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Variant of [the Mu programming environment](../edit) that runs just the sandbox.

Suitable for people who want to run their favorite terminal-based editor with
Mu. Just run editor and sandbox inside split panes atop tmux. For example,
here's Mu running alongside vim:

<img alt='tmux+vim example' src='../html/tmux-vim-sandbox.png'>

To set this up:

  a) copy the lines in tmux.conf into `$HOME/.tmux.conf`.

  b) copy the file `mu_run` somewhere in your `$PATH`.

Now when you start tmux, split it into two vertical panes, run `./mu sandbox`
on the right pane and your editor on the left. You should be able to hit F4 in
either side to run the sandbox.

Known issues: you have to explicitly save inside your editor before hitting
F4, unlike with `./mu edit`.

---

Appendix: keyboard shortcuts

  _moving_
  - `ctrl-a` or `home`: move cursor to start of line
  - `ctrl-e` or `end`: move cursor to end of line

  _modifying text_
  - `ctrl-k`: delete text from cursor to end of line
  - `ctrl-u`: delete text from start of line until just before cursor
  - `ctrl-/`: comment/uncomment current line (using a special leader to ignore real comments https://www.reddit.com/r/vim/comments/4ootmz/_/d4ehmql)
0'>550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626
-- some constants people might like to tweak
Text_color = {r=0, g=0, b=0}
Cursor_color = {r=1, g=0, b=0}
Stroke_color = {r=0, g=0, b=0}
Current_stroke_color = {r=0.7, g=0.7, b=0.7}  -- in process of being drawn
Current_name_background_color = {r=1, g=0, b=0, a=0.1}  -- name currently being edited
Focus_stroke_color = {r=1, g=0, b=0}  -- what mouse is hovering over
Highlight_color = {r=0.7, g=0.7, b=0.9}  -- selected text
Icon_color = {r=0.7, g=0.7, b=0.7}  -- color of current mode icon in drawings
Help_color = {r=0, g=0.5, b=0}
Help_background_color = {r=0, g=0.5, b=0, a=0.1}

Margin_top = 15
Margin_left = 25
Margin_right = 25

Drawing_padding_top = 10
Drawing_padding_bottom = 10
Drawing_padding_height = Drawing_padding_top + Drawing_padding_bottom

Same_point_distance = 4  -- pixel distance at which two points are considered the same

edit = {}

-- run in both tests and a real run
function edit.initialize_state(top, left, right, font_height, line_height)  -- currently always draws to bottom of screen
  local result = {
    -- a line is either text or a drawing
    -- a text is a table with:
    --    mode = 'text',
    --    string data,
    -- a drawing is a table with:
    --    mode = 'drawing'
    --    a (y) coord in pixels (updated while painting screen),
    --    a (h)eight,
    --    an array of points, and
    --    an array of shapes
    -- a shape is a table containing:
    --    a mode
    --    an array points for mode 'freehand' (raw x,y coords; freehand drawings don't pollute the points array of a drawing)
    --    an array vertices for mode 'polygon', 'rectangle', 'square'
    --    p1, p2 for mode 'line'
    --    center, radius for mode 'circle'
    --    center, radius, start_angle, end_angle for mode 'arc'
    -- Unless otherwise specified, coord fields are normalized; a drawing is always 256 units wide
    -- The field names are carefully chosen so that switching modes in midstream
    -- remembers previously entered points where that makes sense.
    lines = {{mode='text', data=''}},  -- array of lines

    -- Lines can be too long to fit on screen, in which case they _wrap_ into
    -- multiple _screen lines_.

    -- rendering wrapped text lines needs some additional short-lived data per line:
    --   startpos, the index of data the line starts rendering from, can only be >1 for topmost line on screen
    --   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
    line_cache = {},

    -- Given wrapping, any potential location for the text cursor can be described in two ways:
    -- * schema 1: As a combination of line index and position within a line (in utf8 codepoint units)
    -- * schema 2: As a combination of line index, screen line index within the line, and a position within the screen line.
    --
    -- Most of the time we'll only persist positions in schema 1, translating to
    -- schema 2 when that's convenient.
    --
    -- Make sure these coordinates are never aliased, so that changing one causes
    -- action at a distance.
    screen_top1 = {line=1, pos=1},  -- position of start of screen line at top of screen
    cursor1 = {line=1, pos=1},  -- position of cursor
    screen_bottom1 = {line=1, pos=1},  -- position of start of screen line at bottom of screen

    selection1 = {},
    -- some extra state to compute selection between mouse press and release
    old_cursor1 = nil,
    old_selection1 = nil,
    mousepress_shift = nil,

