nomultiplemonitors does not work in windowed mode

Fri Jul 1 15:28:00 GMT 2011

On 30/06/2011 21:48, szalai endre wrote:
>>> This mode automatically sets the multiplemonitors option and it cannot
>>> be overriden from command line.
>> What is it that makes you think this?
> According to XWin docs: "-[no]multimonitors or -[no]multiplemonitors Create
> a screen 0 that covers all monitors [the primary monitor] on a system with
> multiple monitors. This option is currently enabled by default in
> -multiwindow mode."

"enabled by default" is not the same as "cannot be disabled from the command
line", which is what -nomultiplemonitors does.


> And this is exactly what happens. When I start a program, it shows up on
> both monitors (half here, half there). This is not supposed to happen (see
> next point).
>> I'm not sure if I understand what you are expecting to happen with
>> -multiwindow -nomultiplemonitors:
> I have 2 monitors. Imagine you turn off one of them and you want to use the
> other one only.

I assume that is because one of them in an external monitor attached to a
laptop which you now want to use on the move, or something like that.  This is
an interesting use case which hadn't occurred to me previously.

If that is the case, it might be that using -resize=randr is a better
approach, as this allows the X server to use both monitors for the X display
when they are attached, and then resize the X display to the primary monitor
when the secondary is detached.

(Note that this isn't something I've tested and I wouldn't be surprised if
there were some problems with doing that, like for e.g. the windows not
getting automatically moved onto the primary display when the resize occurs)

Or maybe you don't like the fact that the X windows appear centered on the
virtual desktop, and thus split between monitors?  Fixing this has been on the
todo list for some time, unfortunately.

> Currently, Cygwin-X will span over all monitors - unless
> you use the multiplemonitors option. I think the goal for this option is
> very clear from the docs: use only 1 monitor for the root window, no matter
> what. So I would expect this behavior: you should not be able to move off
> windows from the primary monitor, at all. The point is, you want to limit
> the root window to one monitor only.
> I see the -multiwindow and -nomultiplemonitors options completely
> independent from each other. They should not have any relationship at all.
> The first just tells how you want to map windows within the root window,
> while the other simply specifies how many monitors you want to use for the
> root window.

... and indeed they are.

But if you actually try -multiwindow -nomultiplemonitors, you'll see that the
windows can be moved off the primary monitor, but that they don't get their
contents redrawn when you do so (because the underlying X screen is only the
size of the primary monitor, so the window is effectively 'off-screen' when
moved there)

> I thought it is very clear from the docs, however your questions make me
> uncertain. Isn't is supposed to work like that?

Well, it might be obvious, but it seems we need some special case behavior
(like constraining the movement of windows, which doesn't exist yet) to behave
in the 'obvious' way in this uncommon case.

Volunteer Cygwin/X X Server maintainer

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