In KDE Plasma, System Settings, Display and Monitor there is an option called Screen tearing. It can be allowed in fullscreen windows or not and it reduces latency with most displays. Allegedly.
What does it mean it reduces latency? Which latency? Is it how fast the signal travels from the graphics card to the monitor? Does it really work? How does it work?
Any explanation or link to one helps.
Thank you! : )
https://www.displayninja.com/what-is-screen-tearing/
Screen tearing occurs when your monitor’s refresh rate and GPU’s frame rate are not synchronized. It’s characterized as a horizontal split at one or more places in the image.
[...]
It [VSync] synchronizes the vertical refresh rate of your monitor with the GPU’s frame rates, but because it makes your graphics card wait until the monitor can display a full frame, you get higher input lag.
Might not be exactly VSync they're talking about, but a similar principle will apply.
Right. I actually know what screen tearing is. I was wondering if the System Settings option could be something different. I guess it's not.
This option was enabled by default. Why would I want it enabled? : )
Content is displayed on your monitor as a series of frames. These frames are usually talked about as FPS (Frames Per Second) as a performance metric for what a system is capable of in a given game. Monitors have their own refresh rates measured in Hertz, 60Hz is the old standard rate while modern gaming monitors are 120, 144hz or higher.
Frame tearing occurs when your GPU and display are not in sync. It does not matter that your GPU is providing more or less frames than that of your monitors refresh rate but when that number is not a multiple of your monitors refresh rate tearing occurs.
Here is a simulated example of what bad frame tearing can look like:
https://en.wikipedia.org/wiki/Screen_tearing#/media/File:Tearing_(simulated).jpg
Note that frame would exist on screen for a split second.
Games often include vsync as a software option to eliminate screen tearing. Unfortunately this creates latency noticed by users as input lag because there is a delay between your action or that of a competitor being taken and what is appearing on screen because it wants to keep things in sync more than it cares about providing the latest frame as quickly as possible. Some people are very sensitive to this and it can feel very jarring / sluggish and in competitive games you are at a disadvantage.
Wayland was designed to be frame perfect, so it is like having vsync on all the time. The option in Plasma's settings is to allow screen tearing in fullscreen applications only which is how most people run games. Without this option enabled users could not disable vsync in a game.
Thank you @Staudey and @Harvey. I understand now. I know what screen tearing is, I know what fps and refresh rates are but I did not know the purpose of that option. Now I do. So it is there (in Wayland only?) so I have the option of disabling vsync in games.
Since I'm limiting my fps (to 30) (through MangoHud) anyway I'm going to disable that.
I'm not bothered by how things run. I used to be when I was running games in X11 but it feels different in Wayland, it feels smoother.
Anyway, thank you again for answering such a newbish question! : )
There is not really a reason to disable it. Having it enabled does not cause frame tearing it simply allows a application/game to request a state in which frame tearing could become possible, i.e a game can turn vsync off.
With this option in Plasma's system settings disabled you are saying I don't care what the game requests, enforce vsync always. Which doesn't really make sense to me as why wouldn't you want your games settings to be obeyed and vsync is usually on by default in games anyway.
Of course you can choose to disable it if you wish but its important that anyone reading along understand why that is not recommended / could have unexpected consequences in future especially if one forgets they disabled this setting.
Yes @Harvey, you are correct.
It's just that.. I have OCD, I have to set things in a certain way. Basically, when it comes to system settings if I'm not using it then I will set it to off. I'm sorry, I don't know if this makes sense. I don't expect anyone to understand, it's just.. how my brain works.
But thank you for the explanation! That was thoughtful. : )
