Resize grip pointer area very small for QT apps in gnome under wayland

The resize pointer which resizes the window has very small area. So whenever i move the mouse cursor to window edge or vertex i cant seem to resize it. This happens only in QT apps (like Kate) and not on GTK apps.

I am using latest Kvantum for theming them but i am not sure that theme is the issue. I am on stable branch of manjaro and as of 15-June-2021 this issue is still there.

This issue can be clearly seen in below screencast.

Let me know if additional info is needed

Edit:
this happens only when using QT_QPA_PLATFORM=wayland flag in /etc/environment (i have installed qt5-wayland and qt6-wayland packages)

if i set QT_QPA_PLATFORM=xcb (basicall X11) then the window decorations are like gtk apps and the size is perfect.

The widget style is not influencing that mouse grab that is related to the window decoration style. My guess is that you have gtk3-classic or gtk3-nocsd-git from AUR installed. Change to the gtk3 from our repository.

Hey, happens only when using QT_QPA_PLATFORM=wayland flag in /etc/environment (i have installed qt5-wayland and qt6-wayland packages)

if i set QT_QPA_PLATFORM=xcb (basicall X11) then the window decorations are like gtk apps and the size is perfect.

Is this issue with QT ?

Are you sure there is such valid variable and working?

AFAIK there is:
QT_QPA_PLATFORM=xcb
that will use the Xwayland backend

and if you prefer Kwantum as style decoration (for widgets)
QT_STYLE_OVERRIDE="kvantum"

or you can define
QT_QPA_PLATFORMTHEME="gnome"
or
QT_QPA_PLATFORMTHEME="qt5ct"
if you want a more coherent “native” gnome look …

Yep, Its given on arch wiki here under title QT (‘run a Qt application with the Wayland plugin’)

Is not what i asked, but anyway, are you sure that all Qt application have that proper support for wayland? Qt apps on Wayland bring their own window decoration, you know … hence on gnome, i don’t see that as fiable (at least not yet); because of that QT_QPA_PLATFORM=xcb is still more reliable.

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb.
This is the output when kate is run with invalid plugin. Here is ‘wayland’ present. Is this what you were asking?

QT_STYLE_OVERRIDE="kvantum" and QT_QPA_PLATFORMTHEME="gnome" both come in /etc/environment of manjaro so its not a choice between these two. Also 'QT_STYLE_OVERRIDE=“kvantum” causes QT apps to be white on dark theme. Switching to QT_STYLE_OVERRIDE=“kvantum-dark” fixes this issue (can you reproduce this?).

This maybe the cause since this issue does not occur on vlc which is QT app. However VLC looks like the only app which is not affected. I tried a few KDE apps and deepin-music, notepadqq and all of them have wrong window decorations under wayland. So maybe this is system bug?

Oh and using xcb causes weird display issues in apps like below

which does not occur when using wayland

Here is my /etc/environment

QT_AUTO_SCREEN_SCALE_FACTOR=1
QT_QPA_PLATFORMTHEME=gnome
QT_STYLE_OVERRIDE=kvantum-dark
QT_QPA_PLATFORM=wayland 		# also install qt5-wayland & qt6-wayland

Out of 4, i added only the last one.

1 Like

I don’t use Kwantum in any of my installs
On Gnome i use

With Adwaita-qt and the color scheme from Manjaro Adwaita-Maia-Dark

There you go …

Wayland is nowhere to be used on my end, for various reasons.

i found this reddit comment

This is just the new way in Gnome. Gnome doesn’t support server-side decorations, so apps need to draw their own window decorations. The reason all Gnome apps look the same is that GTK draws the decorations, and GTK uses your GTK theme. Any application which doesn’t use GTK, including any application made with Qt, SDL, GLFW, tkinter, wkwidgets, GLEW, etc. will necessarily look out of place. There’s not really anything Qt (or any other toolkit) can do about it.

It didn’t have to be this way though. KDE, Sway, and mostly all other Wayland compositors, and every X11 DE/WM, supports server-side decorations, where the window manager draws decorations for applications which don’t explicitly ask to use client-side decorations. The only systems I know of which don’t support server-side decorations are Gnome on Wayland and Weston (the reference implementation of Wayland).

For further reading, see for example FAQ · mpv-player/mpv Wiki · GitHub. For more examples, see the countless games or applications written in SDL which support every system under the sun except for Gnome on Wayland

Is this due to Mutter not supporting Server side decorations and QT apps expects SSD?

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