[ale] Epilogue: Raspian Screen Duplicating - How Hard Can It Be?
neal at mnopltd.com
neal at mnopltd.com
Fri Jan 19 13:53:00 EST 2024
A quick epilogue: Apparently the most recent Raspian image comes with
this WayLand graphical interface in place of the more traditional X.
And apparently Wayland breaks a whole lot of china,
There is an option in raspi-config to revert back to X, and at that
point xrandr stuff "just works".
On 2024-01-01 20:18, Neal Rhodes via Ale wrote:
> Thanks for the reply. Fair enough on resolution. Frankly, VGA
> resolution would be fine. We're putting up big words.
>
> I plugged in the 2nd monitor again after dinner, and the xrandr
> --current now reports the 2nd HDMI as XWAYLAND2, not XWAYLAND1.
>
> I tried your suggestion regarding using the Screen Layout Editor, and
> indeed one can position the 2nd HDMI on top of the 1st. Then what
> happens is IF you move a window on the first screen, it shows up on
> both. UNTIL you let go of the mouse button, when it disappears.
>
> I did get the xrandr --output XWAYLAND2 --same-as XWAYLAND0 to run to
> completion with out errors, and got the same behavior.
>
> Rebooted, and the 2nd HDMI was back to XWAYLAND1.
>
> neal at raspberrypi:~ $ xrandr --output XWAYLAND1 --same-as XWAYLAND0
> X Error of failed request: BadMatch (invalid parameter attributes)
> Major opcode of failed request: 139 (RANDR)
> Minor opcode of failed request: 7 (RRSetScreenSize)
> Serial number of failed request: 29
> Current serial number in output stream: 30
>
> This says to me that the syntax was ok, and it passed the initial
> edits, and tried to make that action.
>
> As you note, these are nearly identical displays. The only difference
> I spot is 0 has 510mm, and 1 has 520mm.
>
> I did find some pretty dense discussion of mirroring displays of
> different resolution:
> https://www.baeldung.com/linux/mirror-monitors-different-resolutions
> but it's waaaaaaay to late in the day to try and parse that, especially
> with light grey print on white.
>
> As you note, a splitter might be less of a headache than this, which i
> sure thought would be simple.
>
> On 2024-01-01 16:25, Alex Carver via Ale wrote:
> Answering in reverse, if your projector and TV will have different
> resolutions then nothing is going to save you short of just making the
> Pi display at the lowest resolution of the two devices.
>
> Simplest solution is an actual HDMI splitter and then you don't have to
> think about it.
>
> But you can run this to get the current displays:
> xrandr --current
>
> Some posts suggest you can use the graphical screen setup tool (Screen
> Layout Editor) to overlap the monitors which will result in sharing
> content. Drag one monitor over the top of the other.
>
> On 2024-01-01 12:48, Neal Rhodes via Ale wrote:
>
> Trying to stay retired, but a fella can't never get totally away from
> the sea....
>
> Needing to setup a PI 4B to simply display words for an Irish Pub Night
> to both the onboard HDMI outputs. One will go to a projector; the
> other to a 40" TV. Both HDMI. Both need to stay in Sync.
>
> I'm testing it now on a pair of 1920x1080 HDMI monitors. Both work fine
> as independent monitors.
>
> My notes on how to do this came from Bing AI, courtesy of Raspian
> Forums, and seemed pretty simple:
>
> Y_es, you can make both HDMI outputs on a Raspberry Pi 4 have the same
> output on Raspbian. Here are the steps:_
> _ _
> _Use the xrandr command to mirror the displays1. Replace <projector>
> and <desktop> with your display names:_
> _xrandr --output <projector> --same-as <desktop>_
> _In the example provided in the forum, <projector> was HDMI-2, and
> <desktop> was HDMI-11._
> _To check the display names, run the following command when both
> displays are attached1:_
> _xrandr --current_
> _ _
> _Please note that these steps should work by default on Raspberry Pi
> OS, Bullseye2. If you encounter any issues, please let me know! I'm
> here to help._
>
> Alas, it ain't working.
>
> eal at raspberrypi:~ $ xrandr
> Screen 0: minimum 16 x 16, current 3840 x 1080, maximum 32767 x 32767
> XWAYLAND0 connected 1920x1080+0+0 (normal left inverted right x axis y
> axis) 510mm x 290mm
> 1920x1080 59.96*+
> 1440x1080 59.99
> 1400x1050 59.98
> 1280x1024 59.89
> 1280x960 59.94
> 1152x864 59.96
> 1024x768 59.92
> 800x600 59.86
> 640x480 59.38
> 320x240 59.52
> 1680x1050 59.95
> 1440x900 59.89
> 1280x800 59.81
> 720x480 59.71
> 640x400 59.95
> 320x200 58.96
> 1600x900 59.95
> 1368x768 59.88
> 1280x720 59.86
> 1024x576 59.90
> 864x486 59.92
> 720x400 59.55
> 640x350 59.77
> XWAYLAND1 connected 1920x1080+1920+0 (normal left inverted right x axis
> y axis) 520mm x 290mm
> 1920x1080 59.96*+
> 1440x1080 59.99
> 1400x1050 59.98
> 1280x1024 59.89
> 1280x960 59.94
> 1152x864 59.96
> 1024x768 59.92
> 800x600 59.86
> 640x480 59.38
> 320x240 59.52
> 1680x1050 59.95
> 1440x900 59.89
> 1280x800 59.81
> 720x480 59.71
> 640x400 59.95
> 320x200 58.96
> 1600x900 59.95
> 1368x768 59.88
> 1280x720 59.86
> 1024x576 59.90
> 864x486 59.92
> 720x400 59.55
> 640x350 59.77
> neal at raspberrypi:~ $ xrandr --listmonitors
> Monitors: 2
> 0: +XWAYLAND0 1920/510x1080/290+0+0 XWAYLAND0
> 1: +XWAYLAND1 1920/520x1080/290+1920+0 XWAYLAND1
> neal at raspberrypi:~ $ xrandr --output 1 --same-as 0
> warning: output 1 not found; ignoring
> neal at raspberrypi:~ $ Xrandr
> bash: Xrandr: command not found
> neal at raspberrypi:~ $ xrandr --output XWAYLAND1 --same-as XWAYLAND0
> X Error of failed request: BadMatch (invalid parameter attributes)
> Major opcode of failed request: 139 (RANDR)
> Minor opcode of failed request: 7 (RRSetScreenSize)
> Serial number of failed request: 29
> Current serial number in output stream: 30
> neal at raspberrypi:~ $ xrandr --output +XWAYLAND1 --same-as +XWAYLAND0
> warning: output +XWAYLAND1 not found; ignoring
>
> The Screen Layout Editor shows displays as HDMI-A-1 and HDMI-A-2, so I
> also tried...
>
> neal at raspberrypi:~ $ xrandr --output HDMI-A-2 --same-as HDMI-A-1
> warning: output HDMI-A-2 not found; ignoring
> neal at raspberrypi:~ $ xrandr --output HDMI-2 --same-as HDMI-1
> warning: output HDMI-2 not found; ignoring
>
> I don't see an option in xrandr to simply tell me what outputs it
> thinks it has.
>
> And, is there a better way of doing this? Also considering that the
> real use will involve beer, and the projector may have different
> resolution from the TV?
>
> regards,
>
> Neal
>
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