DRM/KMS support

[oomek]

I'm curious what is your stance on adding an implementation of DRM/KMS subsystem on Linux.

[Laurent]

When you ask for a feature, please at least explain what it is, and how it would benefit to SFML. I have no idea about what DRM/KMS is, and even after a quick search, I have no idea why we would support it in SFML.

[oomek]

DRM serves the same function a X11 to open a window and reserve a surface, but with better latency and performance as it's closer to the metal.

[oomek]

Mickelson added DRM/KMS support for Linux and Raspbian(RPI4) to his fork sfml-pi yesterday. Would you be interested merging it now with the master? sfml-pi is still 2.4.2

https://github.com/mickelson/sfml-pi/commit/4b7d415e1464fa98689130b4f7531d9b986c1430

[eXpl0it3r]

Nice! I think if you or Mickelson want to rebase/cherry-pick the change onto SFML master, this would certainly be considered.

[oomek]

A little heads up.

The DRM backend is almost finished. But we stumbled across an issue that we can't find an elegant way aroud. There was a problem with rendering locking up after pressing the Enter key. We discovered that it was due to the keyboard input being passed to the terminal underneath. We solved that by grabbing an exclusive rights to all keyboard events in /dev/input by calling `ioctl(*itr, EVIOCGRAB, 1);` unfortunately this left us unavle to generate a TextEvent. Can you think of any way of converting a keycode to utf32 without relying on tables for each codepage like in SDL?

[eXpl0it3r]

Did you manage to make further progress on this or are you still stuck on the same issue?
If so, maybe I could try and summon binary1248

[oomek]

Sorry, I forgot to follow up on this topic. The SFML-PI is working ok now, all issues have been squashed. I've updated it with baseline commits up to 2.5.1, but It would be really nice to be able to merge it with the baseline. I'm just wondering if all things we've added conform with your structure.

EDIT: My 2.5.1 PR for SFML-PI is still waiting to be merged. Mickelson has sometimes long gaps in activity. I think it's what is happening now. Another reason to go SFML baseline.

[oomek]

This is a follow up to a discussion from Discord.

Many users would be really happy to see DRM window management from SFML-PI to be integrated into the baseline. As I mentioned before, I tried to keep SFML-PI up to date with selective patches from 2.5.1, but WindowBase isn't there. Preparing a PR for the current master is a bit over my head to be honest, so I'm asking for help.

SFML-PI has been running well on Linux and Raspbian. All the code under SFML_RPI flag is obsolete because it was only Raspberry PI 3 specific. SFML_DRM flag covers all x86 linux machines and Raspbian on PI3 and PI4 with KMS driver.

https://github.com/mickelson/sfml-pi/