autosave slightly less aggressively

It might reduce wear and tear on disk, and losing 3 seconds of data
doesn't feel catastrophic (short of a C-z rampage).

Thanks to the love2d.org community for the suggestion:
  https://love2d.org/forums/viewtopic.php?f=14&t=93173

4 files changed, 72 insertions, 18 deletions

diff --git a/app.lua b/app.lua
index 99cef81..a887588 100644
--- a/app.lua
+++ b/app.lua
@@ -157,6 +157,14 @@ function App.screen.print(msg, x,y)
   end
 end
 
+App.time = 1
+function App.getTime()
+  return App.time
+end
+function App.wait_fake_time(t)
+  App.time = App.time + t
+end
+
 -- LÖVE's Text primitive retains no trace of the string it was created from,
 -- so we'll wrap it for our tests.
 --
@@ -329,10 +337,14 @@ function App.disable_tests()
   -- test methods are disallowed outside tests
   App.screen.init = nil
   App.filesystem = nil
+  App.time = nil
   App.run_after_textinput = nil
   App.run_after_keychord = nil
   App.keypress = nil
   App.keyrelease = nil
+  App.run_after_mouse_click = nil
+  App.run_after_mouse_press = nil
+  App.run_after_mouse_release = nil
   App.fake_key_pressed = nil
   App.fake_key_press = nil
   App.fake_key_release = nil
@@ -346,6 +358,7 @@ function App.disable_tests()
   App.width = function(text) return text:getWidth() end
   App.open_for_reading = function(filename) return io.open(filename, 'r') end
   App.open_for_writing = function(filename) return io.open(filename, 'w') end
+  App.getTime = love.timer.getTime
   App.getClipboardText = love.system.getClipboardText
   App.setClipboardText = love.system.setClipboardText
   App.modifier_down = love.keyboard.isDown
diff --git a/drawing_tests.lua b/drawing_tests.lua
index b8e1953..faf94ce 100644
--- a/drawing_tests.lua
+++ b/drawing_tests.lua
@@ -10,6 +10,12 @@ function test_creating_drawing_saves()
   App.draw()
   -- click on button to create drawing
   App.run_after_mouse_click(8,Margin_top+8, 1)
+  -- file not immediately saved
+  App.update(0.01)
+  check_nil(App.filesystem['foo'], 'F - test_creating_drawing_saves/early')
+  -- wait until save
+  App.wait_fake_time(3.1)
+  App.update(0)
   -- filesystem contains drawing and an empty line of text
   check_eq(App.filesystem['foo'], '```lines\n```\n\n', 'F - test_creating_drawing_saves')
 end
@@ -41,6 +47,9 @@ function test_draw_line()
   check_eq(p1.y, 6, 'F - test_draw_line/p1:y')
   check_eq(p2.x, 35, 'F - test_draw_line/p2:x')
   check_eq(p2.y, 36, 'F - test_draw_line/p2:y')
+  -- wait until save
+  App.wait_fake_time(3.1)
+  App.update(0)
   -- The format on disk isn't perfectly stable. Table fields can be reordered.
   -- So just reload from disk to verify.
   Lines = load_from_disk(Filename)
@@ -382,6 +391,9 @@ function test_name_point()
   App.run_after_keychord('return')
   check_eq(Current_drawing_mode, 'line', 'F - test_name_point/mode:3')
   check_eq(p2.name, 'A', 'F - test_name_point')
+  -- wait until save
+  App.wait_fake_time(3.1)
+  App.update(0)
   -- change is saved
   Lines = load_from_disk(Filename)
   local p2 = Lines[1].points[drawing.shapes[1].p2]
@@ -410,6 +422,9 @@ function test_move_point()
   check_eq(p2.x, 35, 'F - test_move_point/baseline/p2:x')
   check_eq(p2.y, 36, 'F - test_move_point/baseline/p2:y')
   check_nil(p2.name, 'F - test_move_point/baseline/p2:name')
+  -- wait until save
+  App.wait_fake_time(3.1)
+  App.update(0)
   -- line is saved to disk
   Lines = load_from_disk(Filename)
   local drawing = Lines[1]
@@ -433,6 +448,9 @@ function test_move_point()
   App.run_after_mouse_click(Margin_left+26, Margin_top+Drawing_padding_top+44, 1)
   check_eq(Current_drawing_mode, 'line', 'F - test_move_point/mode:3')
   check_eq(drawing.pending, {}, 'F - test_move_point/pending')
+  -- wait until save
+  App.wait_fake_time(3.1)
+  App.update(0)
   -- change is saved
   Lines = load_from_disk(Filename)
   local p2 = Lines[1].points[drawing.shapes[1].p2]
@@ -462,6 +480,9 @@ function test_delete_lines_at_point()
   App.run_after_keychord('C-d')
   check_eq(drawing.shapes[1].mode, 'deleted', 'F - test_delete_lines_at_point/shape:1')
   check_eq(drawing.shapes[2].mode, 'deleted', 'F - test_delete_lines_at_point/shape:2')
+  -- wait for some time
+  App.wait_fake_time(3.1)
+  App.update(0)
   -- deleted points disappear after file is reloaded
   Lines = load_from_disk(Filename)
   check_eq(#Lines[1].shapes, 0, 'F - test_delete_lines_at_point/save')
@@ -586,6 +607,9 @@ function test_undo_name_point()
   local p2 = drawing.points[drawing.shapes[1].p2]
   check_eq(Next_history, 3, 'F - test_undo_name_point/next_history')
   check_eq(p2.name, '', 'F - test_undo_name_point')  -- not quite what it was before, but close enough
+  -- wait until save
+  App.wait_fake_time(3.1)
+  App.update(0)
   -- undo is saved
   Lines = load_from_disk(Filename)
   local p2 = Lines[1].points[drawing.shapes[1].p2]
@@ -632,6 +656,9 @@ function test_undo_move_point()
   check_eq(Next_history, 2, 'F - test_undo_move_point/next_history')
   check_eq(p2.x, 35, 'F - test_undo_move_point/x')
   check_eq(p2.y, 36, 'F - test_undo_move_point/y')
+  -- wait until save
+  App.wait_fake_time(3.1)
+  App.update(0)
   -- undo is saved
   Lines = load_from_disk(Filename)
   local p2 = Lines[1].points[drawing.shapes[1].p2]
@@ -668,6 +695,9 @@ function test_undo_delete_point()
   check_eq(Next_history, 3, 'F - test_undo_move_point/next_history')
   check_eq(drawing.shapes[1].mode, 'line', 'F - test_undo_delete_point/shape:1')
   check_eq(drawing.shapes[2].mode, 'line', 'F - test_undo_delete_point/shape:2')
+  -- wait until save
+  App.wait_fake_time(3.1)
+  App.update(0)
   -- undo is saved
   Lines = load_from_disk(Filename)
   check_eq(#Lines[1].shapes, 2, 'F - test_undo_delete_point/save')
diff --git a/main.lua b/main.lua
index def3ec2..5f4f2d1 100644
--- a/main.lua
+++ b/main.lua
@@ -76,6 +76,7 @@ Drawing_padding_bottom = 10
 Drawing_padding_height = Drawing_padding_top + Drawing_padding_bottom
 
