start sketching out a scrollbar

Not quite ideal: the scrollbar computation only considers
screen_bottom1.line and not screen_bottom1.pos, and so it always assumes
the final line is at the bottom of the screen.

I'm making a deeper change here that I might come to regret. I want to
avoid creating new book-keeping for editor mutations, so I'm putting the
work of computing scrollbar data into clear_screen_line_cache. But that
implies the editor should never clear before updating data, and I caught
one place that wasn't true before. A better name helps avoid this in
future. Let's see how much toil this causes in resolving conflicts.

0012-on.draw

@@ -3,6 +3,7 @@ on.draw = function()
 	draw_editor_border()
 --	love.graphics.rectangle('line', 100-5-Line_number_padding,100-5, 300+Line_number_padding+10, 200+10, 5,5)
 	edit.draw(Editor_state)
+	draw_scrollbar(Editor_state)
 	draw_output_border()
 	draw_menu()
 end

0013-on.keychord_press

@@ -8,4 +8,4 @@ on.keychord_press = function(chord, key)
 	else
 		edit.keychord_press(Editor_state, chord, key)
 	end
-end
+end

0034-draw_scrollbar

@@ -0,0 +1,11 @@
+draw_scrollbar = function(Editor_state)
+	App.color(Normal_color)
+	love.graphics.line(Editor_state.right+30, Editor_state.top, Editor_state.right+30, Editor_state.bottom)
+	love.graphics.line(Editor_state.right+25, Editor_state.top, Editor_state.right+35, Editor_state.top)
+	love.graphics.line(Editor_state.right+25, Editor_state.bottom, Editor_state.right+35, Editor_state.bottom)
+	local sbtop, sbbot = compute_scrollbar(Editor_state)
+	local topy = Editor_state.top + sbtop*(Editor_state.bottom - Editor_state.top)
+	local boty = Editor_state.top +sbbot*(Editor_state.bottom - Editor_state.top)
+	App.color{r=0.6, g=0.6, b=0.8, a=0.5}
+	love.graphics.rectangle('fill', Editor_state.right+20, topy, 20, boty-topy)
+end

0035-compute_scrollbar

@@ -0,0 +1,8 @@
+-- returns:
+-- 	* a float between 0 and 1 regarding the relative position of the top line on screen
+--     * a float between 0 and 1 regarding the relative position of the bottom line on screen
+compute_scrollbar = function(state)
+	local top = state.line_cache[state.screen_top1.line].start_screen_line_index
+	local bot = state.line_cache[state.screen_bottom1.line].start_screen_line_index
+	return (top-1)/state.screen_line_count, bot/state.screen_line_count
+end

Manual_tests.md

@@ -13,6 +13,9 @@ Initializing settings:
     - where exactly the cursor is drawn to highlight a given character
     - analogously, how a shape precisely looks as you draw it
 
+* Type out a wrapping line, select all using ctrl+a and delete. Editor does
+  not crash.
+
 ### Protocol with driver; error-handling
 
 * clone this repo to a new client app, clear its save dir[1], run it, run the

edit.lua

@@ -29,6 +29,7 @@ function edit.initialize_state(top, bottom, left, right, font_height, line_heigh
     --   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
+    --   start_screen_line_index: a count of the number of screen lines above this line
     line_cache = {},
 
     -- Given wrapping, any potential location for the text cursor can be described in two ways:

select.lua

@@ -117,12 +117,12 @@ function Text.delete_selection_without_undo(State)
   end
   State.selection1 = {}
   -- delete everything between min (inclusive) and max (exclusive)
-  Text.clear_screen_line_cache(State, minl)
   local min_offset = Text.offset(State.lines[minl].data, minp)
   local max_offset = Text.offset(State.lines[maxl].data, maxp)
   if minl == maxl then
 --?     print('minl == maxl')
     State.lines[minl].data = State.lines[minl].data:sub(1, min_offset-1)..State.lines[minl].data:sub(max_offset)
+    Text.refresh_screen_line_cache(State, minl)
     return
   end
   assert(minl < maxl)
@@ -132,6 +132,7 @@ function Text.delete_selection_without_undo(State)
     table.remove(State.line_cache, i)
   end
   State.lines[minl].data = State.lines[minl].data:sub(1, min_offset-1)..rhs
+  Text.refresh_screen_line_cache(State, minl)
 end
 
