diff --git a/edit.lua b/edit.lua
index e8a8f03..533408d 100644
--- a/edit.lua
+++ b/edit.lua
@@ -65,11 +65,6 @@ function edit.initialize_state(top, left, right, font_height, line_height)  -- c
     width = right-left,
 
     filename = love.filesystem.getUserDirectory()..'/lines.txt',
-    next_save = nil,
-
-    -- undo
-    history = {},
-    next_history = 1,
 
     -- search
     search_term = nil,
@@ -111,23 +106,9 @@ function edit.draw(State)
 end
 
 function edit.update(State, dt)
-  if State.next_save and State.next_save < App.getTime() then
-    save_to_disk(State)
-    State.next_save = nil
-  end
-end
-
-function schedule_save(State)
-  if State.next_save == nil then
-    State.next_save = App.getTime() + 3  -- short enough that you're likely to still remember what you did
-  end
 end
 
 function edit.quit(State)
-  -- make sure to save before quitting
-  if State.next_save then
-    save_to_disk(State)
-  end
 end
 
 function edit.mouse_pressed(State, x,y, mouse_button)
@@ -193,10 +174,7 @@ function edit.textinput(State, t)
     State.search_term = State.search_term..t
     State.search_text = nil
     Text.search_next(State)
-  else
-    Text.textinput(State, t)
   end
-  schedule_save(State)
 end
 
 function edit.keychord_pressed(State, chord, key)
@@ -245,67 +223,12 @@ function edit.keychord_pressed(State, chord, key)
   elseif chord == 'C-0' then
     edit.update_font_settings(State, 20)
     Text.redraw_all(State)
-  -- undo
-  elseif chord == 'C-z' then
-    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
-    local event = undo_event(State)
-    if event then
-      local src = event.before
-      State.screen_top1 = deepcopy(src.screen_top)
-      State.cursor1 = deepcopy(src.cursor)
-      State.selection1 = deepcopy(src.selection)
-      patch(State.lines, event.after, event.before)
-      patch_placeholders(State.line_cache, event.after, event.before)
-      -- if we're scrolling, reclaim all fragments to avoid memory leaks
-      Text.redraw_all(State)
-      schedule_save(State)
-    end
-  elseif chord == 'C-y' then
-    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
-    local event = redo_event(State)
-    if event then
-      local src = event.after
-      State.screen_top1 = deepcopy(src.screen_top)
-      State.cursor1 = deepcopy(src.cursor)
-      State.selection1 = deepcopy(src.selection)
-      patch(State.lines, event.before, event.after)
-      -- if we're scrolling, reclaim all fragments to avoid memory leaks
-      Text.redraw_all(State)
-      schedule_save(State)
-    end
   -- clipboard
   elseif chord == 'C-c' then
     local s = Text.selection(State)
     if s then
       App.setClipboardText(s)
     end
-  elseif chord == 'C-x' then
-    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
-    local s = Text.cut_selection(State, State.left, State.right)
-    if s then
-      App.setClipboardText(s)
-    end
-    schedule_save(State)
-  elseif chord == 'C-v' then
-    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
-    -- We don't have a good sense of when to scroll, so we'll be conservative
-    -- and sometimes scroll when we didn't quite need to.
-    local before_line = State.cursor1.line
-    local before = snapshot(State, before_line)
-    local clipboard_data = App.getClipboardText()
-    for _,code in utf8.codes(clipboard_data) do
-      local c = utf8.char(code)
-      if c == '\n' then
-        Text.insert_return(State)
-      else
-        Text.insert_at_cursor(State, c)
-      end
-    end
-    if Text.cursor_out_of_screen(State) then
-      Text.snap_cursor_to_bottom_of_screen(State, State.left, State.right)
-    end
-    schedule_save(State)
-    record_undo_event(State, {before=before, after=snapshot(State, before_line, State.cursor1.line)})
   -- dispatch to text
   else
     for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
diff --git a/main_tests.lua b/main_tests.lua
index 31605f0..5c72064 100644
--- a/main_tests.lua
+++ b/main_tests.lua
@@ -44,33 +44,3 @@ function test_drop_file()
   check_eq(Editor_state.lines[3].data, 'ghi', 'F - test_drop_file/lines:3')
   edit.draw(Editor_state)
 end
-
-function test_drop_file_saves_previous()
-  io.write('\ntest_drop_file_saves_previous')
-  App.screen.init{width=Editor_state.left+300, height=300}
-  -- initially editing a file called foo that hasn't been saved to filesystem yet
-  Editor_state.lines = load_array{'abc', 'def'}
-  Editor_state.filename = 'foo'
-  schedule_save(Editor_state)
-  -- now drag a new file bar from the filesystem
-  App.filesystem['bar'] = 'abc\ndef\nghi\n'
-  local fake_dropped_file = {
-    opened = false,
-    getFilename = function(self)
-                    return 'bar'
-                  end,
-    open = function(self)
-             self.opened = true
-           end,
-    lines = function(self)
-              assert(self.opened)
-              return App.filesystem['bar']:gmatch('[^\n]+')
-            end,
-    close = function(self)
-              self.opened = false
-            end,
-  }
-  App.filedropped(fake_dropped_file)
-  -- filesystem now contains a file called foo
-  check_eq(App.filesystem['foo'], 'abc\ndef\n', 'F - test_drop_file_saves_previous')
-end
diff --git a/select.lua b/select.lua
index b7cf65f..7baa398 100644
--- a/select.lua
+++ b/select.lua
@@ -95,60 +95,6 @@ function Text.to_pos(State, x,y)
   end
 end
 
