Add monitor number flag

[blkmlk]

Hi,

I think it would be great to be able to specify an output name or a monitor number to run x11docker in fullscreen mode with the monitor's size. I found it really useful for me because I use two monitors. Xephyr has the "output" flag which allows us to pass a specific monitor but I'm not sure about other X servers.

Thanks.

[mviereck]

I am not sure how to implement this.
I found that normally the fullscreen window appears on the monitor where the command is executed, e.g. in a terminal emulator. But that likely depends on the window manager (here xfwm4).
Also there is no comparable --output option for weston or nxagent. And even for Xephyr it might fail in a Wayland/Xwayland environment.

Maybe I could implement an option--xopt that allows to add arbitrary options to the X server command.

[blkmlk]

Yes, I expected that won't be applicable for other servers but I think it might be really useful for other users who have several monitors

[mviereck]

I've added an experimental option --xopt in e205f48 .

Something like this should work:

x11docker --xephyr --xopt="-output VGA-2" [...]

However, my own attempts result in a segmentation fault of Xephyr. Did you try out option -output with Xephyr?

Edit: Just found that I can avoid the segmentation fault with x11docker option --fullscreen. Otherwise x11docker sets option -screen XxY that results in less memory allocation. So you need:

x11docker --xephyr --xopt="-output VGA-2" --fullscreen [...]

[blkmlk]

It works the same way as before. To make it using -output flag we have to remove -fullscreen flag.

Edit: I mean Xephyr's "-fullscreen" flag

[mviereck]

I've made a fix in x11docker that does not set a screen size if --xopt contains Xephyr option -output.
Now I don't get segfaults and can just run:

x11docker --xephyr --xopt="-output eDP" [...]

eDP is my laptop monitor, replace with your intended monitor.
Can you please try out if it works for you?