xrandr dual-screen usability survery (Was: Dual-head config broke with update to 1.4.2)

Alex Deucher alexdeucher at gmail.com
Wed Feb 17 07:35:37 PST 2010

On Wed, Feb 17, 2010 at 9:45 AM, Martin Cracauer <cracauer at cons.org> wrote:
> Here are the results of my quick survey of Window Managers present in
> Debian/Stable.  That is the same Debian that has the Xorg server with
> classic dualhead effectively removed.
> The goal is to see how practical xrandr is for dual-screen purposes,
> today.
> I started the X11 server with 1400x1050 on the internal LCD of my
> Thinkpad and then added a monitor on the VGA port via randr.
> fvwm2: completely broken, cannot even get keyboard focus to the second
> screen, although you can move clients there with the mouse.
> Enlightenment only has E16 in Debian/stable.  I will compile E17 later
> to see whether it has virtual desktop support with xrandr but I did
> give E16 a spin.  Entirely broken.  The second desktop cannot pan, so
> you never get to see the WM bars at the bottom.  There is graphical
> corruption when moving windows (leaves the "trace") and graphical
> corruption from some other action I didn't identify (black goo under
> top bar).  I took photos in case you want to see.
> GNOME and KDE are behaving the same: kinda works but as expected it
> has no support for individual virtual desktop switching (yet?).
> But there are problems with GNOME/KDE even if you accept the lack of
> virtual desktops.  Just opening GIMP in the xrandr'ed X11 server under
> GNOME makes GIMP come up half on the left screen and half on the right
> screen (photo available).  It even has single dialog boxes that are
> obviously hardcoded to open in the middle of what GIMP thinks is "the
> display", and that means it has a dialog box coming up between the
> screens with the "yepp" buttom on the main screen on the "nah" on the
> second screen.  I assume this is the same as if you had used Xinerama,
> and it is one other major reason why I used individual displays for
> dual-head, and never used Xinerama.

What version of GONE/KDE did you test?  If it's as old as your xserver
it may not support xinerama hints.  All recent versions from the last
few years support xinerama hints and handle window and dialog message
placement appropriately on multi-head displays.

> Even outside of GIMP problems there's more trouble when running KDE
> and GNOME, namely that the second screen doesn't pan so you can never
> reach (or read) the bottom taskbar.  That works just fine in classic
> dualhead.
> I also noticed that even GNOME's internal dialogs are confused.  For
> example, the battery status pop-up indicator for battery status comes
> up half on the left and half on the right display.
> Compiz: broken, hangs.  No idea whether that's due to the xrandr or
> something else.

Compiz requires 3D support, you'd need to make sure that is enabled.

> Anyway...
> It looks to me like removing classic dualhead has been done way ahead
> of time.  The above is certainly not usable for dual-screen setups the
> way I and people I know get their work done, and annoying for many
> other people, witness the GIMP misbehavior.

No one removed zaphod support.  As I've said several times, we've
attempted to keep the feature alive (in fact I think radeon is the
only xrandr capable driver that does), but in some cases, like yours,
the wrong outputs get selected.  What I've said again and again is
that it's not a priority for us developers to fix this for all cases.
It should not be too hard to fix the driver to select which head you
want to use for zaphod mode, I just don't have the time at the moment.
 If you want to have a crack at it, I'm happy to point you in the
right direction.

> I originally thought that KDE/GNOME might work well enough if you
> accept the lack of individual virtual desktop switching, but it is
> just not the case.  Just GIMP is basically confused to the point of
> unusability and if I used GNOME or KDE - how am I supposed to live
> without the bottom taskbar? And that's after me only trying GIMP, who
> knows which other multi-window programs are broken.
> In any case, myself I am not willing to live without individual
> virtual desktop switching in the first place.  There's a reason why I
> picked a Unix over Windows, and that is that vendor's can't easily
> decide that "my" features without me being able to fight back.
> Overall my original impression has been reinforced: you basically
> dropped what hackers need when getting work done on a desktop Unix
> machine in favor of what managerish types coming from Windows need
> when standing in front of a projector and need to get their
> single-task thing done.
> Before I pass final verdict, what would be involved in -say- hacking
> up fvwm2 to deal with xrandr?

I think you are confused.  Most window managers already deal properly
with xrandr.  xrandr provides xinerama hints as to the geometry of the
heads so that window managers can place windows appropriately.  What
you are trying to implement is head specific desktop switching which
has nothing to do with xrandr.


> Martin
> --
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> Martin Cracauer <cracauer at cons.org>   http://www.cons.org/cracauer/
> FreeBSD - where you want to go, today.      http://www.freebsd.org/
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