Same here, although in FF it tears regardless of whether fullscreen, and even with this website here. Ironically, as I was entering this comment, the whole screen got uniform tearing all over the browser window. I took a screenshot to attach, but the act of doing so fixed all the tearing. I suspect that this is because taking a screenshoot refreshes things, so the problem goes away. The problem happens maybe once an hour, seemingly at random. I will see it for a split second, for example, during scrolling, when presumably ever single window update has some tiny chance of tearing everything, but otherwise does so correctly. I don't know where in the stack between me and the hardware this problem lies.

Guys, if you don't report what graphics card you are using, I have no idea what to look for. Thanks.

Click on the image below to zoom. This is what it looks like on Intel 615 graphics, right here on Phabricator in Firefox. As you'll notice, it's a purely horizontal phenomenon, so the dividing lines between bug reports look normal while the text does not. All other windows look normal.

I think if you sit there for a few minutes slowly scrolling up and down through bug reports, you'll see it occur on a single frame, only to be fixed on the next frame.

Sorry about the late reply:

Both seem to be intel 4400 integrated, but one has an nvidia on top:

 inxi -G
Graphics:  Card-1: Intel 4th Gen Core Processor Integrated Graphics Controller
           Card-2: NVIDIA GK106M [GeForce GTX 765M]
           Display Server: X.Org 1.17.1 drivers: intel (unloaded: fbdev,vesa)
           Resolution: 1920x1080@60.0hz
           GLX Renderer: Mesa DRI Intel Haswell Mobile GLX Version: 3.0 Mesa 10.5.9

is this still a problem on for y'all on the latest firefox? thanks.

Yes. Yes it is. Intel® HD Graphics 620 (Kaby Lake GT2) Intel Iris Plus Graphics 640 (Kaby Lake GT3e) both running current build of Solus 3.26.2 Full screen tearing in Firefox Quantum 58.0. Was able to "temporarily fix" the issue with compiz but compizconfig-setting-manager not working on 620 card. ccsm reports
Missing gtk2-engine-murrine and

• Error in `/usr/bin/python': free(): invalid pointer: 0x00007f12e6aad0d8 ***

Also wallpaper gone.

inxi -G
Graphics: Card: Intel HD Graphics 620

Display Server: x11 (X.Org 1.19.6 )
drivers: modesetting (unloaded: fbdev,vesa)
Resolution: 1920x1080@60.05hz
OpenGL: renderer: Mesa DRI Intel HD Graphics 620 (Kaby Lake GT2)
version: 4.5 Mesa 17.3.3

If any other information is needed let me know. Just did the most recent update and still seeing the tearing issue only in full screen on Firefox. I've primarily noticed it in Youtube videos the most.

Thanks to bwat47 this is the fix that worked for the Intel HD Graphics 620 (Kaby Lake GT2) requiring only step 1 and the Iris Plus 640 (Kaby Lake GT3e) requiring step 1 and 2:

1. Go to budgie desktop settings > Under Appearance > Windows > turn on "Disable unredirection of windows"

2. about:config in url box Firefox

layers.acceleration.force-enabled to true

Also the fix for tearing on gnome-mpv for anyone interested (also thanks to bwat47):

gnome-mpv video player fix:
preferences > disable "Use Client Side Decoration"

Not sure if this a band-aid for a bigger problem but this did the trick for me so hope it helps someone else :)
Also seeing as how Solus 4 is on the horizon this hopefully won't be an issue in the near future with Wayland but don't quote me on that.

Yeah, the tearing happens in Firefox, because it's not using hardware acceleration on Linux by default. However, the layers.acceleration.force-enabled flag enables it and helps with tearing. I also had this problem on fresh install of Solus, but I quickly googled the solution and forgot about this problem.
Maybe we should enable HW acceleration in Solus' build of Firefox for all users?

This task could be probably be marked as solved or as a duplicate.

I still have this happening (AMD R9 380, latest update cycle), though the "fix" posted by @linuxhelmet seems to resolve things.

I have also noticed that when it happens and I bring another window to the foreground (i.e.: click another window on my second monitor) it occasionally disappears, but it's not reliable and seems more random than anything.