Thank you for all the suggestions.
I made a list of them, but while pondering them something else occurred to me:
that, since the desktop manager seemed to be starting at the correct
resolution, the problem perhaps wasn't with X per se, but with some setting
for TDE that was confusing the issue.
So I renamed ~/.trinity and rebooted (yes, I know that the reboot probably
wasn't necessary, but I wanted to get a completely uncontaminated situation,
with both X and TDE starting with no chance of any leftover junk confusing
things).
TDE came up at 1920x1200.
So far, everything now seems to be working correctly. So I've tentatively
concluded that some leftover configuration parameter somewhere was causing TDE
to start at a resolution different from the X resolution, and that from now on
it should start at the correct resolution.
Somewhere I imagine that there's documentation for all the configuration
parameters that affect TDE startup, but I was unable to find said
documentation; so while I'm happy that things now seem to be working, I'm not
particularly comfortable with the solution. If someone knows where detailed
documentation for TDE configuration can be found, I'd be delighted if they
would share that information.
Indeed, the entire TDE startup process, really: somewhere there's presumably
something that tells X to start sddm when X starts; and somewhere else there
must be something that tells TDE to start when "TDE" is selected and I provide
login credentials to sddm; and then TDE must start... but the details of any
of this seem to be hard to find. I'd really like to educate myself to
understand every step in the process.
Doc
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Web: http://enginehousebooks.com/drevans
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