[PyQt] processEvents on QlistWidget operations does nothing

Andreas Pakulat apaku at gmx.de
Sun Jan 27 17:32:08 GMT 2008

On 27.01.08 16:45:36, P. Mathé wrote:
> I am sending you this message, originally sent to the PyQt mailing list, as it seems, according to Phil's answer that the problem lies within Qt.
> As suggested by Phil, I changed the program to make the urllib call from within a different thread, but, if it partially solves the problem, it repaces one line of code by 
> more than fifty, makes the code almost unreadable, and disconnect the QListWidget from the QProgressBar updates. (the new code is at your disposal).
> My point I that I just want that QListWidget works as expected , i.e. that when I say "addItem(...)", I see the item in the UI, now, not later , who knows when.

Uhm, the QListWidget does have the item immediately, however the
repainting only happens on the next run of the event loop. Calling
QApplication::processEvents is known to break in certain situations, any
longer-taking operation that shouldn't block the UI simply belongs into
a separate thread or process. Its usage is specifically for those who
know what they're doing.

Most of the time you're far better off writing a short QThread subclass
that does the "hard work" and sends either a custom event or simply a
signal using Qt::QueuedConnection.

Last but not least: If you want Qt behaviour to be changed, you need to
write a bugreport to Trolltech.


Don't hate yourself in the morning -- sleep till noon.

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