    -- cursor coordinates in pixels
    cursor_x = 0,
    cursor_y = 0,

    current_drawing_mode = 'line',
    previous_drawing_mode = nil,  -- extra state for some ephemeral modes like moving/deleting/naming points

    font_height = font_height,
    line_height = line_height,

    top = top,
    left = math.floor(left),
    right = math.floor(right),
    width = right-left,

    filename = love.filesystem.getSourceBaseDirectory()..'/lines.txt',  -- '/' should work even on Windows
    next_save = nil,

    -- undo
    history = {},
    next_history = 1,

    -- search
    search_term = nil,
    search_backup = nil,  -- stuff to restore when cancelling search
  }
  return result
end  -- App.initialize_state

function edit.check_locs(State)
  -- if State is inconsistent (i.e. file changed by some other program),
  --   throw away all cursor state entirely
  if edit.invalid1(State, State.screen_top1)
      or edit.invalid_cursor1(State)
      or not edit.cursor_on_text(State)
      or not Text.le1(State.screen_top1, State.cursor1) then
    State.screen_top1 = {line=1, pos=1}
    State.cursor1 = {line=1, pos=1}
    edit.put_cursor_on_next_text_line(State)
  end
end

function edit.invalid1(State, loc1)
  if loc1.line > #State.lines then return true end
  local l = State.lines[loc1.line]
  if l.mode ~= 'text' then return false end  -- pos is irrelevant to validity for a drawing line
  return loc1.pos > #State.lines[loc1.line].data
end

-- cursor loc in particular differs from other locs in one way:
-- pos might occur just after end of line
function edit.invalid_cursor1(State)
  local cursor1 = State.cursor1
  if cursor1.line > #State.lines then return true end
  local l = State.lines[cursor1.line]
  if l.mode ~= 'text' then return false end  -- pos is irrelevant to validity for a drawing line
  return cursor1.pos > #State.lines[cursor1.line].data + 1
end

function edit.cursor_on_text(State)
  return State.cursor1.line <= #State.lines
      and State.lines[State.cursor1.line].mode == 'text'
end

function edit.put_cursor_on_next_text_line(State)
  while true do
    if State.cursor1.line >= #State.lines then
      break
    end
    if State.lines[State.cursor1.line].mode == 'text' then
      break
    end
    State.cursor1.line = State.cursor1.line+1
    State.cursor1.pos = 1
  end
end

-- return y drawn until
function edit.draw(State)
  State.button_handlers = {}
  App.color(Text_color)
  if #State.lines ~= #State.line_cache then
    print(('line_cache is out of date; %d when it should be %d'):format(#State.line_cache, #State.lines))
    assert(false)
  end
  if not Text.le1(State.screen_top1, State.cursor1) then
    print(State.screen_top1.line, State.screen_top1.pos, State.cursor1.line, State.cursor1.pos)
    assert(false)
  end
  State.cursor_x = nil
  State.cursor_y = nil
  local y = State.top
  local screen_bottom1 = {line=nil, pos=nil}
--?   print('== draw')
  for line_index = State.screen_top1.line,#State.lines do
    local line = State.lines[line_index]
--?     print('draw:', y, line_index, line)
    if y + State.line_height > App.screen.height then break end
    screen_bottom1.line = line_index
    if line.mode == 'text' then
--?       print('text.draw', y, line_index)
      local startpos = 1
      if line_index == State.screen_top1.line then
        startpos = State.screen_top1.pos
      end
      if line.data == '' then
        -- button to insert new drawing
        button(State, 'draw', {x=State.left-Margin_left+4, y=y+4, w=12,h=12, bg={r=1,g=1,b=0},
          icon = icon.insert_drawing,
          onpress1 = function()
                       Drawing.before = snapshot(State, line_index-1, line_index)
                       table.insert(State.lines, line_index, {mode='drawing', y=y, h=256/2, points={}, shapes={}, pending={}})
                       table.insert(State.line_cache, line_index, {})
                       if State.cursor1.line >= line_index then
                         State.cursor1.line = State.cursor1.line+1
                       end
                       schedule_save(State)
                       record_undo_event(State, {before=Drawing.before, after=snapshot(State, line_index-1, line_index+1)})
                     end,
        })
      end
      y, screen_bottom1.pos = Text.draw(State, line_index, y, startpos)
--?       print('=> y', y)
    elseif line.mode == 'drawing' then
      y = y+Drawing_padding_top
      Drawing.draw(State, line_index, y)
      y = y + Drawing.pixels(line.h, State.width) + Drawing_padding_bottom
    else
      print(line.mode)
      assert(false)
    end
  end
  State.screen_bottom1 = screen_bottom1
  if State.search_term then
    Text.draw_search_bar(State)
  end
  return y
end

