How to fool X to use only part of the screen?

[sitor]

Hi,

Earlier today, all of a sudden the screen of my laptop got broken. Luckily not completely. There is a vertical white band over the screen at the right side. I can still use the laptop by using only the left 70 % or so of the screen.
It is of course annoying to resize windows the whole time to the correctly working area. And for some interface elements that is not even possible. So I was hoping to be able to make X only use the left 70% or so of the screen only. That reduces my screen real estate and would give me a strange ratio but would save me a lot of trouble. But I did not find any way how to do that.

Anyone who has an idea. I'm using KDE and I'm not scared to dive into config files.

KR,

Sitor

[maat]

You can perhaps try to play with /etc/X11/xorg.conf (google for help on it) but i would'nt bet on the success of such a trial...

[sitor]

xorg.conf fiddling will probably be required, but just by trial and error, I don't think I will get far except stuck. I hoped that someone might have an idea what parameters could be changed to make X use only part of the screen.

[sitor]

I now found a good reason why I really need to dig into this: when viewing presentations, manual resizing is impossible. Same for mythtv.

[dubigrasu]

I seem to remember an application that used to do exactly that, not remember its name though...
I had a monitor with the controls broken and used that tool to adjust the image.
It was based on xrandr I believe. Probably you can use xrandr itself but I have no idea how.

[doktor5000]

krandrtray (for KDE) maybe?

[dubigrasu]

Found it, Xvidtune is the name (and not based on xrandr).

The available buttons are:
Left
Right
Up
Down
Adjust the video mode so that the display will be moved in the appropriate direction.

Wider
Narrower
Shorter
Taller
Adjust the video mode so that the display size is altered appropriately.

http://linux.die.net/man/1/xvidtune

Thing is I don't remember exactly how to use it, keeps giving me some error messages.
Anyway, worth to try it.

[sitor]

Xvidtune does not seem to work. Whatever I try it always says that what I request is not supported by my hardware. I started digging into xrandr, but that is only able to use defined modes, so I went looking into Xorg.conf. Nothing to see about the defined modes there. After some Internet searching, I found that you need to add a ModeLine in the Monitor section. Those ModeLines have a strange composition, but I found a calculator online to calculate working values at http://xtiming.sourceforge.net/cgi-bin/xtiming.pl

It calculated for me the following ModeLine:

Code: Select all

Modeline "1144x1050@75" 145.75 1144 1176 1728 1760 1050 1070 1083 1103

That indeed brings a new mode that I can select with xrandrtray or can activate that mode via xrandr command line. Problem is: it is centralized while I need it to be at the left. I have no clue how to modify it so that it uses only the left side of the screen. I tried all xrandr options, but did not find anything that does this.

Anyone?

[dubigrasu]

In my case (Nvidia graphic card) Xvidtune doesn't seem to like the proprietary driver.(doesn't work with nouveau also)
I keep getting this:

Sorry: You have requested a mode-line that is not possible, or not
supported by your hardware configuration.

It does work perfectly using nv driver though.

[sitor]

That is the same error I get. My machine has an Intel graphics card tough.

[dubigrasu]

It calculated for me the following ModeLine:

Modeline "1144x1050@75" 145.75 1144 1176 1728 1760 1050 1070 1083 1103

That indeed brings a new mode that I can select with xrandrtray or can activate that mode via xrandr command line. Problem is: it is centralized while I need it to be at the left. I have no clue how to modify it so that it uses only the left side of the screen.

Modeline "1144x1050@75" 145.75 1144 1176 1728 1760 1050 1070 1083 1103

You have to increase the values in red in order to move the screen to the left.

In this case:
1176 represents the HSyncStart value
1728 represents the HSyncEnd value

You can start Xvidtune and press the "Left" button (without applying the changes) to read the exact values you need to move the screen to the left.
Then modify the Modeline with the new values. Try different values.

That so far worked for me ( I included the modified Modeline in Xorg.conf to test the whole thing)

I wasn't able though to narrow the image.
The value in blue represent the width of the image (HTotal in Xvidtune) It also needs to be altered to narrow the image, but I haven't found a correct/working value.
(To be more exact, every time I alter this value X is going back to original settings [full-screen/centered] ignoring my modeline.)

[sitor]

Since xvidtune does not work on this machine, I have no means of getting correct values, so I tried just linear increase and decrease of the values. That dit not move the image at all however. Not sure what else I could try.

[dubigrasu]

Since xvidtune does not work on this machine

You mean the Xvidtune interface doesn't show at all?

[sitor]

Yes it does, but whatever button I touch, I get that same error

Sorry: You have requested a mode-line that is not possible, or not
supported by your hardware configuration.

[dubigrasu]

Ah, bummer...
In my case I am able to modify the values using the positional buttons (left, right, wider etc) and I can see the sliders moving.
I receive the mentioned error only when I click on "Apply".