xserver and splitting ultra-wide monitors

Keith Packard keithp at keithp.com
Thu Sep 29 20:41:22 UTC 2022


Michael Wyraz <michael at wyraz.de> writes:

> For the second monitor, the output must be set to "none" which is 
> obviously wrong since it is connected to a device. The reason why it is 
> set to "none" is some code in xserver that removes an monitor if another 
> one is added to the same output:

That's actually required in the RandR spec:

	For each output in 'info.outputs, each one is removed from all
	pre-existing Monitors. If removing the output causes the list of
	outputs for that Monitor to become empty, then that Monitor will
	be deleted as if RRDeleteMonitor were called.

The notion of splitting one physical output into multiple virtual
monitors was not considered when this extension was defined, which is
why it doesn't work. I don't see any particular reason for *not*
supporting your use case.

However, there are subtleties here. We want to remove any automatically
created 'Monitor' objects when mapping user-specified monitors to
them, and we want to re-generate automatically generated 'Monitors' when
all virtual monitors associated with an output are removed.

I think what we want is:

 * If no user-specified Monitors map to a particular Output, then automatically
   create a Monitor for that Output

 * If any user-specified Monitors map to a particular Output, then
   remove the automatically generated Monitor for that Output.
   
In the current spec, there's no real separation between user-specified
and automatically-generated Monitors, I think that would be necessary to
make this work?

-- 
-keith
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