KWIN Direct Scan Out (default in newer plasma 6 releases) causes cropped fullscreen content

[theofficialgman]

Is there an existing issue for this?

• I have searched the existing issues

Is your issue described in the documentation?

• I have read the documentation

Is your issue present in the latest beta/pre-release?

This issue is present in the latest pre-release

Describe the Bug

Fullscreen applications in KDE Plasma with fractional scaling are cropped in sunshine/moonlight when kwin direct scan out under wayland (kms, not XDG portal since that force disables direct scanout due to compositing always being enabled) is enabled (which is the default).

Disabling it explicitly is a workaround for the sunshine bug.

eg: in /etc/environment, put:
KWIN_DRM_NO_DIRECT_SCANOUT=1

I have also documented this issue here https://bugs.kde.org/show_bug.cgi?id=518901 (even if the underlying bug is with sunshine) to make this wider known with the kde developers who added this feature that it regressed sunshine.

Expected Behavior

Fullscreen applications appear as normal (as they do on the actual display).

Additional Context

No response

Host Operating System

Linux

Operating System Version

KDE Neon 24.04

Architecture

amd64/x86_64

Package

Linux - deb

GPU Type

AMD

GPU Model

RX 9600

GPU Driver/Mesa Version

26.0.4

Capture Method

KMS (Linux)

