QT windows with transparent backgrounds show as opaque, and don't damage properly

[coolguy1842]

Regression

Yes, started from e536b02, although this specific example had issues in 0.46.0 with blur.

Describe the bug

Left is before hack fix, right is after.

2025-04-20.15-00-29.mp4

Reproduction steps

1. Create a simple QT application with this code:

#include <QApplication>
#include <QWidget>
int main(int argc, char** argv) {
    QApplication app(argc, argv);
    QWidget widget;
    widget.setStyleSheet("background-color:rgba(0, 0, 0, 0.14);");
    widget.show();
    return app.exec();
}

2. Compile with g++ -o main main.cpp $(pkgconf Qt6Widgets -cflags --libs)
3. Run ./main and see issue

Hacky fix

I found the issue is due to the pending.opaque region in SSurfaceState, the fix is to comment line 225 in Compositor.cpp: pending.opaque = RG->region;

[vaxerski]

qt bug. Incorrectly set opaque regions.