Drawing issues with Intel HD530/630, 11th Gen Intel UHD

Using minimal example attached, when clicking on check box, background becomes white instead of red. Also see screenshots.

Also, with QQuickStyle::setStyle("Universal") (which sets hover enabled), a more maximum example of similar code resulted in blue/black triangles. This was difficult to reproduce so the example is not attached as of yet.

Tested on Windows 10 with the following Intel driver versions, all with the same result.

• 22.20.16.4836
• 23.20.16.4849
• 23.20.16.4973
• 24.20.100.6025
• 24.20.100.6136

Further investigation revealed that the  offending commit for the minimal example is in qtdeclarative as seen here:

https://codereview.qt-project.org/gitweb?p=qt/qtdeclarative.git;a=commitdiff;h=ba05397ad723fa19125eb5ca2f91c7f437b2148

Building Qt with -DQSG_SEPARATE_INDEX_BUFFER fixes the bug. However, this commit is somewhere between Qt 5.10 and 5.11 and when rebuilding 5.11 with -DQSG_SEPARATE_INDEX_BUFFER the bug still exists. In general it appears that it does relate to the index buffer being separate to the vertex buffer.