I have XFCE4 on a Fedora 30 machine that is up to date (kernel 5.2.15, XFCE 4.14). After the 4.14 update, when I enable the compositor, I get graphic glitches that I didn't get before. Disabling the compositor solves the problem but I prefer to have it on :^)
The GPU is:
02:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Raven Ridge [Radeon Vega Series / Radeon Vega Mobile Series] (rev c4)
and X is using the amdgpu driver (from /var/log/Xorg.0.log):
[ 428.948] (II) AMDGPU: Driver for AMD Radeon:
All GPUs supported by the amdgpu kernel driver
[ 428.967] (II) AMDGPU(0): [KMS] Kernel modesetting enabled.
[ 428.967] (II) AMDGPU(0): Creating default Display subsection in Screen section
"Default Screen Section" for depth/fbbpp 24/32
[ 428.967] (==) AMDGPU(0): Depth 24, (--) framebuffer bpp 32
[ 428.967] (II) AMDGPU(0): Pixel depth = 24 bits stored in 4 bytes (32 bpp pixmaps)
[ 428.967] (==) AMDGPU(0): Default visual is TrueColor
[ 428.967] (==) AMDGPU(0): RGB weight 888
[ 428.967] (II) AMDGPU(0): Using 8 bits per RGB (8 bit DAC)
[ 428.967] (--) AMDGPU(0): Chipset: "Unknown AMD Radeon GPU" (ChipID = 0x15dd)
Is it a known problem, or is it on my part? Thanks!
I do not know about AMD GPUs (I don;t have any such hardware at hand), but chances are the issues are with GL rather than compositing itself.
Try switching to Xpresent as vblank mode (that should work well with AMD) and would rule out a problem with GL.
To do so, just type the following command in a terminal:
$ xfconf-query -c xfwm4 -p /general/vblank_mode -s xpresent
And log out/log on to restart the session.
Thanks for your answer, it removed the glitches!