-function Text.cut_selection(State)
-  if State.selection1.line == nil then return end
-  local result = Text.selection(State)
-  Text.delete_selection(State)
-  return result
-end
-
-function Text.delete_selection(State)
-  if State.selection1.line == nil then return end
-  local minl,maxl = minmax(State.selection1.line, State.cursor1.line)
-  local before = snapshot(State, minl, maxl)
-  Text.delete_selection_without_undo(State)
-  record_undo_event(State, {before=before, after=snapshot(State, State.cursor1.line)})
-end
-
-function Text.delete_selection_without_undo(State)
-  if State.selection1.line == nil then return end
-  -- min,max = sorted(State.selection1,State.cursor1)
-  local minl,minp = State.selection1.line,State.selection1.pos
-  local maxl,maxp = State.cursor1.line,State.cursor1.pos
-  if minl > maxl then
-    minl,maxl = maxl,minl
-    minp,maxp = maxp,minp
-  elseif minl == maxl then
-    if minp > maxp then
-      minp,maxp = maxp,minp
-    end
-  end
-  -- update State.cursor1 and State.selection1
-  State.cursor1.line = minl
-  State.cursor1.pos = minp
-  if Text.lt1(State.cursor1, State.screen_top1) then
-    State.screen_top1.line = State.cursor1.line
-    State.screen_top1.pos = Text.pos_at_start_of_screen_line(State, State.cursor1)
-  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)
-    return
-  end
-  assert(minl < maxl)
-  local rhs = State.lines[maxl].data:sub(max_offset)
-  for i=maxl,minl+1,-1 do
-    table.remove(State.lines, i)
-    table.remove(State.line_cache, i)
-  end
-  State.lines[minl].data = State.lines[minl].data:sub(1, min_offset-1)..rhs
-end
-
 function Text.selection(State)
   if State.selection1.line == nil then return end
   -- min,max = sorted(State.selection1,State.cursor1)
diff --git a/text.lua b/text.lua
index 0e79e8d..414f86c 100644
--- a/text.lua
+++ b/text.lua
@@ -3,7 +3,6 @@ Text = {}
 
 require 'search'
 require 'select'
-require 'undo'
 require 'text_tests'
 
 -- draw a line starting from startpos to screen at y between State.left and State.right
@@ -150,128 +149,11 @@ function Text.compute_fragments(State, line_index)
   end
 end
 
-function Text.textinput(State, t)
-  if App.mouse_down(1) then return end
-  if App.ctrl_down() or App.alt_down() or App.cmd_down() then return end
-  local before = snapshot(State, State.cursor1.line)
---?   print(State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
-  Text.insert_at_cursor(State, t)
-  if State.cursor_y > App.screen.height - State.line_height then
-    Text.populate_screen_line_starting_pos(State, State.cursor1.line)
-    Text.snap_cursor_to_bottom_of_screen(State, State.left, State.right)
---?     print('=>', State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
-  end
-  record_undo_event(State, {before=before, after=snapshot(State, State.cursor1.line)})
-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)
-  State.cursor1.pos = State.cursor1.pos+1
-end
-
 -- Don't handle any keys here that would trigger love.textinput above.
 function Text.keychord_pressed(State, chord)
 --?   print('chord', chord, State.selection1.line, State.selection1.pos)
-  --== shortcuts that mutate text
-  if chord == 'return' then
-    local before_line = State.cursor1.line
-    local before = snapshot(State, before_line)
-    Text.insert_return(State)
-    State.selection1 = {}
-    if State.cursor_y > App.screen.height - State.line_height then
-      Text.snap_cursor_to_bottom_of_screen(State, State.left, State.right)
-    end
-    schedule_save(State)
-    record_undo_event(State, {before=before, after=snapshot(State, before_line, State.cursor1.line)})
-  elseif chord == 'tab' then
-    local before = snapshot(State, State.cursor1.line)
---?     print(State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
-    Text.insert_at_cursor(State, '\t')
-    if State.cursor_y > App.screen.height - State.line_height then
-      Text.populate_screen_line_starting_pos(State, State.cursor1.line)
-      Text.snap_cursor_to_bottom_of_screen(State, State.left, State.right)
---?       print('=>', State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos, State.screen_bottom1.line, State.screen_bottom1.pos)
-    end
-    schedule_save(State)
-    record_undo_event(State, {before=before, after=snapshot(State, State.cursor1.line)})
-  elseif chord == 'backspace' then
-    if State.selection1.line then
-      Text.delete_selection(State, State.left, State.right)
-      schedule_save(State)
-      return
-    end
-    local before
-    if State.cursor1.pos > 1 then
-      before = snapshot(State, State.cursor1.line)
-      local byte_start = utf8.offset(State.lines[State.cursor1.line].data, State.cursor1.pos-1)
-      local byte_end = utf8.offset(State.lines[State.cursor1.line].data, State.cursor1.pos)
-      if byte_start then
-        if byte_end then
-          State.lines[State.cursor1.line].data = string.sub(State.lines[State.cursor1.line].data, 1, byte_start-1)..string.sub(State.lines[State.cursor1.line].data, byte_end)
-        else
-          State.lines[State.cursor1.line].data = string.sub(State.lines[State.cursor1.line].data, 1, byte_start-1)
-        end
-        State.cursor1.pos = State.cursor1.pos-1
-      end
-    elseif State.cursor1.line > 1 then
-      before = snapshot(State, State.cursor1.line-1, State.cursor1.line)
-      -- join lines
-      State.cursor1.pos = utf8.len(State.lines[State.cursor1.line-1].data)+1
-      State.lines[State.cursor1.line-1].data = State.lines[State.cursor1.line-1].data..State.lines[State.cursor1.line].data
-      table.remove(State.lines, State.cursor1.line)
-      table.remove(State.line_cache, State.cursor1.line)
-      State.cursor1.line = State.cursor1.line-1
-    end
-    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
-    end
-    Text.clear_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)})
-  elseif chord == 'delete' then
-    if State.selection1.line then
-      Text.delete_selection(State, State.left, State.right)
-      schedule_save(State)
-      return
-    end
-    local before
-    if State.cursor1.pos <= utf8.len(State.lines[State.cursor1.line].data) then
-      before = snapshot(State, State.cursor1.line)
-    else
-      before = snapshot(State, State.cursor1.line, State.cursor1.line+1)
-    end
-    if State.cursor1.pos <= utf8.len(State.lines[State.cursor1.line].data) then
-      local byte_start = utf8.offset(State.lines[State.cursor1.line].data, State.cursor1.pos)
-      local byte_end = utf8.offset(State.lines[State.cursor1.line].data, State.cursor1.pos+1)
-      if byte_start then
-        if byte_end then
-          State.lines[State.cursor1.line].data = string.sub(State.lines[State.cursor1.line].data, 1, byte_start-1)..string.sub(State.lines[State.cursor1.line].data, byte_end)
-        else
-          State.lines[State.cursor1.line].data = string.sub(State.lines[State.cursor1.line].data, 1, byte_start-1)
-        end
-        -- no change to State.cursor1.pos
-      end
-    elseif State.cursor1.line < #State.lines then
-      -- join lines
-      State.lines[State.cursor1.line].data = State.lines[State.cursor1.line].data..State.lines[State.cursor1.line+1].data
-      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)
-    schedule_save(State)
-    record_undo_event(State, {before=before, after=snapshot(State, State.cursor1.line)})
   --== shortcuts that move the cursor
-  elseif chord == 'left' then
+  if chord == 'left' then
     Text.left(State)
     State.selection1 = {}
   elseif chord == 'right' then
@@ -355,16 +237,6 @@ function Text.keychord_pressed(State, chord)
   end
 end
 
