Fix crash due to style cache issue in QT<5.12.4. Fixes #39693 #39725 #39615

[luipir]

Fix crash due to style cache issue in QT<5.12.4. Fixes #39693 #39725 #39615
No tests available :/

workaround to QT bug https://bugreports.qt.io/browse/QTBUG-69204

Partially sponsored by QGIS Spanish User Group qgis.es

[nirvn]

@luipir , other than @rouault 's suggestion, fix looks good. Just in time.

I'd reduce the comment to a single line, something like
// Fix crash on old Qt versions, see #39693

[DelazJ]

Thanks @luipir for all the efforts.

[luipir]

some squash to clean commits

[luipir]

@rouault @DelazJ @nirvn let me know if I can merge or any modification more

[nyalldawson]

Just add docs, don't expand the missing doc list!

[luipir]

I followed the same as the other overloaded slots because the documentation I suppose is based on base class documentation. BTW I'll add doc.

[luipir]

added

[nyalldawson]

I'm a little confused how this fix works -- QWidget::setStyleSheet isn't virtual, so how does this intercept all attempts to set the group box style?

[luipir]

I'm a little confused how this fix works -- QWidget::setStyleSheet isn't virtual, so how does this intercept all attempts to set the group box style?

is it done calling parent setStyleSheet? or do you mean to move the fix to upper levels?

[rouault]

I'm a little confused how this fix works -- QWidget::setStyleSheet isn't virtual, so how does this intercept all attempts to set the group box style?

this won't intercept all attempts, just those done by this class. Perhaps the method should be internalSetStyleSheet() to avoid any confusion ?

[luipir]

I'm a little confused how this fix works -- QWidget::setStyleSheet isn't virtual, so how does this intercept all attempts to set the group box style?

this won't intercept all attempts, just those done by this class. Perhaps the method should be internalSetStyleSheet() to avoid any confusion ?

well.. @nyalldawson I'm confused too about why the crash happen always in the same class and does not affect the other call to setStyleSheet (175) all over the qgis code.

[luipir]

I'm a little confused how this fix works -- QWidget::setStyleSheet isn't virtual, so how does this intercept all attempts to set the group box style?

this won't intercept all attempts, just those done by this class. Perhaps the method should be internalSetStyleSheet() to avoid any confusion ?

because the crash happen only with this class, I prefered to leave the same method name to avoid to call setStyleSheet falling again in a crash.

[nyalldawson]

Should we also backport to 3.10 to be extra safe?

[nirvn]

Sure.

[nirvn]

Let's get this into 3.16 so we can ship a crash free version asap.

Code looks good. The documentation could be improved but we can do that in a follow up PR.

[msevilla00]

I updated my installation through deb [arch=amd64] https://qgis.org/ubuntugis-nightly-release bionic main and I'm still having this issue :-(

Here it is my configuration:

[nirvn]

@msevilla00 , that build is too old.

[PedroVenancio]

@msevilla00 last commit included in your build is from 5 days ago.

[msevilla00]

Ok, thanks, I did apt update & upgrade and changed... I thought included the latest fix.

I'll try with the other repos.

Cheers