[PATCH] Flicker less drawing

[REGAT-BARREL Aurelien]

Hi,
In file qwidget_win.cpp, in function
    void QWidget::repaint( int x, int y, int w, int h, bool erase )
lines 1547-1548
    QPaintEvent e( r, erase );
    if ( r != rect() )
        qt_set_paintevent_clipping( this, r );
 -> if ( erase )
 ->     this->erase( x, y, w, h );
    QApplication::sendEvent( this, &e );

If erasing is needed, it is done with erase(). I dont know where but it seems to be done a second time in response to the QPaintEvent raised. So I removed this 2 lines:
    if ( erase )
        this->erase( x, y, w, h );
and it removed the flickering I saw on the application I am testing. 
 
In file qapplication_win.cpp, lines 5653 & 5705, QWidget window class style is:
 
wcx.style = CS_DBLCLKS | CS_HREDRAW | CS_VREDRAW;
 
I always hated CS_HREDRAW and CS_VREDRAW styles. They cause entire window redrawing => background erasing + redrawing, which causes flickering. I removed this 2 styles. But, if the window size grows, then painting is needed.
So I modified
    QETWidget::translateConfigEvent
line 4831:
  if ( isVisible() ) {
        QResizeEvent e( newSize, oldSize );
        QApplication::sendSpontaneousEvent( this, &e );
  
  ->     this->repaint();
    } else {
        QResizeEvent * e = new QResizeEvent( newSize, oldSize );
        QApplication::postEvent( this, e );
    }                        

I added the repaint() call.
 
After that, there is less flickering. This is also true with the dirview example. But more testing is needed.
There is something strange : if you resize the window backwards  / forwards horizontally OR vertically, it doesn't flicker. It you resize both horizontally and vertically (bottom right corner), it does. I think it is because the 2 resize events are not merged, but 2 events = 2 repaint() are received / called very shortly. I tried to batch the repaint() call with InvalidateRect / postEvent(), but it does nothing. But it is the same behaviour with Qt 2.3 NC. So, if the patch is approved, maybe the bug "[ 1060157 ] Unnecessary flicker during repaint" could be considered corrected.
 
Here are the diff output from my local CVS copy:
-----------------------------------8<----------------------------------------------
diff -r1.1.2.30.2.23 qapplication_win.cpp
4831a4832,4833
> 
>                 this->repaint();
4835c4837
<             }
---
>             }                        
5653c5655
<     wcx.style = CS_DBLCLKS | CS_HREDRAW | CS_VREDRAW;
---
>     wcx.style = CS_DBLCLKS; // | CS_HREDRAW | CS_VREDRAW;
5705c5707
<     wcx.style = CS_DBLCLKS | CS_HREDRAW | CS_VREDRAW;
---
>     wcx.style = CS_DBLCLKS; // | CS_HREDRAW | CS_VREDRAW;
-----------------------------------8<----------------------------------------------
diff -r1.1.2.15.2.14 qwidget_win.cpp
1547,1548c1547,1548
<         if ( erase )
<             this->erase( x, y, w, h );
---
>         //if ( erase )
>         //    this->erase( x, y, w, h );
-----------------------------------8<----------------------------------------------
 
Regards.


Aurelien REGAT-BARREL 




		
---------------------------------
 Découvrez le nouveau Yahoo! Mail : 250 Mo d'espace de stockage pour vos mails !
Créez votre Yahoo! Mail

  Avec Yahoo! faites un don et soutenez le Téléthon !
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.kde.org/pipermail/kde-cygwin/attachments/20041215/4b0a03a0/attachment.html