-function Text.insert_return(State)
-  local byte_offset = Text.offset(State.lines[State.cursor1.line].data, State.cursor1.pos)
-  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)
-  State.cursor1.line = State.cursor1.line+1
-  State.cursor1.pos = 1
-end
-
 function Text.pageup(State)
 --?   print('pageup')
   -- duplicate some logic from love.draw
diff --git a/text_tests.lua b/text_tests.lua
index 7f9b2e4..0e6a2d7 100644
--- a/text_tests.lua
+++ b/text_tests.lua
@@ -14,47 +14,6 @@ function test_initial_state()
   check_eq(Editor_state.screen_top1.pos, 1, 'F - test_initial_state/screen_top:pos')
 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}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{}
-  Text.redraw_all(Editor_state)
-  edit.draw(Editor_state)
-  edit.run_after_textinput(Editor_state, 'a')
-  local y = Editor_state.top
-  App.screen.check(y, 'a', 'F - test_insert_first_character/screen:1')
-end
-
-function test_press_ctrl()
-  io.write('\ntest_press_ctrl')
-  -- press ctrl while the cursor is on text
-  App.screen.init{width=50, height=80}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{''}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=1}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.run_after_keychord(Editor_state, 'C-m')
-end
-
 function test_move_left()
   io.write('\ntest_move_left')
   App.screen.init{width=120, height=60}
@@ -604,47 +563,6 @@ function test_cursor_movement_without_shift_resets_selection()
   check_eq(Editor_state.lines[1].data, 'abc', 'F - test_cursor_movement_without_shift_resets_selection/data')
 end
 
-function test_edit_deletes_selection()
-  io.write('\ntest_edit_deletes_selection')
-  -- display a line of text with some part selected
-  App.screen.init{width=75, height=80}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=1}
-  Editor_state.selection1 = {line=1, pos=2}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  -- press a key
-  edit.run_after_textinput(Editor_state, 'x')
-  -- selected text is deleted and replaced with the key
-  check_eq(Editor_state.lines[1].data, 'xbc', 'F - test_edit_deletes_selection')
-end
-
-function test_edit_with_shift_key_deletes_selection()
-  io.write('\ntest_edit_with_shift_key_deletes_selection')
-  -- display a line of text with some part selected
-  App.screen.init{width=75, height=80}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=1}
-  Editor_state.selection1 = {line=1, pos=2}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  -- mimic precise keypresses for a capital letter
-  App.fake_key_press('lshift')
-  edit.keychord_pressed(Editor_state, 'd', 'd')
-  edit.textinput(Editor_state, 'D')
-  edit.key_released(Editor_state, 'd')
-  App.fake_key_release('lshift')
-  -- selected text is deleted and replaced with the key
-  check_nil(Editor_state.selection1.line, 'F - test_edit_with_shift_key_deletes_selection')
-  check_eq(Editor_state.lines[1].data, 'Dbc', 'F - test_edit_with_shift_key_deletes_selection/data')
-end
-
 function test_copy_does_not_reset_selection()
   io.write('\ntest_copy_does_not_reset_selection')
   -- display a line of text with a selection
@@ -664,170 +582,6 @@ function test_copy_does_not_reset_selection()
   check(Editor_state.selection1.line, 'F - test_copy_does_not_reset_selection')
 end
 
