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dominbdg avatar Ubuntu

Ubuntu 20.04 with KDE - issue with resize to FullScreen

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dominbdg

I'm using a laptop with Full HD resolution, but sometimes I need the resolution to be lower.

When I try to change it using the following command:

xrandr -s 1440x900

the result is not what I expect. It's not scaled to full-screen. The picture covers only a square area with black spaces on left and right.

Is it possible to change resolution and force extend lower resolutions to fullscreen?

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matigo
FullHD (1920x1080) and WXGA+ (1440x900) operate at different aspect ratios. Having the lower resolution fill the screen would stretch characters and images horizontally by 8%, reducing readability and contributing to eye strain. Is this something you want to do?
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dominbdg avatar
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dominbdg
I would like to have the same as I have with extended monitor - when I change screen on extended monitor I have it on fullscreen and on my laptop I have lower resolution on not fullscreen. I would like to have other resolutions on fullscreen also.
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Nate T avatar Ubuntu
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Nate T

tl;dr / Short answer:

Rerun the command that you listed, but swap 1440 for 2560. If it is still a bit smaller on all sides, replace -s option with --scalefrom. That should fix. To go back to original pixel dimensions, run:

xrandr --preferred

An alternate solution

You can fill out the sides by incrementing the first number (1440 for you) little by little, in iterations, until it fits correctly. You can also decrease the second (900) little by little in the same fashion. The effect on the black spots will be the same for both methods, however, the effect on the resolution will be the opposite. To keep it (about) the same res, switch back and forth.

Also, as matigo said, you have switched your aspect ratio. That is what I am reffering to in the section below when I say that WxH needs to stay the same. This solution should put them somewhere close.

Full answer:

To get full screen, Your proportions need to be the same as those of the screen.

When you run:

xrandr -s 1440x900

with the -s command, you are not setting the resolution. You are setting the screen size. It uses pixels as an option, but..

Assuming no auto-rescale

..making the HxW larger will not make a pixel smaller. It will just make the actual size at which it tries to draw your screen bigger.. and vice versa in the opposite direction. This is the reason that the --scale option is included. You could double both H and W, which would keep the proportions, but would leave it double the required size. Running

xrandr--scale 0.5

​ would then bring it back with 2X resolution, if the hardware supports it. Also, running:

xrandr

with no options should show you what mode your screen prefers. This is the size that should result from the --preferred option.

​If one dimension is correct and the other is too small, it means you didn't use an appropriate proportions (the aspect ratio). Basically, dividing the first number by the second number will be the same for every possible set of "perfect" dimensions. This is how I got the number 810. I did the following:

1080/1920*1440 = the best W for `H == 900`
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dominbdg avatar
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dominbdg
Hello, Thanks a lot for very comprehesiv explanation, Yes, You right - I was in wrong thinked that using xradr -s 1440x900 and all will be bigger. Currently xrandr --scale -> looks like resolved my issue.
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Nate T avatar
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Nate T
If it helped, consider accepting, so others in the future who have the same issue and find this page via search will know it is worth implementing. Glad I could help.
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dominbdg avatar
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dominbdg
what do You mean - accepting ?
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Nate T avatar
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Nate T
you click underneath the vote arrows beside the answer that helped you / answered your question. This keeps it at the top and lets future readers know that the answer is helpful. It also rewards the answerer with rep.
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