bug#81580: 30.2; frame resizing does not work under KDE Plasma / Wayland

This problem was discussed on the Emacs-devel mailing list in December last
year. Jens Schmidt suggested adding a window rule in KDE Plasma's System
Settings, see
https://lists.gnu.org/archive/html/emacs-devel/2025-12/msg00611.html

This is of course not a satisfactory solution, but it works for me. I'm
running the PGTK build (master) on Wayland, and if I disable the KDE window
rule, I only run into the problem if I run with GDK_BACKEND=x11, which is
an unsupported combination.

I have enabled pixelwise resize in my init file, but that setting does not
seem to make a difference. If I start emacs with -Q, the default is to
resize by character and that works fine under Wayland, too.


On Sat, 8 Aug 2026 at 19:50, martin rudalics <[email protected]> wrote:

>  >> Under the KDE Plasma window manager, it is normal to be able to
>  >> resize a window by dragging one of its borders or one of its corners
>  >> with the mouse. This has worked for me, for Emacs and most other
>  >> programs, for the last 20 years, under X11. Under Wayland, however,
>  >> this does not work for Emacs (it still works for most other programs):
>  >> The first attempt to resize it changes the size only by a few pixels,
>  >> and further attempts don't change it at all any more — or by several
>  >> dozens of pixels, which feels like "random" behaviour.
>  >>
>  >> Find attached a video of the interaction, on an Emacs instance
>  >> opened through 'emacs -q'.
>  >>
>  >> Platform details:
>  >> Distro: Kubuntu 26.04
>  >> Windowing system: Wayland
>  >> KDE Plasma version: 6.6.5
>  >>
>  >> This workaround from
>  >>
> https://www.reddit.com/r/emacs/comments/1p0h08g/cant_resize_emacs_frame_by_dragging_frame_corners/
>  >> works: adding this line to $HOME/.emacs:
>  >> (setq frame-resize-pixelwise t)
>  >>
>  >> But I claim that as a user, I should not need to do this workaround. In
>  >> other words, Emacs should allow resizing its frame by default.
>  >> Why?
>  >> 1) Because that is what a normal user expects when most other programs
>  >> allow resizing their windows in this way.
>  >> 2) Because the documentation of this variable
>  >>
> https://www.gnu.org/software/emacs/manual/html_node/elisp/Frame-Size.html#index-frame_002dresize_002dpixelwise
>  >> suggests that it is only needed for making maximized/full-screen frames
>  >> work.
>
> The Elisp manual entry for 'frame-resize-pixelwise' says that
>
>       Dragging the external border with the mouse is
>       done character-wise provided the window manager is willing to
>       process the corresponding size hints.
>
> Apparently your KDE Plasma is no more willing to do that.
>
>  >> But here, the Maximize button works perfectly fine; it's the
>  >> resizing with a mouse that does not work.
>  >
>  > I think this is a known problem, caused by Wayland and GTK.  Our
>  > recommendation is to use the PGTK build on Wayland.
>  >
>  > Martin, any comments or suggestions?
>
> It's apparently a new problem.  Emacs by default prescribes to resize
> frames character-wise.  This has worked for decades on window managers
> under X11 while it never worked on Windows.  Latest versions of KDE and
> GNOME are exclusively based on Wayland and whether the X11 compatibility
> layer can handle character-wise resizing is beyond my knowledge.  Maybe
> Johan who is on KDE Plasma can say more.  Pure Wayland cannot resize
> character-wise and the PGTK build does not support it either.
>
> Ceterum censeo 'frame-resize-pixelwise' will have to default to t sooner
> or later anyway and will be usable only with older window managers and
> non-GTK X builds (maybe).
>
> martin
>