-function test_cut()
-  io.write('\ntest_cut')
-  -- display a line of text with some part selected
-  App.screen.init{width=75, height=80}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=1}
-  Editor_state.selection1 = {line=1, pos=2}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  -- press a key
-  edit.run_after_keychord(Editor_state, 'C-x')
-  check_eq(App.clipboard, 'a', 'F - test_cut/clipboard')
-  -- selected text is deleted
-  check_eq(Editor_state.lines[1].data, 'bc', 'F - test_cut/data')
-end
-
-function test_paste_replaces_selection()
-  io.write('\ntest_paste_replaces_selection')
-  -- display a line of text with a selection
-  App.screen.init{width=75, height=80}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'def'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=2, pos=1}
-  Editor_state.selection1 = {line=1, pos=1}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  -- set clipboard
-  App.clipboard = 'xyz'
-  -- paste selection
-  edit.run_after_keychord(Editor_state, 'C-v')
-  -- selection is reset since shift key is not pressed
-  -- selection includes the newline, so it's also deleted
-  check_eq(Editor_state.lines[1].data, 'xyzdef', 'F - test_paste_replaces_selection')
-end
-
-function test_deleting_selection_may_scroll()
-  io.write('\ntest_deleting_selection_may_scroll')
-  -- display lines 2/3/4
-  App.screen.init{width=120, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=3, pos=2}
-  Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  local y = Editor_state.top
-  App.screen.check(y, 'def', 'F - test_deleting_selection_may_scroll/baseline/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'ghi', 'F - test_deleting_selection_may_scroll/baseline/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'jkl', 'F - test_deleting_selection_may_scroll/baseline/screen:3')
-  -- set up a selection starting above the currently displayed page
-  Editor_state.selection1 = {line=1, pos=2}
-  -- delete selection
-  edit.run_after_keychord(Editor_state, 'backspace')
-  -- page scrolls up
-  check_eq(Editor_state.screen_top1.line, 1, 'F - test_deleting_selection_may_scroll')
-  check_eq(Editor_state.lines[1].data, 'ahi', 'F - test_deleting_selection_may_scroll/data')
-end
-
-function test_edit_wrapping_text()
-  io.write('\ntest_edit_wrapping_text')
-  App.screen.init{width=50, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'def', 'xyz'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=2, pos=4}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  edit.run_after_textinput(Editor_state, 'g')
-  local y = Editor_state.top
-  App.screen.check(y, 'abc', 'F - test_edit_wrapping_text/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'de', 'F - test_edit_wrapping_text/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'fg', 'F - test_edit_wrapping_text/screen:3')
-end
-
-function test_insert_newline()
-  io.write('\ntest_insert_newline')
-  -- display a few lines
-  App.screen.init{width=Editor_state.left+30, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=2}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  local y = Editor_state.top
-  App.screen.check(y, 'abc', 'F - test_insert_newline/baseline/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'def', 'F - test_insert_newline/baseline/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'ghi', 'F - test_insert_newline/baseline/screen:3')
-  -- hitting the enter key splits the line
-  edit.run_after_keychord(Editor_state, 'return')
-  check_eq(Editor_state.screen_top1.line, 1, 'F - test_insert_newline/screen_top')
-  check_eq(Editor_state.cursor1.line, 2, 'F - test_insert_newline/cursor:line')
-  check_eq(Editor_state.cursor1.pos, 1, 'F - test_insert_newline/cursor:pos')
-  y = Editor_state.top
-  App.screen.check(y, 'a', 'F - test_insert_newline/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'bc', 'F - test_insert_newline/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'def', 'F - test_insert_newline/screen:3')
-end
-
-function test_insert_newline_at_start_of_line()
-  io.write('\ntest_insert_newline_at_start_of_line')
-  -- display a line
-  App.screen.init{width=Editor_state.left+30, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=1}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  -- hitting the enter key splits the line
-  edit.run_after_keychord(Editor_state, 'return')
-  check_eq(Editor_state.cursor1.line, 2, 'F - test_insert_newline_at_start_of_line/cursor:line')
-  check_eq(Editor_state.cursor1.pos, 1, 'F - test_insert_newline_at_start_of_line/cursor:pos')
-  check_eq(Editor_state.lines[1].data, '', 'F - test_insert_newline_at_start_of_line/data:1')
-  check_eq(Editor_state.lines[2].data, 'abc', 'F - test_insert_newline_at_start_of_line/data:2')
-end
-
-function test_insert_from_clipboard()
-  io.write('\ntest_insert_from_clipboard')
-  -- display a few lines
-  App.screen.init{width=Editor_state.left+30, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=2}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  local y = Editor_state.top
-  App.screen.check(y, 'abc', 'F - test_insert_from_clipboard/baseline/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'def', 'F - test_insert_from_clipboard/baseline/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'ghi', 'F - test_insert_from_clipboard/baseline/screen:3')
-  -- paste some text including a newline, check that new line is created
-  App.clipboard = 'xy\nz'
-  edit.run_after_keychord(Editor_state, 'C-v')
-  check_eq(Editor_state.screen_top1.line, 1, 'F - test_insert_from_clipboard/screen_top')
-  check_eq(Editor_state.cursor1.line, 2, 'F - test_insert_from_clipboard/cursor:line')
-  check_eq(Editor_state.cursor1.pos, 2, 'F - test_insert_from_clipboard/cursor:pos')
-  y = Editor_state.top
-  App.screen.check(y, 'axy', 'F - test_insert_from_clipboard/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'zbc', 'F - test_insert_from_clipboard/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'def', 'F - test_insert_from_clipboard/screen:3')
-end
-
 function test_move_cursor_using_mouse()
   io.write('\ntest_move_cursor_using_mouse')
   App.screen.init{width=50, height=60}
@@ -923,24 +677,6 @@ function test_select_text_repeatedly_using_mouse_and_shift()
   check_eq(Editor_state.cursor1.pos, 2, 'F - test_select_text_repeatedly_using_mouse_and_shift/cursor:pos')
 end
 
-function test_cut_without_selection()
-  io.write('\ntest_cut_without_selection')
-  -- display a few lines
-  App.screen.init{width=Editor_state.left+30, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=2}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  Editor_state.selection1 = {}
-  edit.draw(Editor_state)
-  -- try to cut without selecting text
-  edit.run_after_keychord(Editor_state, 'C-x')
-  -- no crash
-  check_nil(Editor_state.selection1.line, 'F - test_cut_without_selection')
-end
-
 function test_pagedown()
   io.write('\ntest_pagedown')
   App.screen.init{width=120, height=45}
@@ -1427,112 +1163,6 @@ function test_pageup_scrolls_up_from_middle_screen_line()
   App.screen.check(y, 'ghi ', 'F - test_pageup_scrolls_up_from_middle_screen_line/screen:3')
 end
 
