Text.right()
         break
       end
     end
-    if Cursor1.line > Screen_bottom1.line then
-      Screen_top1.line = Cursor1.line
-    end
+  end
+  local _,botpos = Text.pos_at_start_of_cursor_screen_line()
+  local botline1 = {line=Cursor1.line, pos=botpos}
+  if Text.lt1(Screen_bottom1, botline1) then
+    Text.snap_cursor_to_bottom_of_screen()
   end
 end
 
diff --git a/text_tests.lua b/text_tests.lua
index 698c186..3fcb5aa 100644
--- a/text_tests.lua
+++ b/text_tests.lua
@@ -1152,6 +1152,124 @@ function test_typing_on_bottom_line_scrolls_down()
   App.screen.check(y, 'l', 'F - test_typing_on_bottom_line_scrolls_down/screen:3')
 end
 
+function test_left_arrow_scrolls_up_in_wrapped_line()
+  io.write('\ntest_left_arrow_scrolls_up_in_wrapped_line')
+  -- display lines starting from second screen line of a line
+  App.screen.init{width=Margin_left+30, height=60}
+  Lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
+  Line_width = App.screen.width
+  Screen_top1 = {line=3, pos=5}
+  Screen_bottom1 = {}
+  -- cursor is at top of screen
+  Cursor1 = {line=3, pos=5}
+  App.draw()
+  local y = Margin_top
+  App.screen.check(y, 'jkl', 'F - test_left_arrow_scrolls_up_in_wrapped_line/baseline/screen:1')
+  y = y + Line_height
+  App.screen.check(y, 'mno', 'F - test_left_arrow_scrolls_up_in_wrapped_line/baseline/screen:2')
+  -- after hitting the left arrow the screen scrolls up to first screen line
+  App.run_after_keychord('left')
+  y = Margin_top
+  App.screen.check(y, 'ghi ', 'F - test_left_arrow_scrolls_up_in_wrapped_line/screen:1')
+  y = y + Line_height
+  App.screen.check(y, 'jkl', 'F - test_left_arrow_scrolls_up_in_wrapped_line/screen:2')
+  y = y + Line_height
+  App.screen.check(y, 'mno', 'F - test_left_arrow_scrolls_up_in_wrapped_line/screen:3')
+  check_eq(Screen_top1.line, 3, 'F - test_left_arrow_scrolls_up_in_wrapped_line/screen_top')
+  check_eq(Screen_top1.pos, 1, 'F - test_left_arrow_scrolls_up_in_wrapped_line/screen_top')
+  check_eq(Cursor1.line, 3, 'F - test_left_arrow_scrolls_up_in_wrapped_line/cursor:line')
+  check_eq(Cursor1.pos, 4, 'F - test_left_arrow_scrolls_up_in_wrapped_line/cursor:pos')
+end
+
+function test_right_arrow_scrolls_down_in_wrapped_line()
+  io.write('\ntest_right_arrow_scrolls_down_in_wrapped_line')
+  -- display the first three lines with the cursor on the bottom line
+  App.screen.init{width=Margin_left+30, height=60}
+  Lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
+  Line_width = App.screen.width
+  Screen_top1 = {line=1, pos=1}
+  Screen_bottom1 = {}
+  -- cursor is at bottom right of screen
+  Cursor1 = {line=3, pos=5}
+  App.draw()
+  local y = Margin_top
+  App.screen.check(y, 'abc', 'F - test_right_arrow_scrolls_down_in_wrapped_line/baseline/screen:1')
+  y = y + Line_height
+  App.screen.check(y, 'def', 'F - test_right_arrow_scrolls_down_in_wrapped_line/baseline/screen:2')
+  y = y + Line_height
+  App.screen.check(y, 'ghi ', 'F - test_right_arrow_scrolls_down_in_wrapped_line/baseline/screen:3')  -- line wrapping includes trailing whitespace
+  -- after hitting the right arrow the screen scrolls down by one line
+  App.run_after_keychord('right')
+  check_eq(Screen_top1.line, 2, 'F - test_right_arrow_scrolls_down_in_wrapped_line/screen_top')
+  check_eq(Cursor1.line, 3, 'F - test_right_arrow_scrolls_down_in_wrapped_line/cursor:line')
+  check_eq(Cursor1.pos, 6, 'F - test_right_arrow_scrolls_down_in_wrapped_line/cursor:pos')
+  y = Margin_top
