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Bug 773601 - Display size detected as 0x0 pixels when RANDR is not available
Display size detected as 0x0 pixels when RANDR is not available
Status: RESOLVED FIXED
Product: gtk+
Classification: Platform
Component: Backend: X11
3.22.x
Other Linux
: Normal critical
: ---
Assigned To: gtk-bugs
gtk-bugs
Depends on:
Blocks:
 
 
Reported: 2016-10-27 19:10 UTC by Michael K.
Modified: 2016-11-17 13:06 UTC
See Also:
GNOME target: ---
GNOME version: ---


Attachments
xorg.conf (2.11 KB, text/plain)
2016-10-27 19:10 UTC, Michael K.
  Details
[PATCH] gdk: Fix screen geometry detection for non-randr setups (2.42 KB, patch)
2016-11-14 23:05 UTC, Michael K.
committed Details | Review

Description Michael K. 2016-10-27 19:10:50 UTC
Created attachment 338633 [details]
xorg.conf

I have also reported this issue on Firefox's bugzilla earlier: https://bugzilla.mozilla.org/show_bug.cgi?id=1312274

I am using a Dell UP2715K, it is a 5K monitor (5120 x 2880) which is exposed as two 2560x2880 side-by-side tiles/displays.
To make sure that it is viewed by X as a single diplay I have had to set up a special xorg.conf file (attached), which uses Nvidia's "Twinview" approach and enables Xinerama (this disables X's RANDR extension, so this ensures that X and applications do not see the separate tiles, only the whole display).

GTK inspector reports:
Monitor 0:
  Geometry 0x0@2 at 0,0
  Size 605 x 340 mm2

Google Chrome and QT apps do not seem to have this problem.

The XINERAMA extension does not seem to be actually working as xdpyinfo reports (see below), but the display resolution is reported properly. This must be a peculiarity of how Nvidia driver works. The point of enabling Xinerama is to prevent the driver from exposing screen tiles as two separate displays. (I've found this solution somewhere while googling for a suitable configuration for my display)

Here is an excerpt from /var/log/Xorg.0.log:
[     8.499] (WW) NVIDIA: The Composite and Xinerama extensions are both enabled, which
[     8.499] (WW) NVIDIA:     is an unsupported configuration.  The driver will continue
[     8.499] (WW) NVIDIA:     to load, but may behave strangely.
[     8.499] (WW) NVIDIA: Xinerama is enabled, so RandR has likely been disabled by the
[     8.499] (WW) NVIDIA:     X server.

$ xdpyinfo -ext XINERAMA
name of display:    :0
version number:    11.0
vendor string:    The X.Org Foundation
vendor release number:    11804000
X.Org version: 1.18.4
maximum request size:  16777212 bytes
motion buffer size:  256
bitmap unit, bit order, padding:    32, LSBFirst, 32
image byte order:    LSBFirst
number of supported pixmap formats:    7
supported pixmap formats:
    depth 1, bits_per_pixel 1, scanline_pad 32
    depth 4, bits_per_pixel 8, scanline_pad 32
    depth 8, bits_per_pixel 8, scanline_pad 32
    depth 15, bits_per_pixel 16, scanline_pad 32
    depth 16, bits_per_pixel 16, scanline_pad 32
    depth 24, bits_per_pixel 32, scanline_pad 32
    depth 32, bits_per_pixel 32, scanline_pad 32
keycode range:    minimum 8, maximum 255
focus:  window 0x2e00071, revert to PointerRoot
number of extensions:    27
    BIG-REQUESTS
    Composite
    DAMAGE
    DOUBLE-BUFFER
    DPMS
    DRI2
    GLX
    Generic Event Extension
    MIT-SCREEN-SAVER
    MIT-SHM
    NV-CONTROL
    NV-GLX
    Present
    RECORD
    RENDER
    SECURITY
    SHAPE
    SYNC
    X-Resource
    XC-MISC
    XFIXES
    XFree86-DGA
    XFree86-VidModeExtension
    XInputExtension
    XKEYBOARD
    XTEST
    XVideo
default screen number:    0
number of screens:    1

