Hi,

Describe the bug

A web page with an < input type="color" > https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/color shows a dialog with some issues (black foreground).
The bug happens when the QWebEngineView is shown in a QGraphicsView via a QGraphicsProxyWidget. Have a look at the minimal attached sample.

How to reproduce it

• Launch the sample.
• Click on the red button
• The color picker dialog appears with issues described below

Normal behavior

The color selector dialog from Qt should be displayed accordingly to the documentation:

• Qt 5 https://doc.qt.io/qt-5/qtwebengine-features.html#native-dialogs
• or Qt 6 https://doc.qt.io/qt-6/qtwebengine-features.html#native-dialogs

Observed issues

On windows 10

The dialog is white page. After some clicks, the dialog is visible. But it remains some shifting issues in the position of the dialog controls.

On linux and KDE desktop

The dialog has a black foreground.

On linux and with gtk-based desktop

When QT_QPA_PLATFORMTHEME=gtk2 or gtk3, the dialog displayed is the GTK color selector (https://docs.gtk.org/gtk4/class.ColorChooserDialog.html) instead of the Qt one. It is contradictory with the Qt documentation https://doc.qt.io/qt-6/qtwebengine-features.html#native-dialogs where the dialog should come form Qt anyway:
> In widget-based applications, the standard dialogs are based on QDialog

Illustrations

You can see screenshots of the issue on this original bug description https://github.com/OpenBoard-org/OpenBoard/issues/904.

System info and context

reproducibility : systematic
Qt : 5.15.6 and 6.4.0
OS : bug happens with : Linux and Windows
didn't check : macOS
Additional context
OS(es) detailed version (for the ones you reproduced the bug on) :
Linux : Description: KDE neon 5.27
Windows : 10

Thank you in advance for your support.