Apps

Log output

[2026-04-12 20:52:48.370]: Info: Sunshine version: 2026.412.25828 commit: ba1f3bba3a5cc98a2db12c25569020e32b962cd2
[2026-04-12 20:52:48.370]: Info: Package Publisher: LizardByte
[2026-04-12 20:52:48.370]: Info: Publisher Website: https://app.lizardbyte.dev
[2026-04-12 20:52:48.370]: Info: Get support: https://app.lizardbyte.dev/support
Cannot load libcuda.so.1
[2026-04-12 20:52:48.371]: Error: Couldn't load cuda: -1
[2026-04-12 20:52:48.371]: Info: [wayland] Found display [wayland-0]
[2026-04-12 20:52:48.371]: Info: [wayland] Found interface: zxdg_output_manager_v1(31) version 3
[2026-04-12 20:52:48.371]: Info: [wayland] Found interface: zwp_linux_dmabuf_v1(57) version 5
[2026-04-12 20:52:48.371]: Info: [wayland] Found interface: wl_output(64) version 4
[2026-04-12 20:52:48.371]: Warning: [wlgrab] Missing Wayland wire for wlr-export-dmabuf
[2026-04-12 20:52:48.371]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:52:48.372]: Info: [wayland] Found display [wayland-0]
[2026-04-12 20:52:48.372]: Info: [wayland] Found display [wayland-0]
[2026-04-12 20:52:48.372]: Info: [wayland] Found interface: zxdg_output_manager_v1(31) version 3
[2026-04-12 20:52:48.372]: Info: [wayland] Found interface: zwp_linux_dmabuf_v1(57) version 5
[2026-04-12 20:52:48.372]: Info: [wayland] Found interface: wl_output(64) version 4
[2026-04-12 20:52:48.372]: Info: [wayland] Resolution: 3840x2160
[2026-04-12 20:52:48.372]: Info: [wayland] Offset: 0x0
[2026-04-12 20:52:48.372]: Info: [wayland] Logical size: 2560x1440
[2026-04-12 20:52:48.372]: Info: [wayland] Name: DP-1
[2026-04-12 20:52:48.372]: Info: [wayland] Found monitor: LG Electronics LG HDR 4K
[2026-04-12 20:52:48.372]: Info: -------- Start of KMS monitor list --------
[2026-04-12 20:52:48.372]: Info: Monitor 0 is DP-1: LG Electronics LG HDR 4K
[2026-04-12 20:52:48.372]: Info: --------- End of KMS monitor list ---------
[2026-04-12 20:52:48.471]: Info: // Testing for available encoders, this may generate errors. You can safely ignore those errors. //
[2026-04-12 20:52:48.472]: Info: Trying encoder [nvenc]
[2026-04-12 20:52:48.472]: Info: Screencasting with KMS
[2026-04-12 20:52:48.472]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:52:48.474]: Error: Couldn't find monitor [0]
[2026-04-12 20:52:48.474]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:52:48.474]: Error: Couldn't find monitor [0]
[2026-04-12 20:52:48.674]: Info: Screencasting with KMS
[2026-04-12 20:52:48.674]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:52:48.675]: Error: Couldn't find monitor [0]
[2026-04-12 20:52:48.675]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:52:48.675]: Error: Couldn't find monitor [0]
[2026-04-12 20:52:48.875]: Info: Encoder [nvenc] failed
[2026-04-12 20:52:48.875]: Info: Trying encoder [vulkan]
[2026-04-12 20:52:48.875]: Info: Screencasting with KMS
[2026-04-12 20:52:48.875]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:52:48.875]: Info: Found monitor for DRM screencasting
[2026-04-12 20:52:48.875]: Info: Found connector ID [100]
[2026-04-12 20:52:48.876]: Info: Found cursor plane [83]
[2026-04-12 20:52:48.876]: Info: Creating encoder [h264_vulkan]
[2026-04-12 20:52:48.876]: Info: Color coding: SDR (Rec. 601)
[2026-04-12 20:52:48.876]: Info: Color depth: 8-bit
[2026-04-12 20:52:48.876]: Info: Color range: JPEG
WARNING: radv is not a conformant Vulkan implementation, testing use only.
WARNING: radv is not a conformant Vulkan implementation, testing use only.
[2026-04-12 20:52:48.918]: Info: Streaming bitrate is 1000000
[2026-04-12 20:52:48.919]: Info: Vulkan encode using GPU: AMD Radeon Graphics (RADV GFX1200)
[2026-04-12 20:52:48.928]: Info: Creating encoder [hevc_vulkan]
[2026-04-12 20:52:48.928]: Info: Color coding: SDR (Rec. 601)
[2026-04-12 20:52:48.928]: Info: Color depth: 8-bit
[2026-04-12 20:52:48.928]: Info: Color range: JPEG
WARNING: radv is not a conformant Vulkan implementation, testing use only.
WARNING: radv is not a conformant Vulkan implementation, testing use only.
[2026-04-12 20:52:48.974]: Info: Streaming bitrate is 1000000
[2026-04-12 20:52:48.978]: Info: Vulkan encode using GPU: AMD Radeon Graphics (RADV GFX1200)
[2026-04-12 20:52:48.991]: Info: Creating encoder [av1_vulkan]
[2026-04-12 20:52:48.991]: Info: Color coding: SDR (Rec. 601)
[2026-04-12 20:52:48.991]: Info: Color depth: 8-bit
