[Freeciv-Dev] Re: (PR#3424) New flush code

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

Raimar Falke wrote:
> On Tue, Feb 25, 2003 at 11:51:58AM -0800, Jason Short wrote:
> 
>>>>>What does this list tell me? You said above that there are two times
>>>>>when flush is called: after the network (easy to implement) and during
>>>>>animation (we have animation for unit combat, unit movement and
>>>>>mushroom). So what is the reason for this list?
>>>>
>>>>No, the two times are:
>>>>
>>>>- Before we hand control back to the GUI main event loop.
>>>>- Before any animation.
>>>>
>>>>After the network code is only one case of #1.  For instance, when the 
>>>>user clicks a mouse to recenter the mapview, we call 
>>>>center_tile_mapcanvas and then we have to flush_dirty (except in gtk2). 
>>>> There are about 6 different cases where this type of thing is done 
>>>
>>>>from the GUI code.
>>>
>>>>So, the long and complicated list traces the callers of 
>>>>dirty_rect/dirty_all back toward the GUI main event loop.  At some point 
>>>>in between the two, there needs to be a call to flush_dirty.  You can 
>>>>verify that this is always the case.
>>>
>>>
>>>This sounds cumbersome and error-prone. Can't we put a call to
>>>gui_callback_finished in these callbacks which are called by the GUI?
>>
>>It probably will be cumbersome and error-prone, unfortunately.
>>
>>I don't quite understand your suggestion.  
> 
> 
>>You want every GUI callback to call gui_callback_finished when it's
>>done?
> 
> 
> Yes.

This seems horrendously inefficient, and a huge amount of work.  How 
many GUI callbacks are there?  Dozens?  Hundreds?  Compare this to the 
difficulty of adding 6 new flush_dirty calls.

> I think you brought this up and I now think it is a good idea: calling
> gui_callback_finished after each event. For this we have to break up
> the main loop. This is possible for:
>  - xaw: http://www.xfree86.org/4.2.0/XtAppNextEvent.3.html
>  - gtk: 
> http://developer.gnome.org/doc/API/gtk/gtk-general.html#GTK-MAIN-ITERATION
>  - gtk2: 
> http://developer.gnome.org/doc/API/2.0/gtk/gtk-General.html#gtk-main-iteration
> 
> sdl, win32 and mui already have to loop broken up in the current
> source code.

I don't understand what you're saying.  You want to break up the GUI's 
main event loop, replacing gtk_main() with something like

   while (!done) {
     gtk_main_iteration();
     flush_dirty();
   }

?  What if flush_dirty() itself generates a new GTK/GDK event?  This is 
again hideously expensive, and quite error-prone.

Or are you saying to break up the network loop by adding

   flush_dirty();
   while (gtk_events_pending()) {
     gtk_main_iteration();
   }

to be called every now and then?  This is also hideously expensive (the 
efficiency of the network operations is because they're done in 
batches), and even more error-prone then the previous suggestions since 
the network code is not re-entrant.

jason