[Interest] Qt-6.10.2 Widgets - Qt::CustomizeWindowHint Is Broken on Windows

[Wladimir Leuschner]

Hi,

The patch that caused the regression is now reverted and in 6.10.3 the old behaviour should be there again. Regarding the Window Icon when using Qt::CustomizeWindowHint, there is an answer by Volker Hilsheimer in the comments of https://qt-project.atlassian.net/browse/QTBUG-143832.

Best regards,

Wladimir Leuschner

Public
________________________________
Von: coroberti <coroberti at gmail.com>
Gesendet: Freitag, 6. Februar 2026 08:00
An: Wladimir Leuschner <wladimir.leuschner at qt.io>; Qt Interest <interest at qt-project.org>
Betreff: Re: [Interest] Qt-6.10.2 Widgets - Qt::CustomizeWindowHint Is Broken on Windows

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On Tue, Feb 3, 2026 at 8:45 PM coroberti <coroberti at gmail.com<mailto:coroberti at gmail.com>> wrote:
On Tue, Feb 3, 2026 at 7:02 PM Wladimir Leuschner <wladimir.leuschner at qt.io<mailto:wladimir.leuschner at qt.io>> wrote:

thank you for reporting the bug. This behaviour is indeed a regression and was introduced with https://codereview.qt-project.org/c/qt/qtbase/+/619145 to 6.10.2 and 6.11beta2 by me. Sorry for that. A bug report related to the issue seems already created with https://qt-project.atlassian.net/browse/QTBUG-143832. In case you have additions to the report you are welcome to comment on the bugtracker.
Best regards,
Wladimir Leuschner

________________________________
Von: Interest <interest-bounces at qt-project.org<mailto:interest-bounces at qt-project.org>> im Auftrag von coroberti <coroberti at gmail.com<mailto:coroberti at gmail.com>>
Gesendet: Dienstag, 3. Februar 2026 11:35
An: Qt Interest <interest at qt-project.org<mailto:interest at qt-project.org>>
Betreff: [Interest] Qt-6.10.2 Widgets - Qt::CustomizeWindowHint Is Broken on Windows

Hi,
Qt::CustomizeWindowHint was removing the three right-angle controls from a window for many years,
but it seems to be now broken for Qt-6.10 at least on Windows.

 Qt::Window| Qt::WindowTitleHint |  Qt::CustomizeWindowHint
Thus, we were getting a window with a title-bar but without the 3 controls from the right side.

Status for now is:
[image.png]

All controls are present and maximize is even active.

The attempts to remove the controls by getting flags and zeroing the bit for flags
like & ~ individual hint - all failed.

The only workaround that works 4me is adding the flag Qt::MSWindowsFixedSizeDialogHint - the consequence is that the image icon gets out.
You can compile versus the Qt-6.10.2 and easily reproduce the break by using the Windows Flags Example.
https://doc.qt.io/archives/qt-5.15/qtwidgets-widgets-windowflags-example.html
and the code:
https://code.qt.io/cgit/qt/qtbase.git/tree/examples/widgets/widgets/windowflags?h=5.15

Am I the only one to see it or most people do not advance to the latest Qt?


Hi,
Even if it were reversed, there is still an issue with presentation of the left angle Windows icon on the window.
Perhaps the issue is the general for Qt-6.10 series.

When the flag  Qt::CustomizeWindowHint is set, the small windows icon is not shown
unless one adds ad least a single control like flags |= Qt::WindowCloseButtonHint

It is just ignored:
this->setWindowIcon(QIcon(appIconPath));

Thanks,
Robert
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