function source.mouse_wheel_move(dx,dy)
  Cursor_time = 0  -- ensure cursor is visible immediately after it moves
  if Focus == 'edit' then
    return edit.mouse_wheel_move(Editor_state, dx,dy)
  else
    return log_browser.mouse_wheel_move(Log_browser_state, dx,dy)
  end
end

function run.mouse_wheel_move(dx,dy)
  Cursor_time = 0  -- ensure cursor is visible immediately after it moves
  return edit.mouse_wheel_move(Editor_state, dx,dy)
end

  else
    assert(false, 'unknown app "'..Current_app..'"')
  end
end
function App.wheelmoved(dx,dy)
  if Current_app == 'run' then
    if run.mouse_wheel_move then run.mouse_wheel_move(dx,dy) end
  elseif Current_app == 'source' then
    if source.mouse_wheel_move then source.mouse_wheel_move(dx,dy) end

  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}
    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}
    for i=1,math.floor(-dy) do
      Text.down(State)
    end