[2026-04-12 20:52:48.991]: Info: Color range: JPEG
WARNING: radv is not a conformant Vulkan implementation, testing use only.
WARNING: radv is not a conformant Vulkan implementation, testing use only.
[2026-04-12 20:52:49.031]: Info: Streaming bitrate is 1000000
[2026-04-12 20:52:49.032]: Info: Vulkan encode using GPU: AMD Radeon Graphics (RADV GFX1200)
[2026-04-12 20:52:49.040]: Info: Screencasting with KMS
[2026-04-12 20:52:49.040]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:52:49.040]: Info: Found monitor for DRM screencasting
[2026-04-12 20:52:49.041]: Info: Found connector ID [100]
[2026-04-12 20:52:49.041]: Info: Found cursor plane [83]
[2026-04-12 20:52:49.041]: Info: Creating encoder [hevc_vulkan]
[2026-04-12 20:52:49.041]: Info: Color coding: SDR (Rec. 709)
[2026-04-12 20:52:49.041]: Info: Color depth: 10-bit
[2026-04-12 20:52:49.041]: Info: Color range: JPEG
WARNING: radv is not a conformant Vulkan implementation, testing use only.
WARNING: radv is not a conformant Vulkan implementation, testing use only.
[2026-04-12 20:52:49.082]: Info: Streaming bitrate is 1000000
[2026-04-12 20:52:49.086]: Info: Vulkan encode using GPU: AMD Radeon Graphics (RADV GFX1200)
[2026-04-12 20:52:49.096]: Info: Creating encoder [av1_vulkan]
[2026-04-12 20:52:49.096]: Info: Color coding: SDR (Rec. 709)
[2026-04-12 20:52:49.096]: Info: Color depth: 10-bit
[2026-04-12 20:52:49.096]: Info: Color range: JPEG
WARNING: radv is not a conformant Vulkan implementation, testing use only.
WARNING: radv is not a conformant Vulkan implementation, testing use only.
[2026-04-12 20:52:49.138]: Info: Streaming bitrate is 1000000
[2026-04-12 20:52:49.139]: Info: Vulkan encode using GPU: AMD Radeon Graphics (RADV GFX1200)
[2026-04-12 20:52:49.156]: Info: 
[2026-04-12 20:52:49.157]: Info: // Ignore any errors mentioned above, they are not relevant. //
[2026-04-12 20:52:49.157]: Info: 
[2026-04-12 20:52:49.157]: Info: Found H.264 encoder: h264_vulkan [vulkan]
[2026-04-12 20:52:49.157]: Info: Found HEVC encoder: hevc_vulkan [vulkan]
[2026-04-12 20:52:49.157]: Info: Found AV1 encoder: av1_vulkan [vulkan]
[2026-04-12 20:52:49.157]: Info: Starting system tray
[2026-04-12 20:52:49.160]: Info: Configuration UI available at [https://localhost:47990]
[2026-04-12 20:52:49.160]: Info: Adding avahi service garrett-desktop
[2026-04-12 20:52:49.197]: Info: System tray created
[2026-04-12 20:52:49.197]: Info: Starting main loop
[2026-04-12 20:52:50.137]: Info: Avahi service garrett-desktop successfully established.
[2026-04-12 20:53:00.357]: Info: // Testing for available encoders, this may generate errors. You can safely ignore those errors. //
[2026-04-12 20:53:00.357]: Info: Trying encoder [nvenc]
[2026-04-12 20:53:00.357]: Info: Screencasting with KMS
[2026-04-12 20:53:00.357]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:53:00.357]: Error: Couldn't find monitor [0]
[2026-04-12 20:53:00.358]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:53:00.358]: Error: Couldn't find monitor [0]
[2026-04-12 20:53:00.558]: Info: Screencasting with KMS
[2026-04-12 20:53:00.558]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:53:00.558]: Error: Couldn't find monitor [0]
[2026-04-12 20:53:00.558]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:53:00.558]: Error: Couldn't find monitor [0]
[2026-04-12 20:53:00.758]: Info: Encoder [nvenc] failed
[2026-04-12 20:53:00.758]: Info: Trying encoder [vulkan]
[2026-04-12 20:53:00.758]: Info: Screencasting with KMS
[2026-04-12 20:53:00.758]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:53:00.759]: Info: Found monitor for DRM screencasting
[2026-04-12 20:53:00.759]: Info: Found connector ID [100]
[2026-04-12 20:53:00.759]: Info: Found cursor plane [83]
[2026-04-12 20:53:00.759]: Info: Creating encoder [h264_vulkan]
[2026-04-12 20:53:00.759]: Info: Color coding: SDR (Rec. 601)
[2026-04-12 20:53:00.759]: Info: Color depth: 8-bit
[2026-04-12 20:53:00.759]: Info: Color range: JPEG
WARNING: radv is not a conformant Vulkan implementation, testing use only.
WARNING: radv is not a conformant Vulkan implementation, testing use only.
[2026-04-12 20:53:00.807]: Info: Streaming bitrate is 1000000
[2026-04-12 20:53:00.807]: Info: Vulkan encode using GPU: AMD Radeon Graphics (RADV GFX1200)
[2026-04-12 20:53:00.823]: Info: Creating encoder [hevc_vulkan]
[2026-04-12 20:53:00.823]: Info: Color coding: SDR (Rec. 601)