 Filename = love.filesystem.getUserDirectory()..'/lines.txt'
+Next_save = nil
 
 -- undo
 History = {}
@@ -168,7 +169,7 @@ function love.resize(w, h)
   App.screen.width, App.screen.height = w, h
   Line_width = math.min(40*App.width(Em), App.screen.width-50)
   Text.redraw_all()
-  Last_resize_time = love.timer.getTime()
+  Last_resize_time = App.getTime()
 end
 
 function initialize_font_settings(font_height)
@@ -208,7 +209,7 @@ function App.draw()
 
   -- some hysteresis while resizing
   if Last_resize_time then
-    if love.timer.getTime() - Last_resize_time < 0.1 then
+    if App.getTime() - Last_resize_time < 0.1 then
       return
     else
       Last_resize_time = nil
@@ -235,7 +236,7 @@ function App.draw()
                        if Cursor1.line >= line_index then
                          Cursor1.line = Cursor1.line+1
                        end
-                       save_to_disk(Lines, Filename)
+                       schedule_save()
                        record_undo_event({before=Drawing.before, after=snapshot(line_index-1, line_index+1)})
                      end})
           if Search_term == nil then
@@ -272,13 +273,23 @@ function App.update(dt)
   Cursor_time = Cursor_time + dt
   -- some hysteresis while resizing
   if Last_resize_time then
-    if love.timer.getTime() - Last_resize_time < 0.1 then
+    if App.getTime() - Last_resize_time < 0.1 then
       return
     else
       Last_resize_time = nil
     end
   end
   Drawing.update(dt)
+  if Next_save and Next_save < App.getTime() then
+    save_to_disk(Lines, Filename)
+    Next_save = nil
+  end
+end
+
+function schedule_save()
+  if Next_save == nil then
+    Next_save = App.getTime() + 3  -- short enough that you're likely to still remember what you did
+  end
 end
 
 function App.mousepressed(x,y, mouse_button)
@@ -317,7 +328,7 @@ function App.mousereleased(x,y, button)
   if Search_term then return end
   if Lines.current_drawing then
     Drawing.mouse_released(x,y, button)
-    save_to_disk(Lines, Filename)
+    schedule_save()
     if Drawing.before then
       record_undo_event({before=Drawing.before, after=snapshot(Lines.current_drawing_index)})
       Drawing.before = nil
@@ -358,7 +369,7 @@ function App.textinput(t)
   else
     Text.textinput(t)
   end
-  save_to_disk(Lines, Filename)
+  schedule_save()
 end
 