function edit.update(State, dt)
  Drawing.update(State, dt)
  if State.next_save and State.next_save < Current_time then
    save_to_disk(State)
    State.next_save = nil
  end
end

function schedule_save(State)
  if State.next_save == nil then
    State.next_save = Current_time + 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)
    -- give some time for the OS to flush everything to disk
    love.timer.sleep(0.1)
  end
end

function edit.mouse_press(State, x,y, mouse_button)
  if State.search_term then return end
--?   print_and_log(('edit.mouse_press: cursor at %d,%d'):format(State.cursor1.line, State.cursor1.pos))
  if mouse_press_consumed_by_any_button_handler(State, x,y, mouse_button) then
    -- press on a button and it returned 'true' to short-circuit
    return
  end

  if y < State.top then
    State.old_cursor1 = State.cursor1
    State.old_selection1 = State.selection1
    State.mousepress_shift = App.shift_down()
    State.selection1 = {
        line=State.screen_top1.line,
        pos=State.screen_top1.pos,
    }
    return
  end

  for line_index,line in ipairs(State.lines) do
    if line.mode == 'text' then
      if Text.in_line(State, line_index, x,y) then
        -- delicate dance between cursor, selection and old cursor/selection
        -- scenarios:
        --  regular press+release: sets cursor, clears selection
        --  shift press+release:
        --    sets selection to old cursor if not set otherwise leaves it untouched
        --    sets cursor
        --  press and hold to start a selection: sets selection on press, cursor on release
        --  press and hold, then press shift: ignore shift
        --    i.e. mouse_release should never look at shift state
--?         print_and_log(('edit.mouse_press: in line %d'):format(line_index))
        State.old_cursor1 = State.cursor1
        State.old_selection1 = State.selection1
        State.mousepress_shift = App.shift_down()
        State.selection1 = {
            line=line_index,
            pos=Text.to_pos_on_line(State, line_index, x, y),
        }
        return
      end
    elseif line.mode == 'drawing' then
      local line_cache = State.line_cache[line_index]
      if Drawing.in_drawing(line, line_cache, x, y, State.left,State.right) then
        State.lines.current_drawing_index = line_index
        State.lines.current_drawing = line
        Drawing.before = snapshot(State, line_index)
        Drawing.mouse_press(State, line_index, x,y, mouse_button)
        return
      end
    end
  end

  -- still here? mouse press is below all screen lines
  State.old_cursor1 = State.cursor1
  State.old_selection1 = State.selection1
  State.mousepress_shift = App.shift_down()
  State.selection1 = {
      line=State.screen_bottom1.line,
      pos=Text.pos_at_end_of_screen_line(State, State.screen_bottom1),
  }
end

function edit.mouse_release(State, x,y, mouse_button)
  if State.search_term then return end
--?   print_and_log(('edit.mouse_release: cursor at %d,%d'):format(State.cursor1.line, State.cursor1.pos))
  if State.lines.current_drawing then
    Drawing.mouse_release(State, x,y, mouse_button)
    schedule_save(State)
    if Drawing.before then
      record_undo_event(State, {before=Drawing.before, after=snapshot(State, State.lines.current_drawing_index)})
      Drawing.before = nil
    end
  else
--?     print_and_log('edit.mouse_release: no current drawing')
    if y < State.top then
      State.cursor1 = {line=State.screen_top1.line, pos=State.screen_top1.pos}
      edit.clean_up_mouse_press(State)
      return
    end

    for line_index,line in ipairs(State.lines) do
      if line.mode == 'text' then
        if Text.in_line(State, line_index, x,y) then
--?           print_and_log(('edit.mouse_release: in line %d'):format(line_index))
          State.cursor1 = {
              line=line_index,
              pos=Text.to_pos_on_line(State, line_index, x, y),
          }
--?           print_and_log(('edit.mouse_release: cursor now %d,%d'):format(State.cursor1.line, State.cursor1.pos))
          edit.clean_up_mouse_press(State)
          return
        end
      end
    end