 function Text.selection(State)

text.lua

@@ -28,6 +28,7 @@ function Text.draw(State, line_index, y, startpos, fg, hide_cursor)
       -- render nothing
     else
       final_screen_line_starting_pos = pos
+--?       print(i)
       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)
@@ -166,7 +167,7 @@ end
 function Text.insert_at_cursor(State, t)
   local byte_offset = Text.offset(State.lines[State.cursor1.line].data, State.cursor1.pos)
   State.lines[State.cursor1.line].data = string.sub(State.lines[State.cursor1.line].data, 1, byte_offset-1)..t..string.sub(State.lines[State.cursor1.line].data, byte_offset)
-  Text.clear_screen_line_cache(State, State.cursor1.line)
+  Text.refresh_screen_line_cache(State, State.cursor1.line)
   State.cursor1.pos = State.cursor1.pos+1
 end
 
@@ -235,7 +236,7 @@ function Text.keychord_press(State, chord, readonly)
       }
       Text.redraw_all(State)  -- if we're scrolling, reclaim all fragments to avoid memory leaks
     end
-    Text.clear_screen_line_cache(State, State.cursor1.line)
+    Text.refresh_screen_line_cache(State, State.cursor1.line)
     assert(Text.le1(State.screen_top1, State.cursor1))
     schedule_save(State)
     record_undo_event(State, {before=before, after=snapshot(State, State.cursor1.line)})
@@ -268,7 +269,7 @@ function Text.keychord_press(State, chord, readonly)
       table.remove(State.lines, State.cursor1.line+1)
       table.remove(State.line_cache, State.cursor1.line+1)
     end
-    Text.clear_screen_line_cache(State, State.cursor1.line)
+    Text.refresh_screen_line_cache(State, State.cursor1.line)
     schedule_save(State)
     record_undo_event(State, {before=before, after=snapshot(State, State.cursor1.line)})
   end
@@ -363,7 +364,7 @@ function Text.insert_return(State)
   table.insert(State.lines, State.cursor1.line+1, {data=string.sub(State.lines[State.cursor1.line].data, byte_offset)})
   table.insert(State.line_cache, State.cursor1.line+1, {})
   State.lines[State.cursor1.line].data = string.sub(State.lines[State.cursor1.line].data, 1, byte_offset-1)
-  Text.clear_screen_line_cache(State, State.cursor1.line)
+  Text.refresh_screen_line_cache(State, State.cursor1.line)
   State.cursor1 = {line=State.cursor1.line+1, pos=1}
 end
 
@@ -929,13 +930,42 @@ end
 function Text.redraw_all(State)
 --?   print('clearing fragments')
   State.line_cache = {}
+  local curr_screen_line_index = 1
   for i=1,#State.lines do
     State.line_cache[i] = {}
+    State.line_cache[i].start_screen_line_index = curr_screen_line_index
+    Text.populate_screen_line_starting_pos(State, i)
+    curr_screen_line_index = curr_screen_line_index + #State.line_cache[i].screen_line_starting_pos
   end
+  State.screen_line_count = curr_screen_line_index-1
 end
 
-function Text.clear_screen_line_cache(State, line_index)
+function Text.refresh_scrollbar_data(State)
+--?   print('clearing fragments')
+  local curr_screen_line_index = 1
+  local npopulated = 0
+  for i=1,#State.lines do
+    if State.line_cache[i] == nil then
+      State.line_cache[i] = {}
+    end
+    if State.line_cache[i].screen_line_starting_pos == nil then
+--?       print(('refresh_scrollbar_data: populating line %d'):format(i))
+      Text.populate_screen_line_starting_pos(State, i)
+      npopulated = npopulated+1
+    end
+    State.line_cache[i].start_screen_line_index = curr_screen_line_index
+    curr_screen_line_index = curr_screen_line_index + #State.line_cache[i].screen_line_starting_pos
+  end
+  if npopulated > 1 then
+    print(('refresh_scrollbar_data: had to populate %d lines'):format(npopulated))
+  end
+  State.screen_line_count = curr_screen_line_index-1
+end
+
+function Text.refresh_screen_line_cache(State, line_index)
   State.line_cache[line_index].screen_line_starting_pos = nil
+  Text.populate_screen_line_starting_pos(State, line_index)
+  Text.refresh_scrollbar_data(State)
 end
 
 function trim(s)