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  1. Qt
  2. QTBUG-65457

Improper handling of TILED displays (4K / 5K / 8K etc.) / support for RandR v1.5

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Details

    • Bug
    • Resolution: Fixed
    • P2: Important
    • 6.3
    • 5.15.0
    • QPA: X11/XCB
    • None
    • OS/Distribution: Arch Linux
      Driver: Nvidia 450.57
      DM: SDDM
      WM: KDE

      Monitor: Dell UP2715K (5K tiled)
    • 9a4c98e55659b32db984612e6247ac193812a502

    Description

      There are a number of 4K and 5K monitors on the market and also lately one 8K monitor which are presented to X11 clients as two separate outputs ("tiles") due to DisplayPort bandwidth restrictions. (they are required to be connected with two cables) To handle such monitors a "monitor" concept and "TILE" property have been added to RandR since v1.5. (see for details: https://keithp.com/blogs/MST-monitors/ )

      Currently QT ignores these concepts and just deals with each output as two separate side-by-side displays. This results in all kinds of problems: e.g. two side-by-side login screens in sddm on one physical monitor, plasma panel stretches over only half of the screen, windows maximize to only one half of the screen etc.

      Gnome Mutter works with such monitors properly and so should QT. It should make use of the "monitors" concept when defined (see an example below) and treat such displays as one whole monitor rather than two separate parts.

      Relevant information:

      1. https://devtalk.nvidia.com/default/topic/1024719/unix-graphics-announcements-and-news/linux-solaris-and-freebsd-driver-387-12-beta-/

      • Tiled monitors formerly resulted in a separate Xinerama screen being reported for each tile. They will now, by default, be combined into a single large Xinerama screen.
      • The individual panels in a tiled monitor will now be arranged based on the layout information provided in the monitor's EDID. This can be overridden by either manually specifying offsets or using the "MetaModeOrientation" option.

       

       

      2. xrandr output for Dell UP2715K (5K monitor, DP-0 and DP-2 are two tiles of the same physical monitor):

      $ xrandr --listmonitors

      Monitors: 1 
0: +Auto-Monitor-4c454440b638353853 5120/600x2880/340+0+0  DP-0 DP-2

      $ xrandr 

      Screen 0: minimum 8 x 8, current 5120 x 2880, maximum 32767 x 32767 
DVI-D-0 disconnected (normal left inverted right x axis y axis) 
HDMI-0 disconnected (normal left inverted right x axis y axis) 
HDMI-1 disconnected (normal left inverted right x axis y axis) 
DP-0 connected primary 2560x2880+0+0 (normal left inverted right x axis y axis) 600mm x 340mm 
  848x480       59.74 + 
  2560x2880     59.98*   29.99   
DP-1 disconnected (normal left inverted right x axis y axis) 
DP-2 connected 2560x2880+2560+0 (normal left inverted right x axis y axis) 600mm x 340mm 
  2560x1440     59.95 + 
  3840x2160     60.00    60.00   
  2560x2880     59.98*   29.99   
  1920x1200     59.88   
  1920x1080     60.00   
  1680x1050     59.95   
  1600x1200     60.00   
  1280x1024     60.02   
  1280x800      59.81   
  1024x768      60.00   
  800x600       60.32   
  640x480       59.95    59.94   
DP-3 disconnected (normal left inverted right x axis y axis)

