mate-display-properties: layout arrangement area has graphcial defects - usability issue

[ZebulonGlitch]

Disclaimer: I hope this is the right project to post this in. I could not for the life of me figure out what project is responsible for the binary "mate-display-properties"

Expected behaviour

When re-arranging the monitors relative to each other, in the little preview area, you should be able to clearly see the layout and adjust how your screens are positioned.

Actual behaviour

When clicking and dragging the screens, a trail of after-images is left behind, making it quite hard to see what one is doing. Separately, it sometimes happens that when working on the screens (3 displays in my case) one might be off the edge of the little preview window and hard to see/access. The only way to recenter or clear the visual artifacts is to restart the app.

The code that governs the "DRAG" action behavior is not correctly clearing the past positions of the little display objects. Also there is no "scroll" widget so if things get nudged out of the preview area you're stuffed and must restart the applet.

FYI: It's been doing this on 3 laptops for 6-7 years so it's not new. Common thread: they've all been Thinkpads with Nvidia graphics running Mint Mate. I finally got fed-up and came to see if a bug was raised- i could not find one so am writing here.

Steps to reproduce the behaviour

Open "Displays" (mate-display-properties) and in the "monitor preference" dialog, drag the displays around. It leaves a messy trail - always has in my experience.

MATE general version

1.26.0 (but it has been doing this for ~6-7 years.)

Package version

Same 1.26.0

Linux Distribution

Mint 21 Vanessa (bug has existed since perhaps Mint 17 (2015/2016)

Link to bugreport of your Distribution (requirement)

Requirement? I have searched all the Mint bug report areas - this issue seems clearly restricted to the Mate provided binary:
mate-display-properties

[lukefromdc]

This is another redraw issue and not the first time it has come up with the display applet. I've never been able to duplicate this in any of the previous times this has come up, wondering if this is ONLY with nvidia graphics. Pretty sure this capplet in mate-control-center and panel tray icon comes from xrandr in mate-settings-daemon but away from my desktop at the moment. Also at the moment my spare monitor is packed away and buried under a bunch of stuff

[CChiappa]

I see this as well on at least 2 machines - a Thinkpad T480 with NVidia graphics, but also on a T590 that only has Intel, so it is not NVidia-specific.

[lukefromdc]

At any rate, none of my setups can duplicate this. Wonder what is different if not the GPU driver?

[raveit65]

Old issue. can be fixed in themes.

foo-scroll-area:selected,
foo-scroll-area:selected:focus,
foo-scroll-area:selected:backdrop {
	background-color: @theme_selected_bg_color;
}

From https://github.com/mate-desktop/mate-themes/blob/master/desktop-themes/Blue-Submarine/gtk-3.0/mate-applications.css#L1472

Or add this snip-set to your ~.config/gtk-3.0/gtk.css and reload theme.