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

[coroberti]

On Tue, Feb 3, 2026 at 8:45 PM coroberti <coroberti at gmail.com> wrote:

> On Tue, Feb 3, 2026 at 7:02 PM Wladimir Leuschner <
> 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> 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: 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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