-function test_enter_on_bottom_line_scrolls_down()
-  io.write('\ntest_enter_on_bottom_line_scrolls_down')
-  -- display a few lines with cursor on bottom 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', 'jkl'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=3, pos=2}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  local y = Editor_state.top
-  App.screen.check(y, 'abc', 'F - test_enter_on_bottom_line_scrolls_down/baseline/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'def', 'F - test_enter_on_bottom_line_scrolls_down/baseline/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'ghi', 'F - test_enter_on_bottom_line_scrolls_down/baseline/screen:3')
-  -- after hitting the enter key the screen scrolls down
-  edit.run_after_keychord(Editor_state, 'return')
-  check_eq(Editor_state.screen_top1.line, 2, 'F - test_enter_on_bottom_line_scrolls_down/screen_top')
-  check_eq(Editor_state.cursor1.line, 4, 'F - test_enter_on_bottom_line_scrolls_down/cursor:line')
-  check_eq(Editor_state.cursor1.pos, 1, 'F - test_enter_on_bottom_line_scrolls_down/cursor:pos')
-  y = Editor_state.top
-  App.screen.check(y, 'def', 'F - test_enter_on_bottom_line_scrolls_down/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'g', 'F - test_enter_on_bottom_line_scrolls_down/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'hi', 'F - test_enter_on_bottom_line_scrolls_down/screen:3')
-end
-
-function test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom()
-  io.write('\ntest_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom')
-  -- display just the bottom line on screen
-  App.screen.init{width=Editor_state.left+30, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=4, pos=2}
-  Editor_state.screen_top1 = {line=4, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  local y = Editor_state.top
-  App.screen.check(y, 'jkl', 'F - test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom/baseline/screen:1')
-  -- after hitting the enter key the screen does not scroll down
-  edit.run_after_keychord(Editor_state, 'return')
-  check_eq(Editor_state.screen_top1.line, 4, 'F - test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom/screen_top')
-  check_eq(Editor_state.cursor1.line, 5, 'F - test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom/cursor:line')
-  check_eq(Editor_state.cursor1.pos, 1, 'F - test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom/cursor:pos')
-  y = Editor_state.top
-  App.screen.check(y, 'j', 'F - test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'kl', 'F - test_enter_on_final_line_avoids_scrolling_down_when_not_at_bottom/screen:2')
-end
-
-function test_inserting_text_on_final_line_avoids_scrolling_down_when_not_at_bottom()
-  io.write('\ntest_inserting_text_on_final_line_avoids_scrolling_down_when_not_at_bottom')
-  -- display just an empty bottom line on screen
-  App.screen.init{width=Editor_state.left+30, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', ''}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=2, pos=1}
-  Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  -- after hitting the inserting_text key the screen does not scroll down
-  edit.run_after_textinput(Editor_state, 'a')
-  check_eq(Editor_state.screen_top1.line, 2, 'F - test_inserting_text_on_final_line_avoids_scrolling_down_when_not_at_bottom/screen_top')
-  check_eq(Editor_state.cursor1.line, 2, 'F - test_inserting_text_on_final_line_avoids_scrolling_down_when_not_at_bottom/cursor:line')
-  check_eq(Editor_state.cursor1.pos, 2, 'F - test_inserting_text_on_final_line_avoids_scrolling_down_when_not_at_bottom/cursor:pos')
-  local y = Editor_state.top
-  App.screen.check(y, 'a', 'F - test_inserting_text_on_final_line_avoids_scrolling_down_when_not_at_bottom/screen:1')
-end
-
-function test_typing_on_bottom_line_scrolls_down()
-  io.write('\ntest_typing_on_bottom_line_scrolls_down')
-  -- display a few lines with cursor on bottom 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', 'jkl'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=3, pos=4}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  local y = Editor_state.top
-  App.screen.check(y, 'abc', 'F - test_typing_on_bottom_line_scrolls_down/baseline/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'def', 'F - test_typing_on_bottom_line_scrolls_down/baseline/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'ghi', 'F - test_typing_on_bottom_line_scrolls_down/baseline/screen:3')
-  -- after typing something the line wraps and the screen scrolls down
-  edit.run_after_textinput(Editor_state, 'j')
-  edit.run_after_textinput(Editor_state, 'k')
-  edit.run_after_textinput(Editor_state, 'l')
-  check_eq(Editor_state.screen_top1.line, 2, 'F - test_typing_on_bottom_line_scrolls_down/screen_top')
-  check_eq(Editor_state.cursor1.line, 3, 'F - test_typing_on_bottom_line_scrolls_down/cursor:line')
-  check_eq(Editor_state.cursor1.pos, 7, 'F - test_typing_on_bottom_line_scrolls_down/cursor:pos')
-  y = Editor_state.top
-  App.screen.check(y, 'def', 'F - test_typing_on_bottom_line_scrolls_down/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'ghij', 'F - test_typing_on_bottom_line_scrolls_down/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'kl', '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
@@ -1655,311 +1285,6 @@ function test_end_scrolls_down_in_wrapped_line()
   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')
-  App.screen.init{width=100, height=200}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc def ghi jkl mno pqr ', 'xyz'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=25}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  local y = Editor_state.top
-  App.screen.check(y, 'abc def ghi ', 'F - test_position_cursor_on_recently_edited_wrapping_line/baseline1/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'jkl mno pqr ', 'F - test_position_cursor_on_recently_edited_wrapping_line/baseline1/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'xyz', 'F - test_position_cursor_on_recently_edited_wrapping_line/baseline1/screen:3')
