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Comment by seba_dos1 | Hacker News Reader

I generally agree with you, just wanted to note one thing: for some, GLES requirement is actually quite a big one. Getting proprietary PowerVR drivers to work on mainline kernels is a nightmare, for instance - and of course, if you don't want blobs, you can't even use that. There are plenty of devices out there that work pretty well with X11 and no GLES.

However, I believe KWin has a QPainter rendering backend available, so that's not something inherently tied to the Wayland protocol.

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There's always llvmpipe [1] as a last resort. Do you think that a Wayland compositor plus llvmpipe is inherently more CPU intensive than Xorg without a compositor using fbdev?

[1]: https://www.mesa3d.org/llvmpipe.html

Yup, it definitely is. For some hardware it may not make a big difference, but for others it will be a deal breaker.

Also, when I checked recently, wlroots seemed to not use a shadow buffer with llvmpipe, which makes it even less performant than it could be. It should be easily fixable though.

In a comment last year, Sir_Cmpwn wrote:

> We don't just paste pixels on the screen, we composite them. This involves alpha blending, projecting the scene onto an orthographic output projection, and more.

What would we lose, in usability and not just eye candy, if the "compositor" did just paste pixels onto the screen? Woudl such a compositor be as usable without GL as Xorg is?

You lose any alpha blending and ability to retain the contents of window if the app responds slowly or stops responding at all. Some other features like hidpi scaling done by compositor would also be lost. Otherwise it seems like it might be doable (although I'm not 100% sure, Wayland protocol definitely wasn't designed with this in mind), but the implementation would be so different to the standard GLES mode that it should probably be just a separate project.

A perfectly usable GUI is possible without alpha blending, isn't it? If I'm not mistaken, Windows didn't have alpha blending until Windows 2000, and it was still a runaway success.

Alpha blending and retaining the contents of windows doesn't need a full-blown compositor...

Indeed, GL is not a Wayland requirement. The core protocol only requires the compositor to support wl_shm (shared memory). Some compositors have a software-only mode (e.g. Weston, and you mentioned KWin).

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