Comment by jancsika | Hacker News Reader

Comment by jancsika | Hacker News Reader

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> Customer with expectations that are difficult to match. e.g., using xorg modesetting you had tearing, which is not acceptable for e.g. digital signage. Intel-drv driver had tearfree, but then new hw didn't work. Solving took more than 2 months. This is standarized in Wayland.

I'd like to know more about this one.

I mean, suppose the digital signage hardware/software supported OpenGL GPU-accelerated rendering. In that case how would Xorg tearing/tearfree matter? The software is just rendering using OpenGL so Xorg vs. Wayland shouldn't make any difference. IIRC some game dev mentioned this once, how their game is just using a toolkit doing full-screen accelerated rendering-- the underlying display server didn't really make a difference.

If I'm right, then the signage hardware must have been using non-accelerated path under Xorg.

That leaves me wondering:

* is most modern digital signage running without any GPU acceleration?

* does software rendering work well enough under Wayland to deliver smooth animation for professional use cases on underpowered hardware?

I'm just having trouble thinking of digital signage constraints that need high-enough framerate that Xorg was a problem, but also low enough that software rendering was feasible.

Even if you render with whatever you please, software, OpenGL, Vulkan, you have to communicate with Xorg to slap it on the screen, and that'll result in tearing. On my Nvidia machine, the only escape from tearing is manually enabling the full composition pipeline in Nvidia's settings application. Nothing else, even Vsync settings, can save me from it.

Could you point me in the direction of info about this? I have horrible tearing, and even enabling picom hasn't helped.

For some background on the setting, you can check out this thread [0]. My system rarely reboots and I'm the only user, so I just set this manually every single boot by popping open nvidia-settings, going to the X Screen settings, clicking Advanced, then enabling the Force Full Composition Pipeline checkbox, and applying. While I was searching, I also found a this resource [1] for automating that a bit, a few shell scripts that just call nvidia-settings and some xorg config tweaks.

[0] https://www.reddit.com/r/linux_gaming/comments/6voivr/can_an...

[1] https://unix.stackexchange.com/questions/510757/how-to-autom...

> ...I just set this manually every single boot by...

Man, folks talk about all sorts of things that X11 doesn't do. (And you have some manual steps that you do every boot (but (as you say) could easily automate.)

Me? I just have this one file:

    cat /etc/X11/xorg.conf.d/20-tearfree.conf 
    Section "Device"
     Identifier "AMD"
     Driver "amdgpu"
     Option "TearFree" "on"
     Option "VariableRefresh" "on"
    EndSection

and I get all these things that people say X11 doesn't do:

* zero tearing... whether in KDE or WindowMaker

* zero problems with my mixed-DPI displays (one 32" 2160p display, and one 24" 16:10 1200p display)

* zero problems with my mixed-refresh-rate displays (one at 60Hz and one at 59.95) (This one I've tested with my eyes and also with MPV. MPV is 100% aware of the display's refresh rate, and will dynamically get updates to that information as its window moves between the two displays.)

I DO NOT get VRR, because (last I checked) kwin on xorg doesn't support that.

I wonder how many folks who think that this stuff doesn't work are on Nvidia hardware. (Which (by the sound of it) doesn't work all THAT much better on Wayland.) I also wonder how many are on AMD/ATI hardware and don't know about the 'TearFree' option.

X11 doesn't do it. I did it. X11 would be tearing til the cows come home if I didn't intervene. I'm glad MPV is well-behaved but not nearly every application is. I can't get smooth motion in many applications on my machine because my main display running at 59.95 will hitch regularly as it lags behind the 60Hz secondary monitor.

Even you had to manually configure your system not to tear uncontrollably with a config file. Wayland isn't as mature as X11, sure, and the lack of color management (sorta) is a critical and fatal flaw, but it doesn't have these foundational issues that need to be worked around manually by the user on every system 20 years after every other display stack on the planet figured this all out.

X11 is mature and workable but it's not good. And it often shows the decades of mud its codebase has been dragged through. I'll be thrilled when Wayland matures and when Nvidia finally pulls its head out of its butt.

mpv is the tool I used to demonstrate that software running in xorg has access to the screen's refresh rate... and that mixed-refresh-rate screens obviously work fine in xorg. ALL of the software I use is tear-free on ALL of my installed displays, not just mpv.

> Even you had to manually configure your system not to tear uncontrollably with a config file.

The __entire point__ of `/etc/X11/xorg.conf.d/` is so that both distros and users can put configuration snippets in there to configure behavior for whatever hardware is currently installed. I use Gentoo Linux- a distro that requires that you supply your own batteries, so I supply my own config files.

> I can't get smooth motion in many applications on my machine because [I'm using NVIDIA hardware and have displays with unmatched refresh rates.]

> I'll be thrilled when ... Nvidia finally pulls its head out of its butt.

NVIDIA is okay if you're doing one of the very few things they expect you to. If you want to do most other things (like suchas have multiple displays attached to your video card that don't have exactly the same refresh rate) they are terrible. NVIDIA regularly goes off and does their own thing (usually very poorly), rather than use the thing that everyone else developed that works well.

The NVIDIA-on-Linux situation has been bad for at least twenty years. Torvalds' now-eleven-year-old "[NVIDIA is] the single worst company we [Linux developers] have ever dealt with ... NVIDIA: FUCK YOU!" remark [0] was motivated by legitimate, long-standing complaints that have yet to be resolved.

If you're using an NVIDIA card on Linux, and you're using it as a graphics display or 3D accelerator card (rather than -say- CUDA and friends) you're deliberately and enthusiastically plunging your hand and whole arm into a bag of sharp knives. It's not going to get notably better because it hasn't gotten better in the last 20+ years.

[0] https://www.phoronix.com/news/MTEyMTc

I expect a lot of digital signage is running through a browser engine these days, like everything else. Who would be targeting raw OpenGL surfaces these days?

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