    -- still here? mouse release is below all screen lines
    State.cursor1.line, State.cursor1.pos = State.screen_bottom1.line, Text.pos_at_end_of_screen_line(State, State.screen_bottom1)
    edit.clean_up_mouse_press(State)
--?     print_and_log(('edit.mouse_release: finally selection %s,%s cursor %d,%d'):format(tostring(State.selection1.line), tostring(State.selection1.pos), State.cursor1.line, State.cursor1.pos))
  end
end

function edit.clean_up_mouse_press(State)
  if State.mousepress_shift then
    if State.old_selection1.line == nil then
      State.selection1 = State.old_cursor1
    else
      State.selection1 = State.old_selection1
    end
  end
  State.old_cursor1, State.old_selection1, State.mousepress_shift = nil
  if eq(State.cursor1, State.selection1) then
    State.selection1 = {}
  end
end

function edit.mouse_wheel_move(State, dx,dy)
  if dy > 0 then
    State.cursor1 = {line=State.screen_top1.line, pos=State.screen_top1.pos}
    edit.put_cursor_on_next_text_line(State)
    for i=1,math.floor(dy) do
      Text.up(State)
    end
  elseif dy < 0 then
    State.cursor1 = {line=State.screen_bottom1.line, pos=State.screen_bottom1.pos}
    edit.put_cursor_on_next_text_line(State)
    for i=1,math.floor(-dy) do
      Text.down(State)
    end
  end
end

function edit.text_input(State, t)
--?   print('text input', t)
  if State.search_term then
    State.search_term = State.search_term..t
    Text.search_next(State)
  elseif State.lines.current_drawing and State.current_drawing_mode == 'name' then
    local before = snapshot(State, State.lines.current_drawing_index)
    local drawing = State.lines.current_drawing
    local p = drawing.points[drawing.pending.target_point]
    p.name = p.name..t
    record_undo_event(State, {before=before, after=snapshot(State, State.lines.current_drawing_index)})
  else
    local drawing_index, drawing = Drawing.current_drawing(State)
    if drawing_index == nil then
      for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
      Text.text_input(State, t)
    end
  end
  schedule_save(State)
end