-  -- add to the line until it's wrapping over 3 screen lines
-  edit.run_after_textinput(Editor_state, 's')
-  edit.run_after_textinput(Editor_state, 't')
-  edit.run_after_textinput(Editor_state, 'u')
-  check_eq(Editor_state.cursor1.pos, 28, 'F - test_position_cursor_on_recently_edited_wrapping_line/cursor:pos')
-  y = Editor_state.top
-  App.screen.check(y, 'abc def ghi ', 'F - test_position_cursor_on_recently_edited_wrapping_line/baseline2/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'jkl mno pqr ', 'F - test_position_cursor_on_recently_edited_wrapping_line/baseline2/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'stu', 'F - test_position_cursor_on_recently_edited_wrapping_line/baseline2/screen:3')
-  -- try to move the cursor earlier in the third screen line by clicking the mouse
-  edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+Editor_state.line_height*2+5, 1)
-  -- cursor should move
-  check_eq(Editor_state.cursor1.line, 1, 'F - test_position_cursor_on_recently_edited_wrapping_line/cursor:line')
-  check_eq(Editor_state.cursor1.pos, 26, 'F - test_position_cursor_on_recently_edited_wrapping_line/cursor:pos')
-end
-
-function test_backspace_can_scroll_up()
-  io.write('\ntest_backspace_can_scroll_up')
-  -- display the lines 2/3/4 with the cursor on line 2
-  App.screen.init{width=120, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=2, pos=1}
-  Editor_state.screen_top1 = {line=2, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  local y = Editor_state.top
-  App.screen.check(y, 'def', 'F - test_backspace_can_scroll_up/baseline/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'ghi', 'F - test_backspace_can_scroll_up/baseline/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'jkl', 'F - test_backspace_can_scroll_up/baseline/screen:3')
-  -- after hitting backspace the screen scrolls up by one line
-  edit.run_after_keychord(Editor_state, 'backspace')
-  check_eq(Editor_state.screen_top1.line, 1, 'F - test_backspace_can_scroll_up/screen_top')
-  check_eq(Editor_state.cursor1.line, 1, 'F - test_backspace_can_scroll_up/cursor')
-  y = Editor_state.top
-  App.screen.check(y, 'abcdef', 'F - test_backspace_can_scroll_up/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'ghi', 'F - test_backspace_can_scroll_up/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'jkl', 'F - test_backspace_can_scroll_up/screen:3')
-end
-
-function test_backspace_can_scroll_up_screen_line()
-  io.write('\ntest_backspace_can_scroll_up_screen_line')
-  -- display lines starting from second screen line of a 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 jkl', 'mno'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=3, pos=5}
-  Editor_state.screen_top1 = {line=3, pos=5}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  local y = Editor_state.top
-  App.screen.check(y, 'jkl', 'F - test_backspace_can_scroll_up_screen_line/baseline/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'mno', 'F - test_backspace_can_scroll_up_screen_line/baseline/screen:2')
-  -- after hitting backspace the screen scrolls up by one screen line
-  edit.run_after_keychord(Editor_state, 'backspace')
-  y = Editor_state.top
-  App.screen.check(y, 'ghij', 'F - test_backspace_can_scroll_up_screen_line/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'kl', 'F - test_backspace_can_scroll_up_screen_line/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'mno', 'F - test_backspace_can_scroll_up_screen_line/screen:3')
-  check_eq(Editor_state.screen_top1.line, 3, 'F - test_backspace_can_scroll_up_screen_line/screen_top')
-  check_eq(Editor_state.screen_top1.pos, 1, 'F - test_backspace_can_scroll_up_screen_line/screen_top')
-  check_eq(Editor_state.cursor1.line, 3, 'F - test_backspace_can_scroll_up_screen_line/cursor:line')
-  check_eq(Editor_state.cursor1.pos, 4, 'F - test_backspace_can_scroll_up_screen_line/cursor:pos')
-end
-
-function test_backspace_past_line_boundary()
-  io.write('\ntest_backspace_past_line_boundary')
-  -- position cursor at start of a (non-first) line
-  App.screen.init{width=Editor_state.left+30, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'def'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=2, pos=1}
-  -- backspace joins with previous line
-  edit.run_after_keychord(Editor_state, 'backspace')
-  check_eq(Editor_state.lines[1].data, 'abcdef', "F - test_backspace_past_line_boundary")
-end
-
--- some tests for operating over selections created using Shift- chords
--- we're just testing delete_selection, and it works the same for all keys
-
-function test_backspace_over_selection()
-  io.write('\ntest_backspace_over_selection')
-  -- select just one character within a line with cursor before selection
-  App.screen.init{width=Editor_state.left+30, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl', 'mno'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=1}
-  Editor_state.selection1 = {line=1, pos=2}
-  -- backspace deletes the selected character, even though it's after the cursor
-  edit.run_after_keychord(Editor_state, 'backspace')
-  check_eq(Editor_state.lines[1].data, 'bc', "F - test_backspace_over_selection/data")
-  -- cursor (remains) at start of selection
-  check_eq(Editor_state.cursor1.line, 1, "F - test_backspace_over_selection/cursor:line")
-  check_eq(Editor_state.cursor1.pos, 1, "F - test_backspace_over_selection/cursor:pos")
-  -- selection is cleared
-  check_nil(Editor_state.selection1.line, "F - test_backspace_over_selection/selection")
-end
-
-function test_backspace_over_selection_reverse()
-  io.write('\ntest_backspace_over_selection_reverse')
-  -- select just one character within a line with cursor after selection
-  App.screen.init{width=Editor_state.left+30, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl', 'mno'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=2}
-  Editor_state.selection1 = {line=1, pos=1}
-  -- backspace deletes the selected character
-  edit.run_after_keychord(Editor_state, 'backspace')
