Follow-up change from enabling DPI awareness, which caused some style elements (for instance check boxes) to be rendered incorrectly on non-primary displays, when there is a difference in DPI between displays. Use two approaches to get system metrics and themes: * Use forDpi() API variants and query at 96 DPI for style metrics, that are in device independent pixels. These are metrics which are used for layout calculations. * Get theme metrics at the target display DPI, and scale to device independent pixels when needed. This is used for OpenThemeData(), since this theme is used for drawing as well and needs to be in device pixels. One approach is not used any more: * Get metrics for the main display, and scale by the ratio between the main and target display. Change the theme cache to cache themes per window handle (HWND). This is required since OpenThemeData() returns theme data for a specific DPI, which means we can no longer use a shared cache. Clear the cache on theme change, DPI change, and when the window is destroyed. This handles cache invalidation when the window is moved to a different screen, and also when the DPI for a screen is changed. Move the cache implementation to QWindowsStyleSupport in QtGui, where it can be accessed by both the style and windows platform plugins. Task-number: QTBUG-110681 Change-Id: I5a4ff3a3753762bad8a51d08e51e8013bc7816a1 Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org> Reviewed-by: Jøger Hansegård <joger.hansegard@qt.io> Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>