Merge upstream into main

text.lua

@@ -18,7 +18,7 @@ function Text.draw(State, line_index, y, startpos)
   -- wrap long lines
   local x = State.left
   local pos = 1
-  local screen_line_starting_pos = 1
+  local screen_line_starting_pos = State.screen_top1.pos
   if line_cache.fragments == nil then
     Text.compute_fragments(State, line_index)
   end
@@ -209,8 +209,12 @@ function Text.keychord_pressed(State, chord)
       end
       State.cursor1.line = State.cursor1.line-1
     end
-    if Text.lt1(State.cursor1, State.screen_top1) then
-      local top2 = Text.to2(State, State.screen_top1, State.left, State.right)
+    if State.screen_top1.line > #State.lines then
+      Text.populate_screen_line_starting_pos(State, #State.lines)
+      local line_cache = State.line_cache[#State.line_cache]
+      State.screen_top1 = {line=#State.lines, pos=line_cache.screen_line_starting_pos[#line_cache.screen_line_starting_pos]}
+    elseif Text.lt1(State.cursor1, State.screen_top1) then
+      local top2 = Text.to2(State, State.screen_top1)
       top2 = Text.previous_screen_line(State, top2, State.left, State.right)
       State.screen_top1 = Text.to1(State, top2)
       Text.redraw_all(State)  -- if we're scrolling, reclaim all fragments to avoid memory leaks

text_tests.lua

@@ -42,6 +42,22 @@ function test_backspace_to_delete_drawing()
   check_eq(Editor_state.cursor1.line, 1, 'F - test_backspace_to_delete_drawing/cursor')
 end
 
+function test_backspace_from_start_of_final_line()
+  io.write('\ntest_backspace_from_start_of_final_line')
+  -- display final line of text with cursor at start of it
+  App.screen.init{width=120, height=60}
+  Editor_state = edit.initialize_test_state()
+  Editor_state.lines = load_array{'abc', 'def'}
+  Editor_state.screen_top1 = {line=2, pos=1}
+  Editor_state.cursor1 = {line=2, pos=1}
+  Text.redraw_all(Editor_state)
+  -- backspace scrolls up
+  edit.run_after_keychord(Editor_state, 'backspace')
+  check_eq(#Editor_state.lines, 1, 'F - test_backspace_from_start_of_final_line/#lines')
+  check_eq(Editor_state.cursor1.line, 1, 'F - test_backspace_from_start_of_final_line/cursor')
+  check_eq(Editor_state.screen_top1.line, 1, 'F - test_backspace_from_start_of_final_line/screen_top')
+end
+
 function test_insert_first_character()
   io.write('\ntest_insert_first_character')
   App.screen.init{width=120, height=60}
@@ -1068,6 +1084,23 @@ function test_pagedown_can_start_from_middle_of_long_wrapping_line()
   App.screen.check(y, 'mno ', 'F - test_pagedown_can_start_from_middle_of_long_wrapping_line/screen:3')
 end
 
+function test_pagedown_never_moves_up()
+  io.write('\ntest_pagedown_never_moves_up')
+  -- draw the final screen line of a wrapping line
+  App.screen.init{width=Editor_state.left+30, height=60}
+  Editor_state = edit.initialize_test_state()
+  Editor_state.lines = load_array{'abc def ghi'}
+  Text.redraw_all(Editor_state)
+  Editor_state.cursor1 = {line=1, pos=9}
+  Editor_state.screen_top1 = {line=1, pos=9}
+  Editor_state.screen_bottom1 = {}
+  edit.draw(Editor_state)
+  -- pagedown makes no change
+  edit.run_after_keychord(Editor_state, 'pagedown')
+  check_eq(Editor_state.screen_top1.line, 1, 'F - test_pagedown_never_moves_up/screen_top:line')
+  check_eq(Editor_state.screen_top1.pos, 9, 'F - test_pagedown_never_moves_up/screen_top:pos')
+end
+
 function test_down_arrow_moves_cursor()
   io.write('\ntest_down_arrow_moves_cursor')
   App.screen.init{width=120, height=60}