-  check_eq(Editor_state.lines[1].data, 'bc', "F - test_backspace_over_selection_reverse/data")
-  -- cursor moves to start of selection
-  check_eq(Editor_state.cursor1.line, 1, "F - test_backspace_over_selection_reverse/cursor:line")
-  check_eq(Editor_state.cursor1.pos, 1, "F - test_backspace_over_selection_reverse/cursor:pos")
-  -- selection is cleared
-  check_nil(Editor_state.selection1.line, "F - test_backspace_over_selection_reverse/selection")
-end
-
-function test_backspace_over_multiple_lines()
-  io.write('\ntest_backspace_over_multiple_lines')
-  -- select just one character within a line with cursor after selection
-  App.screen.init{width=Editor_state.left+30, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'def', 'ghi', 'jkl', 'mno'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=2}
-  Editor_state.selection1 = {line=4, pos=2}
-  -- backspace deletes the region and joins the remaining portions of lines on either side
-  edit.run_after_keychord(Editor_state, 'backspace')
-  check_eq(Editor_state.lines[1].data, 'akl', "F - test_backspace_over_multiple_lines/data:1")
-  check_eq(Editor_state.lines[2].data, 'mno', "F - test_backspace_over_multiple_lines/data:2")
-  -- cursor remains at start of selection
-  check_eq(Editor_state.cursor1.line, 1, "F - test_backspace_over_multiple_lines/cursor:line")
-  check_eq(Editor_state.cursor1.pos, 2, "F - test_backspace_over_multiple_lines/cursor:pos")
-  -- selection is cleared
-  check_nil(Editor_state.selection1.line, "F - test_backspace_over_multiple_lines/selection")
-end
-
-function test_backspace_to_end_of_line()
-  io.write('\ntest_backspace_to_end_of_line')
-  -- select region from cursor to end of 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', 'jkl', 'mno'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=2}
-  Editor_state.selection1 = {line=1, pos=4}
-  -- backspace deletes rest of line without joining to any other line
-  edit.run_after_keychord(Editor_state, 'backspace')
-  check_eq(Editor_state.lines[1].data, 'a', "F - test_backspace_to_start_of_line/data:1")
-  check_eq(Editor_state.lines[2].data, 'def', "F - test_backspace_to_start_of_line/data:2")
-  -- cursor remains at start of selection
-  check_eq(Editor_state.cursor1.line, 1, "F - test_backspace_to_start_of_line/cursor:line")
-  check_eq(Editor_state.cursor1.pos, 2, "F - test_backspace_to_start_of_line/cursor:pos")
-  -- selection is cleared
-  check_nil(Editor_state.selection1.line, "F - test_backspace_to_start_of_line/selection")
-end
-
-function test_backspace_to_start_of_line()
-  io.write('\ntest_backspace_to_start_of_line')
-  -- select region from cursor to start of 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', 'jkl', 'mno'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=2, pos=1}
-  Editor_state.selection1 = {line=2, pos=3}
-  -- backspace deletes beginning of line without joining to any other line
-  edit.run_after_keychord(Editor_state, 'backspace')
-  check_eq(Editor_state.lines[1].data, 'abc', "F - test_backspace_to_start_of_line/data:1")
-  check_eq(Editor_state.lines[2].data, 'f', "F - test_backspace_to_start_of_line/data:2")
-  -- cursor remains at start of selection
-  check_eq(Editor_state.cursor1.line, 2, "F - test_backspace_to_start_of_line/cursor:line")
-  check_eq(Editor_state.cursor1.pos, 1, "F - test_backspace_to_start_of_line/cursor:pos")
-  -- selection is cleared
-  check_nil(Editor_state.selection1.line, "F - test_backspace_to_start_of_line/selection")
-end
-
-function test_undo_insert_text()
-  io.write('\ntest_undo_insert_text')
-  App.screen.init{width=120, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'def', 'xyz'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=2, pos=4}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  -- insert a character
-  edit.draw(Editor_state)
-  edit.run_after_textinput(Editor_state, 'g')
-  check_eq(Editor_state.cursor1.line, 2, 'F - test_undo_insert_text/baseline/cursor:line')
-  check_eq(Editor_state.cursor1.pos, 5, 'F - test_undo_insert_text/baseline/cursor:pos')
-  check_nil(Editor_state.selection1.line, 'F - test_undo_insert_text/baseline/selection:line')
-  check_nil(Editor_state.selection1.pos, 'F - test_undo_insert_text/baseline/selection:pos')
-  local y = Editor_state.top
-  App.screen.check(y, 'abc', 'F - test_undo_insert_text/baseline/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'defg', 'F - test_undo_insert_text/baseline/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'xyz', 'F - test_undo_insert_text/baseline/screen:3')
-  -- undo
-  edit.run_after_keychord(Editor_state, 'C-z')
-  check_eq(Editor_state.cursor1.line, 2, 'F - test_undo_insert_text/cursor:line')
-  check_eq(Editor_state.cursor1.pos, 4, 'F - test_undo_insert_text/cursor:pos')
-  check_nil(Editor_state.selection1.line, 'F - test_undo_insert_text/selection:line')
-  check_nil(Editor_state.selection1.pos, 'F - test_undo_insert_text/selection:pos')
-  y = Editor_state.top
-  App.screen.check(y, 'abc', 'F - test_undo_insert_text/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'def', 'F - test_undo_insert_text/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'xyz', 'F - test_undo_insert_text/screen:3')
-end
-
-function test_undo_delete_text()
-  io.write('\ntest_undo_delete_text')
-  App.screen.init{width=120, height=60}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc', 'defg', 'xyz'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=2, pos=5}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  -- delete a character
-  edit.run_after_keychord(Editor_state, 'backspace')
-  check_eq(Editor_state.cursor1.line, 2, 'F - test_undo_delete_text/baseline/cursor:line')
-  check_eq(Editor_state.cursor1.pos, 4, 'F - test_undo_delete_text/baseline/cursor:pos')
-  check_nil(Editor_state.selection1.line, 'F - test_undo_delete_text/baseline/selection:line')
-  check_nil(Editor_state.selection1.pos, 'F - test_undo_delete_text/baseline/selection:pos')
-  local y = Editor_state.top
