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sokoban.love
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UI improvement: more stable scrollbar movement 

scenario: just tap somewhere on a scrollbar.

There should be no scrolling. But before this commit there would be.
This made the scrollbars feel unstable.

I finally figured this out while noodling over a follow-up question to
the previous commit:

  Why was dragging the scrollbar down ever leaving a trail of more than
  just the top line's `starty`? In other words, why was my example:

    line 1: 30
    line 2: 60
    line 3: 90
    line 4: 30
    line 5: 30
    line 6: 30
    ...

  ..and not:

    line 1: 30
    line 2: 30
    line 3: 30
    line 4: 30
    line 5: 30
    line 6: 30
    ...

  ??

The answer: when I grab a scrollbar it always used to jump down!

Usability issues can either exacerbate bugs or make them harder to
diagnose. If I'd implemented scrollbars like this from the start, we'd
either never have noticed the problem of the previous commit or fixed it
much more quickly.
This commit is contained in:
Kartik K. Agaram 2023-12-02 17:22:44 -08:00
parent 793f0daf44
commit 10efcfef8a
3 changed files with 8 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
0016-on.mouse_press
View File

@ -23,6 +23,8 @@ on.mouse_press = function(x,y, mouse_button)
if Show_code then
if on_editor_scrollbar(Current_pane.editor_state, x,y) then
Current_pane.editor_state.scrollbar_drag = true
local sbtop = compute_scrollbar(Current_pane.editor_state)
Current_pane.editor_state.scrollbar_offset = y - sbtop
elseif on_editor_scrollbar_area(Current_pane.editor_state, x,y) then
-- nothing
elseif x < Current_pane.editor_state.right + 15 - 5 and y < Current_pane.editor_state.bottom + 5 + 10 - 5 then
@ -30,6 +32,8 @@ on.mouse_press = function(x,y, mouse_button)
edit.mouse_press(Current_pane.editor_state, x,y, mouse_button)
elseif on_editor_scrollbar(Current_pane.output_editor_state, x,y) then
Current_pane.output_editor_state.scrollbar_drag = true
local sbtop = compute_scrollbar(Current_pane.output_editor_state)
Current_pane.output_editor_state.scrollbar_offset = y - sbtop
elseif on_editor_scrollbar_area(Current_pane.output_editor_state, x,y) then
-- nothing
end
@ -38,4 +42,4 @@ on.mouse_press = function(x,y, mouse_button)
if car.mouse_press then car.mouse_press(x,y, mouse_button) end
if car.mousepressed then car.mousepressed(x,y, mouse_button) end
end
end
end

2
0017-on.mouse_release
View File

@ -14,6 +14,7 @@ on.mouse_release = function(x,y, mouse_button)
if Current_pane.editor_state.scrollbar_drag then
adjust_scrollbar(Current_pane.editor_state, y)
Current_pane.editor_state.scrollbar_drag = nil
Current_pane.editor_state.scrollbar_offset = nil
elseif on_editor_scrollbar_area(Current_pane.editor_state, x,y) then
adjust_scrollbar(Current_pane.editor_state, y)
elseif x < Current_pane.editor_state.right + 15 - 5 and y < Current_pane.editor_state.bottom + 5 + 10 - 5 then
@ -21,6 +22,7 @@ on.mouse_release = function(x,y, mouse_button)
elseif Current_pane.output_editor_state.scrollbar_drag then
adjust_scrollbar(Current_pane.output_editor_state, y)
Current_pane.output_editor_state.scrollbar_drag = nil
Current_pane.output_editor_state.scrollbar_offset = nil
elseif on_editor_scrollbar_area(Current_pane.output_editor_state, x,y) then
adjust_scrollbar(Current_pane.output_editor_state, y)
end

2
0036-adjust_scrollbar
View File

@ -1,5 +1,5 @@
adjust_scrollbar = function(state, y)
local s = (y-state.top) / (state.bottom-state.top)
local s = (y-state.scrollbar_offset-state.top) / (state.bottom-state.top)
local screen_line = s*state.screen_line_count
local line = 1
for i=1,#state.lines do