jfabernathy
Posts: 55
Joined: Thu Oct 11, 2018 10:52 am

Desktop not fitting screen today on RP4

Sat Dec 07, 2019 10:04 pm

So this is a new problem that started today. I did a fresh install of Raspbian Buster with Desktop on my RP4. Usually after the install questions, I update to the latest and then change my screen resolution from 4K to 1080P so the screen is viewable from across the room. It's a 60" UHD 4K TV. Normally that works fine, but today the desktop extends beyond the screen so you can't see the menu bar at the top, etc. I have to leave it at 4K so I can see everything.

This has not happened before today. To confirm it's a wide spread issue I reinstalled Buster lite and then installed X and XFCE and Mate. All now have the same problem.

Never noticed this until today.

wolf.z
Posts: 131
Joined: Thu Dec 24, 2015 8:34 pm

Re: Desktop not fitting screen today on RP4

Sat Dec 07, 2019 10:56 pm

There is a underscan / overscan issue, steming from analogue video compatibility history. This legacy stuff drops in frequently.
https://www.raspberrypi.org/forums/view ... p?t=246522
Try disable_overscan=1 in config.txt first....

(mod edit for language - please keep it clean)

jfabernathy
Posts: 55
Joined: Thu Oct 11, 2018 10:52 am

Re: Desktop not fitting screen today on RP4

Tue Dec 10, 2019 10:24 am

if I disable_overscan=1 in config.txt it will bring the X11 desktop back on the screen by when video is played it also now has the black border around it. If I just use Buster, X11, Openbox and xinit I then can us xrandr to set the screen size correctly if overscan if off. But that's a lot of work when a normal XFCE4 would work nicely for me. It did last week.

6by9
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Re: Desktop not fitting screen today on RP4

Tue Dec 10, 2019 11:31 am

Overscan support wasn't available in the kernle until July. Raspbian is a moderate chunk behind the bleeding edge as stability is the key.

When had you updated previously so that we can gauge what you've updated from?
And what are you using to play back videos?

You can use xrandr to configure overscan - it's the margins parameters. That should apply to any layer that is composed using KMS. If your app uses MMAL, IL, or DispmanX to put additional layers on the screen, then those aren't through KMS, and will be using the overscan values configured in the firmware. (The firmware attempts to set the KMS margins based on the fw settings via the kernel command line).
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jfabernathy
Posts: 55
Joined: Thu Oct 11, 2018 10:52 am

Re: Desktop not fitting screen today on RP4

Tue Dec 10, 2019 11:47 am

6by9 wrote:
Tue Dec 10, 2019 11:31 am
Overscan support wasn't available in the kernle until July. Raspbian is a moderate chunk behind the bleeding edge as stability is the key.

When had you updated previously so that we can gauge what you've updated from?
And what are you using to play back videos?

You can use xrandr to configure overscan - it's the margins parameters. That should apply to any layer that is composed using KMS. If your app uses MMAL, IL, or DispmanX to put additional layers on the screen, then those aren't through KMS, and will be using the overscan values configured in the firmware. (The firmware attempts to set the KMS margins based on the fw settings via the kernel command line).
My install was based on 2019-09-26-raspbian-buster and updated this week. I've tried several options:
1. full RPD desktop with overscan off so on 4K TV, the screen is full and proper until I use screen configuration to change to 1080p.
2. Raspbian lite with X, Mate, lightdm. Same as #1
3. Raspbian lite with X, Openbox and xinit. xrandr was used to set the screen to 1080p. Since I don't have a desktop I can't say for sure what happens, but my application GUI and video play look proper on the screen when running. in this case it's Mythtv frontend.

I can use #3, but a full RPD system is more convenient and it doesn't get in my way. I've done all this since August, but last week some update changed the desktop so that changing the screen size for 4K to 1080p pushes the desktop off the screen a few characters so the menu is not readable. The 4K UHD TV and the RP4 has some compatibility issue that makes the default 3840x2160 /30 and that really messes with video playback and since all the videos are 1080i or 720p, reducing the screensize should make the performance better.

jfabernathy
Posts: 55
Joined: Thu Oct 11, 2018 10:52 am

Re: Desktop not fitting screen today on RP4

Fri Dec 13, 2019 11:48 am

Tried an experiment today. On top of the Openbox I just installed xfce4 and lightdm. When I boot up and login I get the 4K desktop but using Settings Display I can reduce it to 1080p and it works without pushing the Desktop off the screen. Something has changed or the order I did the install avoided a problem. Not sure, but now I have XFCE4 desktop with a 1080p screen on a 4K TV.

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