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#1 2020-04-02 02:37:57

Roger
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From: Vancouver, BC, Canada
Registered: 2019-04-06
Posts: 47  
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X11 background flickers on wide screens

I wonder if this is a general problem, or is related to specific monitors. I run X11 with the fvwm window manager, and have used the traditional "grey" X11 background on the root window; it is in fact a checkerboard mosaic using very small black and white squares. When I replaced a 16x10 display with a 16x9 replacement the far right area of the screen displayed an undulating background with wave-like horizontal lines. When a window was located in that area its contents displayed normally.

I am now setting up a new computer, and the 16x9 display exhibits exactly the same glitch. Anything displayed in that area is rendered properly, and if I use "xsetroot -solid <somecolour>" there is no problem. Since this happens with two monitors, of different vintage, I wonder if it is in fact an X11 problem, and there is something wrong with the rendering of the checkerboard pattern. I note that X11 changed the default background a couple of upgrades ago.

It is not of any great significance, as I have discovered that I prefer the solid background, and if it has to be grey, there are several shades available.

Anyone else have the same experience?

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#2 2020-04-04 04:26:31

Roger
Member
From: Vancouver, BC, Canada
Registered: 2019-04-06
Posts: 47  
Website

Re: X11 background flickers on wide screens

Sorry for  the delay, as I have been busy handling the video again for the beowulf upgrade. The video card is GT440 1G from Nvidia and does not work properly without the Nvidia specific driver. That was a lot of trouble eight years ago when the machines were new, but the driver became a standard package from Debian, and now Devuan; it requires compilation of a kernel module each time there is a kernel upgrade. I didn't make any comment about inches (and as a Canadian I would prefer to use centimetres :-) The problem seems to depend on the screen aspect ratio, and showed up on one computer when its monitor gave up and was replaced with a newer one, having the wider 16x9 aspect ratio. The cables and connections are the standard that came with a usual desktop (tower) computer. I just got a new computer with Intel B360M on board graphics and it shows the same behaviour. The only problem is with the traditional X11 background, so-called grey but actually a checkerboard; all other graphics display perfectly. I suspect there is a problem with the X11 background, and maybe that is why they replaced it; it is no longer the default.

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#3 2020-04-04 16:57:11

Roger
Member
From: Vancouver, BC, Canada
Registered: 2019-04-06
Posts: 47  
Website

Re: X11 background flickers on wide screens

The problem occurs on two computers with different graphics cards and monitors by different manufacturers. It only appeared on the older nvidia machine when the 16x10 monitor was replaced by one that was 16/9. It appeared on the brand new machine with onboard Intel graphics immediately. The problem ONLY occurs using the old X11 "grey" background; that is the common feature, and I assume it is the problem. In both cases I did the setup, one eight years ago and the other just recently, by letting xorg do its hardware checking, and in the more recent case it runs without an xorg.conf file. The new 16/9 monitor displays beautiful detailed graphic output over the whole screen area for all applications, so I have had no reason do do any BIOS adjustment.

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