Re: An issue with Qt styling and/or threads?

[Bernhard Schuster <schuster bernhard googlemail com>]

What as in a Qt 4.x to 4.y version change that Qt Pixmaps could only
be used in the UI thread, and no other thread. This can be considered
a bug. If you wrote the code I suggest you to use QImage which can be
used anywhere and convert it on the fly to QPixmap, right where you
need it to render (not a perfect solution, but the only I know of
right now).

Regards

Bernhard Schuster



2012/2/17 James Tappin <jtappin gmail com>:
> I have a problem running a Gtk program when using the "Qt" style as
> supplied via gtk-qt-engine and kde-config-gtk-style.
>
> The program is a fairly heavy duty computation that uses openmp for
> parallel computation and has a gtk progress monitor (which is updated
> from within a "critical" section so it can never be accessed by more
> than one thread at a time). When the "Qt" style is selected, the
> progress bars (gtk_progress_bar) are corrupted and the errors below
> are displayed repeatedly:
>
> (th_run:2015): Gdk-CRITICAL **: gdk_pixmap_foreign_new_for_display:
> assertion `(anid != 0)' failed
>
> (th_run:2015): Gdk-CRITICAL **: gdk_draw_drawable: assertion
> `GDK_IS_DRAWABLE (src)' failed
>
> (th_run:2015): GLib-GObject-CRITICAL **: g_object_unref: assertion
> `G_IS_OBJECT (object)' failed
> QPixmap: It is not safe to use pixmaps outside the GUI thread
> QPixmap: It is not safe to use pixmaps outside the GUI thread
> QPainter::begin: Paint device returned engine == 0, type: 2
> QPixmap: It is not safe to use pixmaps outside the GUI thread
> QPainter::end: Painter not active, aborted
>
> The problem does not occur with other Gtk style settings (e.g. Nuvola).
> I'm not sure if the problem is with the Qt wrapper, Gtk+ or my code.
>
> FWIW I'm running Debian stable, with Gtk+ 2.20.
>
> Any ideas?
> James
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