[Qt-interest] Qt4.4.3 paintEvent thread-safe

[Prasanta Sadhukhan]

Andreas Pakulat wrote:
> On 22.12.08 14:43:42, Prasanta Sadhukhan wrote:
>   
>> which got solved when I introduced a mutex lock and unlock inside my 
>> PaintEvent function, like this
>>
>> void QtWindow::paintEvent(QPaintEvent *event)
>> {
>>  
>>     AWT_QT_LOCK;
>>     QPainter p(this);
>>     QPoint pt(0,0);
>>     p.drawImage(pt, *QtImageDescPool[0].offscrSurface);
>>     
>
> I guess this array is shared by both threads, the Qt-painting thread and
> the one that paints onto the offscreen image?
Yes
>  If so, thats why you need the
> lock, which probably causes the slowdown. There are only 2 solutions here:
>
> a) provide a completely copy of the offscreen image to the qt-painting
> thread instead of using a global array (for example by using a custom Qt
> event that carries the QImage)
>   
Can you please elaborate on this solution?

Thanks
Prasanta
> b) merge the code to have just 1 thread in the application.
>
> Andreas
>
>