[2026-04-12 20:53:00.823]: Info: Color depth: 8-bit
[2026-04-12 20:53:00.823]: Info: Color range: JPEG
WARNING: radv is not a conformant Vulkan implementation, testing use only.
WARNING: radv is not a conformant Vulkan implementation, testing use only.
[2026-04-12 20:53:00.867]: Info: Streaming bitrate is 1000000
[2026-04-12 20:53:00.870]: Info: Vulkan encode using GPU: AMD Radeon Graphics (RADV GFX1200)
[2026-04-12 20:53:00.891]: Info: Creating encoder [av1_vulkan]
[2026-04-12 20:53:00.891]: Info: Color coding: SDR (Rec. 601)
[2026-04-12 20:53:00.891]: Info: Color depth: 8-bit
[2026-04-12 20:53:00.891]: Info: Color range: JPEG
WARNING: radv is not a conformant Vulkan implementation, testing use only.
WARNING: radv is not a conformant Vulkan implementation, testing use only.
[2026-04-12 20:53:00.936]: Info: Streaming bitrate is 1000000
[2026-04-12 20:53:00.937]: Info: Vulkan encode using GPU: AMD Radeon Graphics (RADV GFX1200)
[2026-04-12 20:53:00.956]: Info: Screencasting with KMS
[2026-04-12 20:53:00.956]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:53:00.956]: Info: Found monitor for DRM screencasting
[2026-04-12 20:53:00.956]: Info: Found connector ID [100]
[2026-04-12 20:53:00.957]: Info: Found cursor plane [83]
[2026-04-12 20:53:00.957]: Info: Creating encoder [hevc_vulkan]
[2026-04-12 20:53:00.957]: Info: Color coding: SDR (Rec. 709)
[2026-04-12 20:53:00.957]: Info: Color depth: 10-bit
[2026-04-12 20:53:00.957]: Info: Color range: JPEG
WARNING: radv is not a conformant Vulkan implementation, testing use only.
WARNING: radv is not a conformant Vulkan implementation, testing use only.
[2026-04-12 20:53:01.001]: Info: Streaming bitrate is 1000000
[2026-04-12 20:53:01.006]: Info: Vulkan encode using GPU: AMD Radeon Graphics (RADV GFX1200)
[2026-04-12 20:53:01.019]: Info: Creating encoder [av1_vulkan]
[2026-04-12 20:53:01.019]: Info: Color coding: SDR (Rec. 709)
[2026-04-12 20:53:01.019]: Info: Color depth: 10-bit
[2026-04-12 20:53:01.020]: Info: Color range: JPEG
WARNING: radv is not a conformant Vulkan implementation, testing use only.
WARNING: radv is not a conformant Vulkan implementation, testing use only.
[2026-04-12 20:53:01.066]: Info: Streaming bitrate is 1000000
[2026-04-12 20:53:01.067]: Info: Vulkan encode using GPU: AMD Radeon Graphics (RADV GFX1200)
[2026-04-12 20:53:01.080]: Info: 
[2026-04-12 20:53:01.080]: Info: // Ignore any errors mentioned above, they are not relevant. //
[2026-04-12 20:53:01.080]: Info: 
[2026-04-12 20:53:01.080]: Info: Found H.264 encoder: h264_vulkan [vulkan]
[2026-04-12 20:53:01.080]: Info: Found HEVC encoder: hevc_vulkan [vulkan]
[2026-04-12 20:53:01.080]: Info: Found AV1 encoder: av1_vulkan [vulkan]
[2026-04-12 20:53:01.080]: Info: Executing [Desktop]
[2026-04-12 20:53:01.123]: Info: New streaming session started [active sessions: 1]
[2026-04-12 20:53:01.222]: Info: CLIENT CONNECTED
[2026-04-12 20:53:01.257]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:53:01.257]: Info: [wayland] Found display [wayland-0]
[2026-04-12 20:53:01.257]: Info: [wayland] Found interface: zxdg_output_manager_v1(31) version 3
[2026-04-12 20:53:01.257]: Info: [wayland] Found interface: zwp_linux_dmabuf_v1(57) version 5
[2026-04-12 20:53:01.257]: Info: [wayland] Found interface: wl_output(64) version 4
[2026-04-12 20:53:01.258]: Info: [wayland] Resolution: 3840x2160
[2026-04-12 20:53:01.258]: Info: [wayland] Offset: 0x0
[2026-04-12 20:53:01.258]: Info: [wayland] Logical size: 2560x1440
[2026-04-12 20:53:01.258]: Info: [wayland] Name: DP-1
[2026-04-12 20:53:01.258]: Info: [wayland] Found monitor: LG Electronics LG HDR 4K
[2026-04-12 20:53:01.258]: Info: -------- Start of KMS monitor list --------
[2026-04-12 20:53:01.258]: Info: Monitor 0 is DP-1: LG Electronics LG HDR 4K
[2026-04-12 20:53:01.258]: Info: --------- End of KMS monitor list ---------
[2026-04-12 20:53:01.258]: Info: Screencasting with KMS
[2026-04-12 20:53:01.258]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:53:01.258]: Info: Found monitor for DRM screencasting
[2026-04-12 20:53:01.258]: Info: Found connector ID [100]
[2026-04-12 20:53:01.258]: Info: Found cursor plane [83]
[2026-04-12 20:53:01.264]: Info: Creating encoder [hevc_vulkan]
[2026-04-12 20:53:01.264]: Info: Color coding: SDR (Rec. 709)
[2026-04-12 20:53:01.264]: Info: Color depth: 8-bit