screen #0:
  dimensions:    5120x2880 pixels (605x340 millimeters)
  resolution:    215x215 dots per inch
  depths (7):    24, 1, 4, 8, 15, 16, 32
  root window id:    0x1bd
  depth of root window:    24 planes
  number of colormaps:    minimum 1, maximum 1
  default colormap:    0x20
  default number of colormap cells:    256
  preallocated pixels:    black 0, white 16777215
  options:    backing-store WHEN MAPPED, save-unders NO
  largest cursor:    256x256
  current input event mask:    0xfac033
    KeyPressMask             KeyReleaseMask           EnterWindowMask          
    LeaveWindowMask          KeymapStateMask          ExposureMask             
    StructureNotifyMask      SubstructureNotifyMask   SubstructureRedirectMask 
    FocusChangeMask          PropertyChangeMask       ColormapChangeMask       
  number of visuals:    132
  default visual id:  0x21
  visual:
    visual id:    0x21
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x22
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x24
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x25
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x26
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x27
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x28
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x29
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x2a
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x2b
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x2c
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x2d
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x2e
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x2f
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x30
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x31
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x32
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x33
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x34
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x35
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x36
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x37
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x38
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x39
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x3a
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x3b
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x3c
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x3d
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x3e
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x3f
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x40
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x41
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x42
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x43
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x44
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x45
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x46
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x47
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x48
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x49
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x4a
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x4b
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x4c
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x4d
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x4e
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x4f
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x50
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x51
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x52
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x53
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x54
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x55
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x56
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x57
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x58
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x59
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x5a
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x5b
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x5c
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x5d
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x5e
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x5f
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x60
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x61
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x62
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x63
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x64
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x65
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x66
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x67
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x68
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x69
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x6a
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x6b
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x6c
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x6d
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x6e
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x6f
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x70
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x71
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x72
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x73
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x74
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x75
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x76
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x77
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x78
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x79
    class:    DirectColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    11 bits
  visual:
    visual id:    0x23
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x7a
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x7b
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x7c
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x7d
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x7e
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x7f
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x80
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x81
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x82
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x83
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x84
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x85
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x86
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x87
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x88
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x89
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x8a
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x8b
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x8c
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x8d
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x8e
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x8f
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x90
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x91
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x92
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x93
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x94
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x95
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x96
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x97
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x98
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x99
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x9a
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x9b
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x9c
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x9d
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x9e
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0x9f
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0xa0
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0xa1
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0xa2
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0xa3
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits
  visual:
    visual id:    0xa4
    class:    TrueColor
    depth:    32 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits

Xlib:  extension "XINERAMA" missing on display ":0".
XINERAMA extension not supported by server
Comment 1 Michael K. 2016-11-14 13:35:38 UTC
I've tried the test python script from this bug report: https://bugzilla.gnome.org/show_bug.cgi?id=772202

Here is its output:
Screen: 0x0
RootWindow: (x=0, y=0, width=2560, height=1440)
Monitor 0: 0x0+0+0 scale 2 workarea 0x0+0+0
Comment 2 Matthias Clasen 2016-11-14 19:35:22 UTC
[     8.499] (WW) NVIDIA: The Composite and Xinerama extensions are both enabled, which
[     8.499] (WW) NVIDIA:     is an unsupported configuration.  The driver will continue
[     8.499] (WW) NVIDIA:     to load, but may behave strangely.
[     8.499] (WW) NVIDIA: Xinerama is enabled, so RandR has likely been disabled by the
[     8.499] (WW) NVIDIA:     X server.

Sounds pretty clearly like an unsupported or problematic X server/driver configuration.
Comment 3 Michael K. 2016-11-14 19:41:56 UTC
* xdpyinfo detects the resolution correctly (see the output above),
* QT also detects it just fine.
Comment 4 Matthias Clasen 2016-11-14 19:45:24 UTC
we rely on randr for this information...
Comment 5 Michael K. 2016-11-14 19:50:23 UTC
There should be a fallback when randr is not available.

I am looking into fixing this myself.

There seems to be a non-randr init fuction as well (init_no_multihead()) but I guess it is broken:

In gdkscreen-x11.c:

static gboolean
init_multihead (GdkScreen *screen)
{
  gboolean any_changed = FALSE;

  if (!init_randr15 (screen, &any_changed) &&
      !init_randr13 (screen, &any_changed))
    init_no_multihead (screen, &any_changed);

  return any_changed;
}
Comment 6 Michael K. 2016-11-14 19:53:30 UTC
By the way, the odd thing is that the display size in millimeters is reported by GTK/GDK correctly:

GTK inspector reports:
Monitor 0:
  Geometry 0x0@2 at 0,0
  Size 605 x 340 mm2
Comment 7 Michael K. 2016-11-14 23:05:35 UTC
Created attachment 339843 [details] [review]
[PATCH] gdk: Fix screen geometry detection for non-randr setups
Comment 8 Michael K. 2016-11-14 23:07:31 UTC
The atatched patch fixes this issue.
Comment 9 Matthias Clasen 2016-11-17 12:53:17 UTC
Thanks for the patch!