[Interest] Qt 6.5 NOT supporting Dark mode on Windows

[Volker Hilsheimer]

On 2 Jun 2023, at 17:26, David C. Partridge <david.partridge at perdrix.co.uk> wrote:

I am most unhappy to have to report that I  just had a bug report https://bugreports.qt.io/browse/QTBUG-112653 closed WON’T DO for a problem I reported with handling of Dark/Light mode switching.

The reason given was that Qt 6.5 won’t support Dark mode on Windows.

This seems more than a bit out of order given the fanfare about support of Dark Mode in Qt 6.5 in the announcement and the blog e.g.: here<https://www.qt.io/blog/dark-mode-on-windows-11-with-qt-6.5>

David


Hi David,

We do support dark mode on Windows, but not if the native (UxTheme based) style is used as that style doesn’t use the palette to render controls, and instead relies on the UxTheme system library, which never provides dark-mode assets. That’s what Axel tried to communicate in the comment. As you are using Fusion as the application style, this limitation doesn’t apply to you, and you will get the dark palette in dark mode, and the light palette in light mode.

However, the signal you are handling gets emitted to inform clients that the system theme (as seen by the QStyleHints) has changed. The palette changes in response to that (often asynchronously, and after giving the current style a chance to polish and override the system palette). By the time the signal gets emitted, the palette is still the old one. This is by design - the theme changes, and the palette changes in response to it.

To do what you intend to do, handle the ApplicationPaletteChange event in your UI. You can then evaluate the value of QStyleHints::colorScheme API to decide how you want to modify your style sheet.

Volker

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