Bug 491244

SUMMARY
When monitors wake up from power saving state, various applications will display blurry text and other elements, and have other graphical degradation, such as noticeable judder/video smoothness issues, in addition to believing that they are displaying on a lower resolution screen. 

The actual size of the elements remains correct though, respecting the system scaling settings.

This bug applies to wayland sessions when 4k displays are set to 2x scaling factor. I'm currently running two displays. The display issues have been happening consistently for a while now, but it only clicked what was going on, and how to fix it, a couple of days ago. Also, I'm running on the nvidia 555 driver, though I'm also not sure if that is a requirement either.

STEPS TO REPRODUCE
*0a.* Run mpv in the vo=gpu-next, gpu-context=waylandvk mode. Maximize and press Shift+i to toggle the info view mode and observe that it reports the display as running at 3480x2160

*0b.* Run Google Chrome (I'm running chrome dev), set to use wayland mode and vulkan mode via the Preferred Ozone Platform option set to wayland, and the Default ANGLE Vulkan flag set to enabled via chrome://flags. Observe that the text appears crisp and hi-dpi-ish generally speaking

*1.* Let a 4K monitor with 2x scaling go to sleep via power saving mode (in my case, two of them)
*2.* Reawaken the monitors by moving a mouse
*3.* Go back to you MPV video, maximize it again, and toggle the info view on again via Shift+i. It will now report that it is running at 1920x1080, and there will be playback issues
*4.* Go to you still-running google chrome window, observe that text and other elements are now noticeably blurred
*5.* Enter chrome://restart in the url bar, and observe that text etc. will return to the proper display after restarting.
*6.* Similarly, close and then start MPV again, and observe that the Shift+i info panel now reports that the display is 3480x2160 again

OBSERVED RESULT
Text and other elements are displayed poorly, in a blurry way, and mpv video playback may have some judder and poor playback quality, until each affected application is restarted

EXPECTED RESULT
The applications correctly see that they are running at 4k resolution, don't display things in a blurry way, and otherwise continue to display things correctly without the need to restart them.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Manjaro Unstable (so, basically arch), 6.9.12-1-MANJARO (64-bit)
KDE Plasma Version: 6.1.3
KDE Frameworks Version: 6.4.0
Qt Version: 6.7.2

ADDITIONAL INFORMATION
Latest nvidia 555 driver installed, running two 4k OLED screens via an RTX 3090 (the machine has two RTX 3090s installed, with an nvlink bridge)
Intel i9-13900K
Wayland session, with as many wayland-ey things enabled as possible
Both displays are attached via HDMI 2.1 cables, with VRR disabled, 4k at 2.0 scaling factor, HDR enabled, refresh rate set to 120Hz, and VRR/G-Sync disabled on the screen's built in settings as well.