Only a subset of the screen is used when double DPI scaling is on

[gholms]

 * Cinnamon-Screensaver version:  4.4.1
 * Distribution:  Gentoo
 * Graphics hardware *and* driver used:  Nvidia Quadro T2000M, nvidia 440.82
 * amd64

Issue
My Thinkpad P1 has a display that runs at 3840x2160, so I run it with UI scaling set to "Double (Hi-DPI)". This doesn't seem to be getting applied to the screen saver correctly, as when it activates it fills only the upper left 25% of the screen, while the rest remains black. The text and other UI bits are the correct size; they are simply confined to a subset of the screen that has half the pixels in each dimension.

Steps to reproduce
Configure cinnamon for double UI scaling on a high-DPI screen, then trigger cinnamon-screensaver.

Expected behaviour
The screensaver should fill the entire screen.

Other information
I can provide screenshots if necessary, or logs if you can tell me how to capture them.

[icarter09]

@gholms screenshots are always helpful. If you could provide a couple, it would be greatly appreciated. Thanks.

[gholms]

Sure! I ended up taking a literal screenshot since I couldn't figure out how to do that on the affected machine while its screen was locked.

[mmirg]

I'm still seeing this issue with cinnamon-screensaver 4.8.1. I notice no other issues scaling anywhere else in the interface.

[MrPowerMac]

Still observing this on cinnamon-screensaver 5.6.2 on Gentoo. Screenshot of display settings attached.

[rimeraz]

I seem to observe the same behaviour.

• cinnamon-screensaver-5.8.0
• Distribution: Fedora 38 Cinnamon Desktop Spin
• Lenovo P14s with 14" 3840x2400 resolution
• CPU: AMD Ryzen 7 PRO 6850U with Radeon Graphics 680M, according to lshw with driver amdgpu

It only happens with a second screen attached. The lockscreen / screensaver using the laptop screen only is fine.

Screenshot of both screens together:

Photo of only the laptop screen (taken earlier):

If you need more information, I'd be happy to assist.

[rimeraz]

Sure! I ended up taking a literal screenshot since I couldn't figure out how to do that on the affected machine while its screen was locked.

I used the screenshot tool from the menu (gnome-screenshot) with capture area "screen" and 10 seconds delay. Pressed "take screenshot" and then locked the screen.

[rimeraz]

Another second screen with different resolution of 3840x2160 changes what will be shown on lockscreen / screensaver: