Emacs GUI window intermittently freezes when resizing
Affected version
- Fedora 38
- Mutter 44 /
main
branch - Wayland (haven't tried Xorg)
Bug summary
When resizing a GUI window of Emacs (which uses the x11 backend of GTK3) diagonally, the window intermittently freezes.
Steps to reproduce
- Open Emacs window. Default size, much smaller than the screen.
- Move Emacs window to top of screen, near the left edge.
- Resize Emacs window
diagonallywith the mouse, keep holding the mouse button. - While still holding the mouse button, move the cursor to the bottom / right edge of the screen.
- Keep moving the cursor away from and back to the bottom / right edge of the screen, until the Emacs window freezes.
Resizing with the keyboard seems unaffected.
Resizing only horizontally or vertically doesn't seem to reproduce it.
It seems easier to reproduce with another X window behind Emacs (might just be placebo, since I'm not always able to reproduce quickly).
I've found two methods to unfreeze the frozen window:
- Continue resizing while it's frozen, at some point it will unfreeze (and possibly freeze again later)
- Alt-Tab to another X window and back
If the mouse button is released while the window is frozen, only method 2 works.
What happened
Sooner or later the window freezes: the size stops tracking the mouse cursor, and the window contents stop updating (even after releasing the mouse button).
(I'm using "freeze"/"frozen" as general terms, I'm not sure it's related to the corresponding mutter window management state)
This is a regression in mutter 44. I haven't been able to get a conclusive bisect result (again because I can't always reproduce quickly), but things are pointing to it starting in !2175 (merged).
What did you expect to happen
The window should never freeze.