+  App.screen.check(y, 'def', 'F - test_right_arrow_scrolls_down_in_wrapped_line/screen:1')
+  y = y + Line_height
+  App.screen.check(y, 'ghi ', 'F - test_right_arrow_scrolls_down_in_wrapped_line/screen:2')
+  y = y + Line_height
+  App.screen.check(y, 'jkl', 'F - test_right_arrow_scrolls_down_in_wrapped_line/screen:3')
+end
+
+function test_home_scrolls_up_in_wrapped_line()
+  io.write('\ntest_home_scrolls_up_in_wrapped_line')
+  -- display lines starting from second screen line of a line
+  App.screen.init{width=Margin_left+30, height=60}
+  Lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
+  Line_width = App.screen.width
+  Screen_top1 = {line=3, pos=5}
+  Screen_bottom1 = {}
+  -- cursor is at top of screen
+  Cursor1 = {line=3, pos=5}
+  App.draw()
+  local y = Margin_top
+  App.screen.check(y, 'jkl', 'F - test_home_scrolls_up_in_wrapped_line/baseline/screen:1')
+  y = y + Line_height
+  App.screen.check(y, 'mno', 'F - test_home_scrolls_up_in_wrapped_line/baseline/screen:2')
+  -- after hitting home the screen scrolls up to first screen line
+  App.run_after_keychord('home')
+  y = Margin_top
+  App.screen.check(y, 'ghi ', 'F - test_home_scrolls_up_in_wrapped_line/screen:1')
+  y = y + Line_height
+  App.screen.check(y, 'jkl', 'F - test_home_scrolls_up_in_wrapped_line/screen:2')
+  y = y + Line_height
+  App.screen.check(y, 'mno', 'F - test_home_scrolls_up_in_wrapped_line/screen:3')
+  check_eq(Screen_top1.line, 3, 'F - test_home_scrolls_up_in_wrapped_line/screen_top')
+  check_eq(Screen_top1.pos, 1, 'F - test_home_scrolls_up_in_wrapped_line/screen_top')
+  check_eq(Cursor1.line, 3, 'F - test_home_scrolls_up_in_wrapped_line/cursor:line')
+  check_eq(Cursor1.pos, 1, 'F - test_home_scrolls_up_in_wrapped_line/cursor:pos')
+end
+
+function test_end_scrolls_down_in_wrapped_line()
+  io.write('\ntest_end_scrolls_down_in_wrapped_line')
+  -- display the first three lines with the cursor on the bottom line
+  App.screen.init{width=Margin_left+30, height=60}
+  Lines = load_array{'abc', 'def', 'ghi jkl', 'mno'}
+  Line_width = App.screen.width
+  Screen_top1 = {line=1, pos=1}
+  Screen_bottom1 = {}
+  -- cursor is at bottom right of screen
+  Cursor1 = {line=3, pos=5}
+  App.draw()
+  local y = Margin_top
+  App.screen.check(y, 'abc', 'F - test_end_scrolls_down_in_wrapped_line/baseline/screen:1')
+  y = y + Line_height
+  App.screen.check(y, 'def', 'F - test_end_scrolls_down_in_wrapped_line/baseline/screen:2')
+  y = y + Line_height
+  App.screen.check(y, 'ghi ', 'F - test_end_scrolls_down_in_wrapped_line/baseline/screen:3')  -- line wrapping includes trailing whitespace
+  -- after hitting end the screen scrolls down by one line
+  App.run_after_keychord('end')
+  check_eq(Screen_top1.line, 2, 'F - test_end_scrolls_down_in_wrapped_line/screen_top')
+  check_eq(Cursor1.line, 3, 'F - test_end_scrolls_down_in_wrapped_line/cursor:line')
+  check_eq(Cursor1.pos, 8, 'F - test_end_scrolls_down_in_wrapped_line/cursor:pos')
+  y = Margin_top
+  App.screen.check(y, 'def', 'F - test_end_scrolls_down_in_wrapped_line/screen:1')
+  y = y + Line_height
+  App.screen.check(y, 'ghi ', 'F - test_end_scrolls_down_in_wrapped_line/screen:2')
+  y = y + Line_height
+  App.screen.check(y, 'jkl', 'F - test_end_scrolls_down_in_wrapped_line/screen:3')
+end
+
 function test_position_cursor_on_recently_edited_wrapping_line()
   -- draw a line wrapping over 2 screen lines
   io.write('\ntest_position_cursor_on_recently_edited_wrapping_line')