[systemsettings] [Bug 322482] New: Virtual screen set too large when two monitors have different rotations

[Bogdan]

https://bugs.kde.org/show_bug.cgi?id=322482

            Bug ID: 322482
           Summary: Virtual screen set too large when two monitors have
                    different rotations
    Classification: Unclassified
           Product: systemsettings
           Version: unspecified
          Platform: Other
                OS: Linux
            Status: UNCONFIRMED
          Severity: minor
          Priority: NOR
         Component: kcm_randr
          Assignee: unassigned-bugs at kde.org
          Reporter: bogdanb at gmail.com
                CC: hbock at providence.edu

KDE version: 4.8.4

In some situations (it depends from which configuration you started from), when
you combine two identical displays in one virtual screen, but you use different
orientations for each, the virtual screen is set to be too wide, in fact
exactly as wide as if both monitors had the same orientation.

Reproducible: Always

Steps to Reproduce:
1. Get a computer with two identical monitor. (Note: they probably don’t need
to be identical, but that’s the configuration I tested.)
2. Use the Size & Orientation config applet to set one of the screens to the
side of the other, both in landscape mode; apply and accept the resulting
configuration.
3. Then use the same applet to turn *just* the screen on the right to portrait
mode; again, apply and accept the resulting configuration.
4a. Move the mouse out of the right edge of the virtual screen; or,
4b. Use xrandr to check the exact configuration that was set.
Actual Results:  
4: The desktops will pan to the right, indicating that the virtual screen is
too large.

4b: The width of the virtual screen is set to the sum of the two monitors’
widths *without rotation*. In my case, it’s 3840 = 1920*2 rather than 3120 =
1920 + 1200.

Expected Results:  
The virtual screen should be set to the bounding rectangle of the two screens
in the chosen orientation. This means that (4a) the desktop shouldn’t pan and
(4b) the width of the virtual screen should be the width of the normal monitor
plus the original height of the rotated one.

I’ll attach screenshots of the resulting configuration, it’s easier to see than
to understand the written explanation. I’m not sure if it matters which screen
is considered “primary”; check the screenshot (which includes the config panel
window) to see my exact configuration.

Note that the correct configuration can be achieved using xrandr directly. Once
you do that, some modifications using the config applet retain the correct
virtual screen size, others don’t. The only consistent rule I saw is that if
you rotate the displays back to normal and apply, then rotate again one of the
screens, the bug manifests again.

Here’s the output of xrandr with the configuration set by the config applet:

$ xrandr 
Screen 0: minimum 8 x 8, current 3840 x 1920, maximum 8192 x 8192
DVI-I-0 disconnected (normal left inverted right x axis y axis)
VGA-0 disconnected (normal left inverted right x axis y axis)
DVI-I-1 connected 1200x1920+1920+0 left (normal left inverted right x axis y
axis) 546mm x 352mm
   1920x1200      60.0*+   59.9  
[snip other modes]
HDMI-0 connected 1920x1200+0+430 (normal left inverted right x axis y axis)
546mm x 352mm
   1920x1200      60.0*+
[snip other modes]

And here’s how to fix it and what it should actually look like:

$ xrandr --screen 0 --fb 3120x1920
$ xrandr                                                                        
Screen 0: minimum 8 x 8, current 3120 x 1920, maximum 8192 x 8192               
DVI-I-0 disconnected (normal left inverted right x axis y axis)                 
VGA-0 disconnected (normal left inverted right x axis y axis)                   
DVI-I-1 connected 1200x1920+1920+0 left (normal left inverted right x axis y
axis) 546mm x 352mm                                   
   1920x1200      60.0*+   59.9                                                 
[snip other modes]
HDMI-0 connected 1920x1200+0+430 (normal left inverted right x axis y axis)
546mm x 352mm                                          
   1920x1200      60.0*+
[snip other modes]

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