Old heuristic was to find the first monitor that expressed a preference,
then attempt to get all other monitors to agree. This doesn't work
particularly well when the two sets of modes don't precisely intersect,
you get overlapping-but-not-identical output geometry and things go wrong.
New heuristic is:
- Exact user preference, if given
- Exact output preference, if the same for all outputs
- Best (largest) mode of modes common to all outputs:
- with the same aspect ratio as all outputs (may be NULL)
- with 4:3 aspect ratio
- Then the old heuristic to try to get something lit
Note that it is simply not doable to have a reliable initial output guess if
you insist on trying to clone all outputs together. It's far too easy to
end up with displays that simply don't have modes in common. We need to
switch to right-of placement someday, once we're not limited to CRTC size
limits and we have working multi-GPU in RANDR.
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