 function App.keychord_pressed(chord)
@@ -409,7 +420,7 @@ function App.keychord_pressed(chord)
       Selection1 = deepcopy(src.selection)
       patch(Lines, event.after, event.before)
       Text.redraw_all()  -- if we're scrolling, reclaim all fragments to avoid memory leaks
-      save_to_disk(Lines, Filename)
+      schedule_save()
     end
   elseif chord == 'C-y' then
     for _,line in ipairs(Lines) do line.y = nil end  -- just in case we scroll
@@ -421,7 +432,7 @@ function App.keychord_pressed(chord)
       Selection1 = deepcopy(src.selection)
       patch(Lines, event.before, event.after)
       Text.redraw_all()  -- if we're scrolling, reclaim all fragments to avoid memory leaks
-      save_to_disk(Lines, Filename)
+      schedule_save()
     end
   -- clipboard
   elseif chord == 'C-c' then
@@ -436,7 +447,7 @@ function App.keychord_pressed(chord)
     if s then
       App.setClipboardText(s)
     end
-    save_to_disk(Lines, Filename)
+    schedule_save()
   elseif chord == 'C-v' then
     for _,line in ipairs(Lines) do line.y = nil end  -- just in case we scroll
     -- We don't have a good sense of when to scroll, so we'll be conservative
@@ -456,7 +467,7 @@ function App.keychord_pressed(chord)
     if Cursor_y >= App.screen.height - Line_height then
       Text.snap_cursor_to_bottom_of_screen()
     end
-    save_to_disk(Lines, Filename)
+    schedule_save()
     record_undo_event({before=before, after=snapshot(before_line, Cursor1.line)})
   -- dispatch to drawing or text
   elseif App.mouse_down(1) or chord:sub(1,2) == 'C-' then
@@ -466,7 +477,7 @@ function App.keychord_pressed(chord)
       local before = snapshot(drawing_index)
       Drawing.keychord_pressed(chord)
       record_undo_event({before=before, after=snapshot(drawing_index)})
-      save_to_disk(Lines, Filename)
+      schedule_save()
     end
   elseif chord == 'escape' and App.mouse_down(1) then
     local _,drawing = Drawing.current_drawing()
@@ -496,7 +507,7 @@ function App.keychord_pressed(chord)
       end
       record_undo_event({before=before, after=snapshot(Lines.current_drawing_index)})
     end
-    save_to_disk(Lines, Filename)
+    schedule_save()
   else
     for _,line in ipairs(Lines) do line.y = nil end  -- just in case we scroll
     Text.keychord_pressed(chord)
diff --git a/text.lua b/text.lua
index 1ab6303..143a9d0 100644
--- a/text.lua
+++ b/text.lua
@@ -182,7 +182,7 @@ function Text.keychord_pressed(chord)
     if (Cursor_y + Line_height) > App.screen.height then
       Text.snap_cursor_to_bottom_of_screen()
     end
-    save_to_disk(Lines, Filename)
+    schedule_save()
     record_undo_event({before=before, after=snapshot(before_line, Cursor1.line)})
   elseif chord == 'tab' then
     local before = snapshot(Cursor1.line)
@@ -193,12 +193,12 @@ function Text.keychord_pressed(chord)
       Text.snap_cursor_to_bottom_of_screen()
 --?       print('=>', Screen_top1.line, Screen_top1.pos, Cursor1.line, Cursor1.pos, Screen_bottom1.line, Screen_bottom1.pos)
     end
-    save_to_disk(Lines, Filename)
+    schedule_save()
     record_undo_event({before=before, after=snapshot(Cursor1.line)})
   elseif chord == 'backspace' then
     if Selection1.line then
       Text.delete_selection()
-      save_to_disk(Lines, Filename)
+      schedule_save()
       return
     end
     local before
@@ -235,12 +235,12 @@ function Text.keychord_pressed(chord)
       Text.redraw_all()  -- if we're scrolling, reclaim all fragments to avoid memory leaks
     end
     assert(Text.le1(Screen_top1, Cursor1))
-    save_to_disk(Lines, Filename)
+    schedule_save()
     record_undo_event({before=before, after=snapshot(Cursor1.line)})
   elseif chord == 'delete' then
     if Selection1.line then
       Text.delete_selection()
-      save_to_disk(Lines, Filename)
+      schedule_save()
       return
     end
     local before
@@ -271,7 +271,7 @@ function Text.keychord_pressed(chord)
         table.remove(Lines, Cursor1.line+1)
       end
     end
-    save_to_disk(Lines, Filename)
+    schedule_save()
     record_undo_event({before=before, after=snapshot(Cursor1.line)})
   --== shortcuts that move the cursor
   elseif chord == 'left' then