Window flickering on Ubuntu 24.04 in Lazarus 3.8
lazarus / 1-Linux

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dvhx · 2025-04-07 14:58

I upgraded from Ubuntu 22.04 to Ubuntu 24.04 (it was clean install on
new SSD drive). I'm using JWM window manager. When I run any app made
in lazarus (including lazarus itself) there is weird flickering of the
window. Sometimes the app doesn't start until I alt+tab twice. I
thought it was disto's lazarus issue so I uninstalled it and installed
Lazarus 3.8 (rev Unknown) FPC 3.2.2 x86_64-linux-gtk2 from
sourceforge. The issue ramains, I tried older JWM (from 22.04 where it
worked) but that didn't help. I tried openbox wm it's doing it there
as well. I tried few other WM and in some it is worse, for example in
miwm the window just slowly flows up in a flickering manner. It's
relatively ok for empty window but as I add components (main menu,
memo alClient) it gets progressively worse. If I change window
left/top/width/height in FormCreate the flickering is worse, sometimes
it never stops (until double Alt+Tab). The lazarus itself is doing it
too. I tried sleep(100) and application.processMessages in random
places but it didn't help.

This is what it looks like in JWM:
https://www.youtube.com/watch?v=qo7U9hzwyeo
This is what it looks like in MIWM:
https://www.youtube.com/watch?v=gBWfno9rE9M

It seems like some kind of discrepancy between WM's desired window
size and Lazarus desired window size and they fighting each other.

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TRon · 2025-04-07 16:08

The question that should be answered is what display server is being
used.

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dvhx · 2025-04-07 19:15

Xorg

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TRon · 2025-04-08 00:02

In case being sure that ubuntu is not using wayland (which is the
default) then you could try the latest release candidate of Lazarus
(4.0RC3) and see if that improves the situation.

Other than that, sorry to say, no idea.

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dvhx · 2025-04-08 09:07

These are only my apps so for now I used BorderStyle = bsSingle and
I'll wait for 4.0