The Progress With KDE Plasma 6's KWin HDR Support

Following last month's Red Hat hosted HDR hackfest that brought together many Linux desktop stakeholders from GPU driver developers to desktop environment developers, KDE developer Xaver Hugl has shared an update on the progress being made for high dynamic range (HDR) display support from the KWin side.

Xaver participated in the recent HDR hackfest and is helping lead the charge on KDE support for HDR displays. Xaver shared in a blog post today:

"With the Wayland protocol that’s being worked on, applications tag their content with a colorspace and some other metadata, and the compositor will do whatever conversions are necessary to show it correctly on the used display, using shaders or more efficient fixed function hardware blocks on the GPU.
...
We didn’t do a lot of hacking at the hackfest, but I did manage to drive an HDR screen with a wide color gamut and with HDR mode enabled, while having KWin do the required color conversions to make SDR content look correct.

Last week I was also at the Plasma 6 sprint in Augsburg, which was also amazing, and while it was mostly unrelated to HDR, Kai Uwe happened to have a portable OLED monitor… so of course I immediately started testing KWin with HDR on it. Piling some more hacks on top of what I put together at the hackfest, I could show a video in “HDR” surrounded by SDR content.

I write “HDR” in quotes because I didn’t actually have the time to implement a proper HDR test client (yet) and only hardcoded KWin to boost the brightness range of the video player. Even this super simple hack already looks amazing though, especially on the OLED screen.

Since then I polished up the code, fixed lots of KWin effects to do the required color conversions, and now the first bits of basic HDR and color management support are merged in KWin! If you have a screen capable of HDR and/or a wide color gamut, and a Plasma 6 session built from git master, you can test it yourself by simply enabling the features with kscreen-doctor (a GUI for it will come later). In an ideal world, after adjusting the SDR brightness level, it should look exactly like having the features disabled..."

As for where the KDE HDR support is at the moment in development, Xaver went on to add:

"Enabling HDR just to get an image that looks the same is pretty lame for an end user, the actually interesting parts are when it comes to actually gaming in HDR, playing HDR videos or painting in Krita... for those use cases however, a lot more has to fall into place than KWin being able to do color conversions. There is no way to give a good estimate for when the Wayland protocol will be ready, let alone when applications will be using it, so I’m not even gonna try.

I am however quite optimistic about the future of HDR and color management on Linux. It’s all progressing pretty quickly and even just being able to fix the colors for sRGB content on wide color gamut displays with a one click solution is already a pretty good step up over what we had before."

Read more about the herculean KDE HDR effort over on Xaver's blog. It's great seeing this progress being made and hopefully for Plasma 6.0 those with HDR displays will begin enjoying the fruits of this effort that has long been a sore spot for Linux desktop capabilities.