[PyKDE] QCanvas.advance() from other than the GUI thread

[Miller, Douglas]

On SuSE 8.0 with Qt at 3.0.3, PyQt/SIP at 3.4 the following works from a thread OTHER than the GUI thread:

 

    def doAdvance(self, parent, tyme):
        #lock GUI resources with the Qt Library Mutex
        qApp.lock()
        parent.childCanvas.advance()
        qApp.unlock()
        tyme = tyme + 1/float(ADVANCE_RATE_DIVISOR)     #modify time by advance rate
        #enter next absolute time event
        self.schedule.enterabs(tyme, 1, self.doAdvance, (parent, tyme)) 

 

Also, on Red 9.0 with Qt at 3.1.1, PyQt/SIP at 3.5 the above also works

 

BUT, on SuSE 8.2 with Qt at 3.1.1, PyQt/SIP at 3.8 the above does NOT work.

 

When my application is executed I get the following errors:

 

Xlib: unexpected async reply .....

 

OR something like

 

X Error: BadPixmap (invalid Pixmap parameter) 4
  Major opcode:  56
  Minor opcode:  0
  Resource id:  0x50046

X Error: BadLength (poly request too large or internal Xlib length error) 16
  Major opcode:  75
  Minor opcode:  0
  Resource id:  0x0

 

These error messages disappear when 'parent.childCanvas.advance()' is commented out.

I know this has something to do with threading, because the mail Qt mail archive has postings with these kinds of errors.

 

The real question that I have is what happened between PyQt 3.5 and PyQt 3.8 that this is now a problem when it was not before?

What can be done about this problem?

 

NOTE: If, in the GUI thread, I use QCanvas.setAdvancePeriod () or if I use a QTimer to call QCanvas.advance() on a regular basis, object motion on the canvas slows when the application is under heavy utilization.  The above construct has been the only way that I could keep object motion constant.

 

Thanks for any help.