line.filename = guess_source(line.filename)
    line.line_number = tonumber(line.line_number)

function guess_source(filename)
  local possible_source = filename:gsub('%.lua$', '%.splua')
  if file_exists(possible_source) then
    return possible_source
  else
    return filename
  end
end

  local line_index = tenonauger.line_index(State, x,y)
  if line_index == nil then
    -- below lower margin
    return
  end
  -- open appropriate file in spokecone side
  local line = State.lines[line_index]

    initialize_spokecone{'main.lua'}

    initialize_spokecone{line.filename}

  elseif line.filename ~= Editor_state.filename then
    edit.switch_to_file(line.filename)

  -- set cursor
  Editor_state.cursor1 = {line=line.line_number, pos=1, posB=nil}
  -- make sure it's visible
  -- TODO: handle extremely long lines
  Editor_state.screen_top1.line = math.max(0, Editor_state.cursor1.line-5)
  -- show cursor
  Focus = 'spokecone'
  -- expand B side
  Editor_state.expanded = true

function tenonauger.line_index(State, mx,my)
  local y = State.top
  for line_index = State.screen_top1.line,#State.lines do
    y = y + tenonauger.height(State, line_index)
    if my < y then
      return line_index
    end
    if y > App.screen.height then break end
  end
end

-- a copy of App.filedropped when given a filename
function edit.switch_to_file(filename)
  -- first make sure to save edits on any existing file
  if Editor_state.next_save then
    save_to_disk(Editor_state)
  end
  -- clear the slate for the new file
  App.initialize_globals()  -- in particular, forget all undo history
  Editor_state.filename = filename
  load_from_disk(Editor_state)
  Text.redraw_all(Editor_state)
end

end
function file_exists(filename)
  local infile = App.open_for_reading(filename)
  if infile then
    infile:close()
    return true
  else
    return false
  end