GTK4 application "resist" AltSnap control

[shodanx2]

Here is short demonstration of the behaviour,

This could be a general GTK4 problem, or a specific misconfiguration of Gajim's use of GTK4.

This problem started happening in Gajim version 2.0.0 which updated to GTK4.

2026-02-27.13H08s48.X.mp4

[shodanx2]

Here is another view,
Due to the low frame rate, it's hard to tell, but when the window is being "hotstretched" It flickers back and forth at very high speed between the original dimensions and the dimensions that AltSnap is trying to give it.

I think what is happening, is that the application knows it X Y width height, and is actively resisting being resized externally.

2026-02-27_13h12s47_x.mp4

[shodanx2]

This issue is being discussed in Gajim issue reporting tool.

https://dev.gajim.org/gajim/gajim/-/issues/12348
https://dev.gajim.org/gajim/gajim/-/issues/12398

Determined to be a GTK4 issue, GTK people have been notified.
https://gitlab.gnome.org/GNOME/gtk/-/issues/5327

[RamonUnch]

Interesting, the term "resist" is very telling in this case.
AltSnap uses the basing Windows API:

SetWindowsPos(hwnd, ...)

This is the only documented way to move a window on Windows. MoveWindow(hwnd,...) does the same and is just a wrapper with less parameters.

So I do not see what AltSnap could do more, unfortunately.
If you are able to get a sequence of windows API call to moth this window I will look into it.
The funny thing is that native resizing works but It seems windows used other internal mechanism to move/resize windows that is not available public API.