[2026-04-12 20:53:01.264]: Info: Color range: MPEG
WARNING: radv is not a conformant Vulkan implementation, testing use only.
WARNING: radv is not a conformant Vulkan implementation, testing use only.
[2026-04-12 20:53:01.315]: Info: Streaming bitrate is 7308000
[2026-04-12 20:53:01.319]: Info: Vulkan encode using GPU: AMD Radeon Graphics (RADV GFX1200)
[2026-04-12 20:53:01.319]: Info: Minimum FPS target set to ~30fps (33.3333ms)
[2026-04-12 20:53:01.621]: Info: Found default monitor by name: alsa_output.pci-0000_03_00.1.hdmi-stereo.monitor
[2026-04-12 20:53:01.653]: Info: Opus initialized: 48 kHz, 2 channels, 96 kbps (total), LOWDELAY
[2026-04-12 20:53:03.900]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:53:03.900]: Info: [wayland] Found display [wayland-0]
[2026-04-12 20:53:03.900]: Info: [wayland] Found interface: zxdg_output_manager_v1(31) version 3
[2026-04-12 20:53:03.900]: Info: [wayland] Found interface: zwp_linux_dmabuf_v1(57) version 5
[2026-04-12 20:53:03.900]: Info: [wayland] Found interface: wl_output(64) version 4
[2026-04-12 20:53:03.900]: Info: [wayland] Resolution: 3840x2160
[2026-04-12 20:53:03.900]: Info: [wayland] Offset: 0x0
[2026-04-12 20:53:03.900]: Info: [wayland] Logical size: 2560x1440
[2026-04-12 20:53:03.900]: Info: [wayland] Name: DP-1
[2026-04-12 20:53:03.900]: Info: [wayland] Found monitor: LG Electronics LG HDR 4K
[2026-04-12 20:53:03.900]: Info: -------- Start of KMS monitor list --------
[2026-04-12 20:53:03.901]: Info: Monitor 0 is DP-1: LG Electronics LG HDR 4K
[2026-04-12 20:53:03.901]: Info: --------- End of KMS monitor list ---------
[2026-04-12 20:53:03.901]: Info: Screencasting with KMS
[2026-04-12 20:53:03.901]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:53:03.901]: Info: Found monitor for DRM screencasting
[2026-04-12 20:53:03.901]: Info: Found connector ID [100]
[2026-04-12 20:53:03.901]: Info: Found cursor plane [83]
[2026-04-12 20:53:03.907]: Info: Creating encoder [hevc_vulkan]
[2026-04-12 20:53:03.907]: Info: Color coding: SDR (Rec. 709)
[2026-04-12 20:53:03.907]: Info: Color depth: 8-bit
[2026-04-12 20:53:03.907]: Info: Color range: MPEG
WARNING: radv is not a conformant Vulkan implementation, testing use only.
WARNING: radv is not a conformant Vulkan implementation, testing use only.
[2026-04-12 20:53:03.948]: Info: Streaming bitrate is 7308000
[2026-04-12 20:53:03.952]: Info: Vulkan encode using GPU: AMD Radeon Graphics (RADV GFX1200)
[2026-04-12 20:53:03.952]: Info: Minimum FPS target set to ~30fps (33.3333ms)
[2026-04-12 20:53:18.655]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:53:18.655]: Info: [wayland] Found display [wayland-0]
[2026-04-12 20:53:18.658]: Info: [wayland] Found interface: zxdg_output_manager_v1(31) version 3
[2026-04-12 20:53:18.658]: Info: [wayland] Found interface: zwp_linux_dmabuf_v1(57) version 5
[2026-04-12 20:53:18.658]: Info: [wayland] Found interface: wl_output(64) version 4
[2026-04-12 20:53:18.658]: Info: [wayland] Resolution: 3840x2160
[2026-04-12 20:53:18.658]: Info: [wayland] Offset: 0x0
[2026-04-12 20:53:18.658]: Info: [wayland] Logical size: 2560x1440
[2026-04-12 20:53:18.658]: Info: [wayland] Name: DP-1
[2026-04-12 20:53:18.658]: Info: [wayland] Found monitor: LG Electronics LG HDR 4K
[2026-04-12 20:53:18.658]: Info: -------- Start of KMS monitor list --------
[2026-04-12 20:53:18.658]: Info: Monitor 0 is DP-1: LG Electronics LG HDR 4K
[2026-04-12 20:53:18.658]: Info: --------- End of KMS monitor list ---------
[2026-04-12 20:53:18.658]: Info: Screencasting with KMS
[2026-04-12 20:53:18.658]: Info: /dev/dri/card1 -> amdgpu
[2026-04-12 20:53:18.658]: Info: Found monitor for DRM screencasting
[2026-04-12 20:53:18.658]: Info: Found connector ID [100]
[2026-04-12 20:53:18.659]: Info: Found cursor plane [83]
[2026-04-12 20:53:18.669]: Info: Creating encoder [hevc_vulkan]
[2026-04-12 20:53:18.669]: Info: Color coding: SDR (Rec. 709)
[2026-04-12 20:53:18.669]: Info: Color depth: 8-bit
[2026-04-12 20:53:18.669]: Info: Color range: MPEG
WARNING: radv is not a conformant Vulkan implementation, testing use only.
WARNING: radv is not a conformant Vulkan implementation, testing use only.
[2026-04-12 20:53:18.710]: Info: Streaming bitrate is 7308000
[2026-04-12 20:53:18.714]: Info: Vulkan encode using GPU: AMD Radeon Graphics (RADV GFX1200)
[2026-04-12 20:53:18.714]: Info: Minimum FPS target set to ~30fps (33.3333ms)