      $ xrandr --prop

      Screen 0: minimum 8 x 8, current 5120 x 2880, maximum 32767 x 32767 
DVI-D-0 disconnected (normal left inverted right x axis y axis) 
       CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0  
       BorderDimensions: 4  
               supported: 4 
       Border: 0 0 0 0  
               range: (0, 65535) 
       SignalFormat: TMDS  
               supported: TMDS 
       ConnectorType: DVI-D  
       ConnectorNumber: 0  
       _ConnectorLocation: 0  
HDMI-0 disconnected (normal left inverted right x axis y axis) 
       CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0  
       BorderDimensions: 4  
               supported: 4 
       Border: 0 0 0 0  
               range: (0, 65535) 
       SignalFormat: TMDS  
               supported: TMDS 
       ConnectorType: HDMI  
       ConnectorNumber: 3  
       _ConnectorLocation: 3  
HDMI-1 disconnected (normal left inverted right x axis y axis) 
       CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0  
       BorderDimensions: 4  
               supported: 4 
       Border: 0 0 0 0  
               range: (0, 65535) 
       SignalFormat: TMDS  
               supported: TMDS 
       ConnectorType: HDMI  
       ConnectorNumber: 4  
       _ConnectorLocation: 4  
DP-0 connected primary 2560x2880+0+0 (normal left inverted right x axis y axis) 600mm x 340mm 
       CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0  
       TILE: 453 1 2 1 0 0 2560 2880  
       EDID:  
               00ffffffffffff0010acb64053383538 
               1d1a0104b53c22783a7225ac5033b726 
               0b505400000001010101010101010101 
               0101010101019f0b50a030e00e103020 
               350055502100001a000000ff00334438 
               463836374a383538530a000000fc0044 
               454c4c205550323731354b0a000000fd 
               001d4b1fb436010a20202020202001a7 
               701279000012001680100000ff093f0b 
               000000000044454cb640533835380300 
               28105d0004ff099f002f801f003f0b28 
               0002000900c4bc0004ff099f002f801f 
               003f0b51000200090000000000000000 
               00000000000000000000000000000000 
               00000000000000000000000000000000 
               00000000000000000000000000007b90 
       BorderDimensions: 4  
               supported: 4 
       Border: 0 0 0 0  
               range: (0, 65535) 
       SignalFormat: DisplayPort  
               supported: DisplayPort 
       ConnectorType: DisplayPort  
       ConnectorNumber: 2  
       _ConnectorLocation: 2  
  848x480       59.74 + 
  2560x2880     59.98*   29.99   
DP-1 disconnected (normal left inverted right x axis y axis) 
       CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0  
       BorderDimensions: 4  
               supported: 4 
       Border: 0 0 0 0  
               range: (0, 65535) 
       SignalFormat: TMDS  
               supported: TMDS 
       ConnectorType: DisplayPort  
       ConnectorNumber: 2  
       _ConnectorLocation: 2  
DP-2 connected 2560x2880+2560+0 (normal left inverted right x axis y axis) 600mm x 340mm 
       CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0  
       TILE: 453 1 2 1 1 0 2560 2880  
       EDID:  
               00ffffffffffff0010acb64053383538 
               1d1a0104b53c22783a7225ac5033b726 
               0b50542108008100b300d100a9408180 
               d1c001010101565e00a0a0a029503020 
               350055502100001a000000ff00334438 
               463836374a383538530a000000fc0044 
               454c4c205550323731354b0a000000fd 
               001d4b1fb436010a20202020202002c4 
               02030cf123090707830100004dd000a0 
               f0703e805020650c555021000018565e 
               00a0a0a029503020350055502100001a 
               00000000000000000000000000000000 
               00000000000000000000000000000000 
               00000000000000000000000000000000 
               00000000000000000000000000000000 
               00000000000000000000000000000034 
               701279000012001682101000ff093f0b 
               000000000044454cb640533835380300 
               3c4cd00084ff0e9f002f801f006f083d 
               0002000400105d0004ff099f002f801f 
               003f0b280002000900c4bc0004ff099f 
               002f801f003f0b51000200090007000a 
               08810008040004021000000000000000 
               0000000000000000000000000000c590 
       BorderDimensions: 4  
               supported: 4 
       Border: 0 0 0 0  
               range: (0, 65535) 
       SignalFormat: DisplayPort  
               supported: DisplayPort 
       ConnectorType: DisplayPort  
       ConnectorNumber: 1  
       _ConnectorLocation: 1  
  2560x1440     59.95 + 
  3840x2160     60.00    60.00   
  2560x2880     59.98*   29.99   
  1920x1200     59.88   
  1920x1080     60.00   
  1680x1050     59.95   
  1600x1200     60.00   
  1280x1024     60.02   
  1280x800      59.81   
  1024x768      60.00   
  800x600       60.32   
  640x480       59.95    59.94   
DP-3 disconnected (normal left inverted right x axis y axis) 
       CscMatrix: 65536 0 0 0 0 65536 0 0 0 0 65536 0  
       BorderDimensions: 4  
               supported: 4 
       Border: 0 0 0 0  
               range: (0, 65535) 
       SignalFormat: TMDS  
               supported: TMDS 
       ConnectorType: DisplayPort  
       ConnectorNumber: 1  
       _ConnectorLocation: 1

       

       

       

      Attachments

        1. xorg.conf.txt
          2 kB
        2. xrandr.txt
          0.9 kB
        3. xrandr--listmonitors.txt
          0.1 kB
        4. xrandr--prop.txt
          5 kB

        Issue Links

          depends on

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          • Closed
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          • P2: Important - Urgent, should be fixed, but will not stop the release.
          • Closed
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          • P1: Critical - Urgent and Important, will STOP the release if matched with set FixVersion field. This includes regressions from the last version that are not edge cases; Data loss; Build issues; All but the most unlikely crashes/lockups/hanging; Serious usability issues and embarrassing bugs & Bugs critical to a deliverable. This is the highest possible priority for requirements.
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          • P1: Critical - Urgent and Important, will STOP the release if matched with set FixVersion field. This includes regressions from the last version that are not edge cases; Data loss; Build issues; All but the most unlikely crashes/lockups/hanging; Serious usability issues and embarrassing bugs & Bugs critical to a deliverable. This is the highest possible priority for requirements.
          • Closed
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