bug#42406: Mouse-wheel scrolling can be flickering

[martin rudalics]

>> In redisplay_window we set
>>
>>     update_mode_line = (w->update_mode_line
>>                      || update_mode_lines
>>
>> where w is the window we redisplay because it got scrolled.  Later down
>> we have
>>
>>     if (update_mode_line
>>         && EQ (FRAME_SELECTED_WINDOW (f), window))
>>       {
>>         ...
>>         gui_consider_frame_title (w->frame);
>>
>> so we do update the frame title after the frame's selected window got
>> scrolled.  What am I missing?
>
> This, I think:
>
>    if (current_matrix_up_to_date_p
>        && (rc = try_cursor_movement (window, startp, &temp_scroll_step),
>      rc != CURSOR_MOVEMENT_CANNOT_BE_USED))
>      {
>        switch (rc)
>    {
>    case CURSOR_MOVEMENT_SUCCESS:
>      used_current_matrix_p = true;
>      goto done;
>
> IOW, we might think that nothing needs to be updated except perhaps
> the cursor position, and then fail to update the frame's title.

Just to make sure I understand your argument correctly: With my xdisp.c

  update_mode_line = (w->update_mode_line is on line 18065

  case CURSOR_MOVEMENT_SUCCESS: is on line 18458

  done: is on line 18929

  if (update_mode_line is on line 18975

  gui_consider_frame_title (w->frame); is on line 19020

so I can't see why a CURSOR_MOVEMENT_SUCCESS could bypass
gui_consider_frame_title.

martin