Background corruption when changing screen layout

[phocean]

Expected behaviour

The background geometry should get automatically adapted to any screen layout change (number of external screens, of various resolutions and orientations).

Actual behaviour

When Mate is responsible of handling the desktop drawing, some corruption may happen.

Here is the wallapaper setting:

Here is what happens when an external screen is plugged in or out:

Steps to reproduce the behavior

1. Disable Caja handling wallpaper ("don't show desktop icons setting") so that it is handled by mate-session

2. Plug in an external monitor and observe wallpaper corruption (generally on the external screen)

3. Plug out the external monitor and observe how corruption is still present on primary screen (it is not possible to recover a clean state)

4. A way to recover a clean wallpaper geometry is to simply open the background tab in Appearance.

Possible workaround

There is no issue when Caja draws the desktop, but this is not a desired setting in my case.

MATE general version

1.20.1 as in Ubuntu 18.04.

[raveit65]

What kind of monitors are you using?
Was this working before with older MATE versions?

[phocean]

They are connected through DP and HDMI ports.

Any combination (one or two external monitor on any interface) of any screen model (it also happen at my work place with different screen models and resolutions) would cause some corruption.

If it helps, here is the xrandr output with the full layout:

xrandr.txt

Screens are DELL U2515H and EIZO EV2450.

[phocean]

And sorry, I cannot reply on previous versions as I am a new user :-)

But testing with an old live ISO is definitely something I could do if it helps.

[raveit65]

In other words it is a fresh installation of ubuntu-18.04 ?
And you are using non-HIDPI resolutions and HIDPI resolutions?
@flexiondotorg
Please help out, this is ubuntu distro...

[phocean]

Yes, it is a fresh install of Ubuntu 18.04, so I would be surprised if it cannot be reproduced on any setup with a dual screen.

At office none of my screen is HDPI (1920x1080). And here one of them is not (also 1920x1080).

[raveit65]

Ok, you're speaking about 2 systems and each system has 2 monitors?
One system use 2 monitors (non-HiDPI)?
The other system use a HiDPI monitor and a non-HiDPI monitor?

[phocean]

No, it is my laptop moving between places, so same system, same issue.

[raveit65]

Well, every box has different hardware, for this reasons i ask you for more infos.
My setup:
normal powerful PC with nvidia graphic (display port + hdmi port)

1. monitor with 3840 x 2160 px at display-port 60Hz
2. monitor with 1920 x 1200 px at hdmi-port 60 Hz

In the test i used same resolution for both 1920 x1080 (non-hidpi)

Plug in a second monitor doesn't cause any problems with desktop glitches or redraw issues.
Doesn't matter which monitor was used as primary.
Unplug a monitor can cause a weird tiling of the desktop from the other monitor.
But it isn't clear reproducible for me, cause it doesn't happen always.
It never happens if i unplug the monitor at display-port.
Unplug the monitor at hdmi-port can cause the issue, but not constantly.

With that command i was able to redraw the desktop in worse case.
gsettings set org.mate.background background-fade false && gsettings set org.mate.background background-fade true
Put it in a script and use it as panel launcher as workaround for the moment.

PS: Using mate-display-properties to power off a second monitor gives me cleaner results.

[phocean]

The gsettings trick does not work for me, so we may not have the same issue.

You tested with "show-desktop-icons" disabled, right ? (so that caja is not taking care of the drawing).

The best workaround for me is to actually rely on caja, "show-desktop-icons" enabled.

[raveit65]

You tested with "show-desktop-icons" disabled, right ?

sure, this report is about mate-settings-daemon, not caja :)

[phocean]

Two new computers : Lenovo Thinkpad T440p (Nvidia graphics), Lenovo Yoga S730.

Fresh installs, same issue.