vcl mainloop bits ...

Hi there,

        Am struggling to unwind the intent of the appended ;-) a little healthy
paranoia with the glib mainloop integration is sensible since small
changes there affect a ton of unexpected orderings in the code and ... -
anyhow ;-)

commit 21a9089aa4324ccbdc9e9ee3669e5fb524efd03c
Author: Pierre-Eric Pelloux-Prayer <pierre-eric@lanedo.com>
Date:   Fri Jul 5 14:17:46 2013 +0200

        The description seems to suggest that:

    gtk/unx: remove successive calls to g_main_context_iteration
    
    Replace the sequence:
...
        blocking call to g_main_context_iteration until first evt reveived.

    This allows more longer sleep period, when nothing is going on (verified
    with strace).

...

diff --git a/vcl/unx/gtk/app/gtkdata.cxx b/vcl/unx/gtk/app/gtkdata.cxx
index 6abb06b..5ff5a80 100644
--- a/vcl/unx/gtk/app/gtkdata.cxx
+++ b/vcl/unx/gtk/app/gtkdata.cxx
@@ -571,12 +571,10 @@ void GtkData::Yield( bool bWait, bool bHandleAllCurrentEvents )
             gboolean wasOneEvent = TRUE;
             while( nMaxEvents-- && wasOneEvent )
             {
-                wasOneEvent = g_main_context_iteration( NULL, FALSE );
+                wasOneEvent = g_main_context_iteration( NULL, bWait & !bWasEvent );
                 if( wasOneEvent )
                     bWasEvent = true;
             }
-            if( bWait && ! bWasEvent )
-                bWasEvent = g_main_context_iteration( NULL, TRUE ) != 0;
         }

        Of course - the old code was pretty odd and ugly - but I read the above
for the bWait == TRUE case - which I assume you're optimising as:

        while ( 1-- && TRUE )
        {
                wasOneEvent = g_main_context_iteration (NULL, bWait && FALSE );

        The first time around - right ? seems like that does a non-waiting run
through the main-loop as before.

        what somewhat concerns me is that in the case ofbHandleAllCurrentEvents
== FALSE and bWait == TRUE - we have a different behaviour - we don't
wait nMaxEvents == 0 now - and we bail out.

        Couldn't that create a busy loop ?

        Anyhow - thanks for being brave enough to touch this :-) the main-loop
logic clearly needs some love - and we -very- badly need some sensible
idle priorities system adding to VCL to get better quality rendering and
better work scheduling :-)

        ATB,

                Michael.

-- 
michael.meeks@suse.com  <><, Pseudo Engineer, itinerant idiot