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

[Wladimir Leuschner]

Hi,

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> im Auftrag von coroberti <coroberti at gmail.com>
Gesendet: Dienstag, 3. Februar 2026 11:35
An: Qt Interest <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?

Thanks.

Kind regards,
Robert Iakobashvili
............................

Confidential
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