The user can now replay *all* earlier selection operations until the next
session undo/redo command, or the completion of a new operation.
Nothing relating to selection ops is stored, and selection operation history
is begun on first idle.
Selection operation history is fundamentally different from the history of
operations which act on a selection in terms of both their viewport and the
amount of information required to replay them.
WRT undo, the user of a selection op doesn't care about the viewport state
at the beginning of an op, but rather that at the end of the previous one.
This shows that PBD::Timer is pretty much identical in terms of timing and CPU
usage as Glib TimeoutSources.
They also show the differences on Windows when setting the minimum Multimedia Timer
resolution using timeBeginPeriod
We're still a very long way from tolerant of weird SMF files (libsmf takes a
"crash if input is not exactly perfect" philosophy, if we're going to be polite
and elevate such a thing to "philosophy"), but at least we'll get what's there
from files truncated by old broken versions of Ardour or other situations.
... almost. There are some artifacts when you zoom out while recording that I
can't figure out, but whatever.
Also fix performance issues caused by last attempt at rec display while zoom.
I can't figure out why a change has a NULL note; that shouldn't happen, but it
does. Worse case scenario is some undo loss, so better to print something
informative and soldier on than crash. Hopefully this will help track down the
real cause with more testing.
Much like everything else in midnam, it's not specified whether the numbers are
0 or 1 relative, but everything out there seems to be 0 relative and this
matches the canvas, so go with that.