Online logs

No response

[psyke83]

I don't think we can rely on kmsgrab always working without requiring users to take compatibility steps that may degrade overall performance. For context, see: https://bugs.kde.org/show_bug.cgi?id=504337#c42

Other compatibility issues I can think of related to KWin + kmsgrab:

• Cursor shape changes are very intensive and spike Sunshine's CPU usage, which currently causes stuttering. This is not entirely kmsgrab's fault and a PR is WIP that will help this, but the workaround specific to kmsgrab is to disable the hardware cursor plane via KWIN_FORCE_SW_CURSOR=1.
• There's already another KWin feature (not yet enabled by default, but may be in future) that causes issues with kmsgrab: KWIN_USE_OVERLAYS=1. This causes windows to flash black and/or temporarily disappear entirely when moved.

[cgutman]

Can we just make portal capture the default (and move kmsgrab to the bottom of the list)?

With newer DRM features (like color pipeline) being introduced all the time and compositors adopting more advanced DRM features like KMS offloading and hardware LUTs, kmsgrab's simplistic approach of just grabbing the primary plane will get more and more broken over time.

@theofficialgman We shouldn't bother the KDE folks (or others) about bugs affecting kmsgrab. They're right that it's a hack and we're responsible for fixing it when it (inevitably) breaks with new compositor features.

[theofficialgman]

Portal capture performance is terrible on my setup (stuttery because it only sends ~45fps when the content is 60fps). kmsgrab on the other hand works very well (full frame rate and great framepacing, as long as you use 100% scaling which I can deal with for fullscreen gaming)

[Kishi85]

Can we just make portal capture the default (and move kmsgrab to the bottom of the list)?

@cgutman You'd likely have to change the selection after all probing is done since Portalgrab will drop CAP_SYS_ADMIN and that will break KMS (this happend with #4931 and was worked around in #4969).

UPDATE: You also cannot use KMS after doing encoder probing on portalgrab as that is the point when CAP_SYS_ADMIN will be gone due to first portal_display init.

[psyke83]

We also need to keep in mind:

• portalgrab (and compositors) don't yet support HDR.
• users need physical access for first-time setup to allow the portal token to be created. Related PR, and a bypass is available, but only on KDE.
• mutter is not working nearly as well as kwin. GNOME users will not get variable rate capture, which limits maximum client-side capture rate to the host screen refresh due to a recent change. Additionally, the last time I tested on GNOME 50, when the host screen goes idle, the screencast session is terminated and can't be reestablished until the portal token is manually set up again. Right now you have to disable screen idle on GNOME for portalgrab to work reliably and not lose the cached token.

I personally use and prefer portalgrab (on KDE), and I definitely think that we should encourage its use over kmsgrab in the documentation. I also think we should document some of the known downsides of kmsgrab to clearly communicate that it can break at any time due to upstream changes in the kernel and compositors. But I think that making portalgrab the default right now might cause a huge spike in user reports due to the current quirks and drawbacks of portalgrab.