-  App.screen.check(y, 'abc', 'F - test_undo_delete_text/baseline/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'def', 'F - test_undo_delete_text/baseline/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'xyz', 'F - test_undo_delete_text/baseline/screen:3')
-  -- undo
---?   -- after undo, the backspaced key is selected
-  edit.run_after_keychord(Editor_state, 'C-z')
-  check_eq(Editor_state.cursor1.line, 2, 'F - test_undo_delete_text/cursor:line')
-  check_eq(Editor_state.cursor1.pos, 5, 'F - test_undo_delete_text/cursor:pos')
-  check_nil(Editor_state.selection1.line, 'F - test_undo_delete_text/selection:line')
-  check_nil(Editor_state.selection1.pos, 'F - test_undo_delete_text/selection:pos')
---?   check_eq(Editor_state.selection1.line, 2, 'F - test_undo_delete_text/selection:line')
---?   check_eq(Editor_state.selection1.pos, 4, 'F - test_undo_delete_text/selection:pos')
-  y = Editor_state.top
-  App.screen.check(y, 'abc', 'F - test_undo_delete_text/screen:1')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'defg', 'F - test_undo_delete_text/screen:2')
-  y = y + Editor_state.line_height
-  App.screen.check(y, 'xyz', 'F - test_undo_delete_text/screen:3')
-end
-
-function test_undo_restores_selection()
-  io.write('\ntest_undo_restores_selection')
-  -- display a line of text with some part selected
-  App.screen.init{width=75, height=80}
-  Editor_state = edit.initialize_test_state()
-  Editor_state.lines = load_array{'abc'}
-  Text.redraw_all(Editor_state)
-  Editor_state.cursor1 = {line=1, pos=1}
-  Editor_state.selection1 = {line=1, pos=2}
-  Editor_state.screen_top1 = {line=1, pos=1}
-  Editor_state.screen_bottom1 = {}
-  edit.draw(Editor_state)
-  -- delete selected text
-  edit.run_after_textinput(Editor_state, 'x')
-  check_eq(Editor_state.lines[1].data, 'xbc', 'F - test_undo_restores_selection/baseline')
-  check_nil(Editor_state.selection1.line, 'F - test_undo_restores_selection/baseline:selection')
-  -- undo
-  edit.run_after_keychord(Editor_state, 'C-z')
-  edit.run_after_keychord(Editor_state, 'C-z')
-  -- selection is restored
-  check_eq(Editor_state.selection1.line, 1, 'F - test_undo_restores_selection/line')
-  check_eq(Editor_state.selection1.pos, 2, 'F - test_undo_restores_selection/pos')
-end
-
 function test_search()
   io.write('\ntest_search')
   App.screen.init{width=120, height=60}
diff --git a/undo.lua b/undo.lua
deleted file mode 100644
index 912c949..0000000
--- a/undo.lua
+++ /dev/null
@@ -1,110 +0,0 @@
--- undo/redo by managing the sequence of events in the current session
--- based on https://github.com/akkartik/mu1/blob/master/edit/012-editor-undo.mu
-
--- Incredibly inefficient; we make a copy of lines on every single keystroke.
--- The hope here is that we're either editing small files or just reading large files.
--- TODO: highlight stuff inserted by any undo/redo operation
--- TODO: coalesce multiple similar operations
-
-function record_undo_event(State, data)
-  State.history[State.next_history] = data
-  State.next_history = State.next_history+1
-  for i=State.next_history,#State.history do
-    State.history[i] = nil
-  end
-end
-
-function undo_event(State)
-  if State.next_history > 1 then
---?     print('moving to history', State.next_history-1)
-    State.next_history = State.next_history-1
-    local result = State.history[State.next_history]
-    return result
-  end
-end
-
-function redo_event(State)
-  if State.next_history <= #State.history then
---?     print('restoring history', State.next_history+1)
-    local result = State.history[State.next_history]
-    State.next_history = State.next_history+1
-    return result
-  end
-end
-
--- Copy all relevant global state.
--- Make copies of objects; the rest of the app may mutate them in place, but undo requires immutable histories.
-function snapshot(State, s,e)
-  -- Snapshot everything by default, but subset if requested.
-  assert(s)
-  if e == nil then
-    e = s
-  end
-  assert(#State.lines > 0)
-  if s < 1 then s = 1 end
-  if s > #State.lines then s = #State.lines end
-  if e < 1 then e = 1 end
-  if e > #State.lines then e = #State.lines end
-  -- compare with App.initialize_globals
-  local event = {
-    screen_top=deepcopy(State.screen_top1),
-    selection=deepcopy(State.selection1),
-    cursor=deepcopy(State.cursor1),
-    lines={},
-    start_line=s,
-    end_line=e,
-    -- no filename; undo history is cleared when filename changes
-  }
-  -- deep copy lines without cached stuff like text fragments
-  for i=s,e do
-    local line = State.lines[i]
-    table.insert(event.lines, {data=line.data})
-  end
-  return event
-end
-
-function patch(lines, from, to)
---?   if #from.lines == 1 and #to.lines == 1 then
---?     assert(from.start_line == from.end_line)
---?     assert(to.start_line == to.end_line)
---?     assert(from.start_line == to.start_line)
---?     lines[from.start_line] = to.lines[1]
---?     return
---?   end
-  assert(from.start_line == to.start_line)
-  for i=from.end_line,from.start_line,-1 do
-    table.remove(lines, i)
-  end
-  assert(#to.lines == to.end_line-to.start_line+1)
-  for i=1,#to.lines do
-    table.insert(lines, to.start_line+i-1, to.lines[i])
-  end
-end
-
-function patch_placeholders(line_cache, from, to)
-  assert(from.start_line == to.start_line)
-  for i=from.end_line,from.start_line,-1 do
-    table.remove(line_cache, i)
-  end
-  assert(#to.lines == to.end_line-to.start_line+1)
-  for i=1,#to.lines do
-    table.insert(line_cache, to.start_line+i-1, {})
-  end
-end
-
--- https://stackoverflow.com/questions/640642/how-do-you-copy-a-lua-table-by-value/26367080#26367080
-function deepcopy(obj, seen)
-  if type(obj) ~= 'table' then return obj end
-  if seen and seen[obj] then return seen[obj] end
-  local s = seen or {}
-  local result = setmetatable({}, getmetatable(obj))
-  s[obj] = result
-  for k,v in pairs(obj) do
-    result[deepcopy(k, s)] = deepcopy(v, s)
-  end
-  return result
-end
-
-function minmax(a, b)
-  return math.min(a,b), math.max(a,b)
-end