function edit.keychord_press(State, chord, key)
  if State.selection1.line and
      not State.lines.current_drawing and
      -- printable character created using shift key => delete selection
      -- (we're not creating any ctrl-shift- or alt-shift- combinations using regular/printable keys)
      (not App.shift_down() or utf8.len(key) == 1) and
      chord ~= 'C-a' and chord ~= 'C-c' and chord ~= 'C-x' and chord ~= 'backspace' and chord ~= 'delete' and chord ~= 'C-z' and chord ~= 'C-y' and not App.is_cursor_movement(chord) then
    Text.delete_selection(State, State.left, State.right)
  end
  if State.search_term then
    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
    if chord == 'escape' then
      State.search_term = nil
      State.cursor1 = State.search_backup.cursor
      State.screen_top1 = State.search_backup.screen_top
      State.search_backup = nil
      Text.redraw_all(State)  -- if we're scrolling, reclaim all fragments to avoid memory leaks
    elseif chord == 'return' then
      State.search_term = nil
      State.search_backup = nil
    elseif chord == 'backspace' then
      local len = utf8.len(State.search_term)
      local byte_offset = Text.offset(State.search_term, len)
      State.search_term = string.sub(State.search_term, 1, byte_offset-1)
    elseif chord == 'down' then
      State.cursor1.pos = State.cursor1.pos+1
      Text.search_next(State)
    elseif chord == 'up' then
      Text.search_previous(State)
    end
    return
  elseif chord == 'C-f' then
    State.search_term = ''
    State.search_backup = {
      cursor={line=State.cursor1.line, pos=State.cursor1.pos},
      screen_top={line=State.screen_top1.line, pos=State.screen_top1.pos},
    }
  -- zoom
  elseif chord == 'C-=' then
    edit.update_font_settings(State, State.font_height+2)
    Text.redraw_all(State)
  elseif chord == 'C--' then
    if State.font_height > 2 then
      edit.update_font_settings(State, State.font_height-2)
      Text.redraw_all(State)
    end
  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)
      -- invalidate various cached bits of lines
      State.lines.current_drawing = nil
      -- 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)
      -- invalidate various cached bits of lines
      State.lines.current_drawing = nil
      -- if we're scrolling, reclaim all fragments to avoid memory leaks
      Text.redraw_all(State)
      schedule_save(State)
    end
  -- clipboard
  elseif chord == 'C-a' then
    State.selection1 = {line=1, pos=1}
    State.cursor1 = {line=#State.lines, pos=utf8.len(State.lines[#State.lines].data)+1}
  elseif chord == 'C-c' then
    local s = Text.selection(State)
    if s then
      App.set_clipboard(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.set_clipboard(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.get_clipboard()
    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 drawing or text
  elseif App.mouse_down(1) or chord:sub(1,2) == 'C-' then
    -- DON'T reset line_cache.starty here
    local drawing_index, drawing = Drawing.current_drawing(State)
    if drawing_index then
      local before = snapshot(State, drawing_index)
      Drawing.keychord_press(State, chord)
      record_undo_event(State, {before=before, after=snapshot(State, drawing_index)})
      schedule_save(State)
    end
  elseif chord == 'escape' and not App.mouse_down(1) then
    for _,line in ipairs(State.lines) do
      if line.mode == 'drawing' then
        line.show_help = false
      end
    end
  elseif State.lines.current_drawing and State.current_drawing_mode == 'name' then
    if chord == 'return' then
      State.current_drawing_mode = State.previous_drawing_mode
      State.previous_drawing_mode = nil
    else
      local before = snapshot(State, State.lines.current_drawing_index)
      local drawing = State.lines.current_drawing
      local p = drawing.points[drawing.pending.target_point]
      if chord == 'escape' then
        p.name = nil
        record_undo_event(State, {before=before, after=snapshot(State, State.lines.current_drawing_index)})
      elseif chord == 'backspace' then
        local len = utf8.len(p.name)
        if len > 0 then
          local byte_offset = Text.offset(p.name, len-1)
          if len == 1 then byte_offset = 0 end
          p.name = string.sub(p.name, 1, byte_offset)
          record_undo_event(State, {before=before, after=snapshot(State, State.lines.current_drawing_index)})
        end
      end
    end
    schedule_save(State)
  else
    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
    Text.keychord_press(State, chord)
  end
end

function edit.key_release(State, key, scancode)
end

function edit.update_font_settings(State, font_height)
  State.font_height = font_height
  love.graphics.setFont(love.graphics.newFont(State.font_height))
  State.line_height = math.floor(font_height*1.3)
end

--== some methods for tests

-- Insulate tests from some key globals so I don't have to change the vast
-- majority of tests when they're modified for the real app.
Test_margin_left = 25
Test_margin_right = 0

function edit.initialize_test_state()
  -- if you change these values, tests will start failing
  return edit.initialize_state(
      15,  -- top margin
      Test_margin_left,
      App.screen.width - Test_margin_right,
      14,  -- font height assuming default LÖVE font
      15)  -- line height
end

-- all text_input events are also keypresses
-- TODO: handle chords of multiple keys
function edit.run_after_text_input(State, t)
  edit.keychord_press(State, t)
  edit.text_input(State, t)
  edit.key_release(State, t)
  App.screen.contents = {}
  edit.update(State, 0)
  edit.draw(State)
end

-- not all keys are text_input
function edit.run_after_keychord(State, chord)
  edit.keychord_press(State, chord)
  edit.key_release(State, chord)
  App.screen.contents = {}
  edit.update(State, 0)
  edit.draw(State)
end

function edit.run_after_mouse_click(State, x,y, mouse_button)
  App.fake_mouse_press(x,y, mouse_button)
  edit.mouse_press(State, x,y, mouse_button)
  App.fake_mouse_release(x,y, mouse_button)
  edit.mouse_release(State, x,y, mouse_button)
  App.screen.contents = {}
  edit.update(State, 0)
  edit.draw(State)
end

function edit.run_after_mouse_press(State, x,y, mouse_button)
  App.fake_mouse_press(x,y, mouse_button)
  edit.mouse_press(State, x,y, mouse_button)
  App.screen.contents = {}
  edit.update(State, 0)
  edit.draw(State)
end

function edit.run_after_mouse_release(State, x,y, mouse_button)
  App.fake_mouse_release(x,y, mouse_button)
  edit.mouse_release(State, x,y, mouse_button)
  App.screen.contents = {}
  edit.update(State, 0)
  edit.draw(State)
end