Three tightenings, all measured with the reloads now reported on stderr.
`set_math_channels()` treats an identical list as no change at all. It rebuilt
unconditionally, and a rebuild replaces the buffer and drops its history -- which a file
view then has to re-read from disk. The comparison is the graphs', and it leaves the nodes'
`x`/`y` out deliberately: those are the canvas's own, no op reads them, and a graph that
merely *moved* should not cost the buffer.
`reload_file_view()` fires only when the store is actually empty. A change that really
happened leaves it so in a file view (the rebuild replaces it, and there is no producer to
refill it); one that found nothing to do leaves it full, and reading a 200 MB file again for
that is the waste. `ScopeModel::stored_slots()` is the one-line accessor it needed.
Every reload now says so, because a second read of a file is worth accounting for:
[udpscope] reloaded <path> after a structural change: 402 samples back
Measured, `--open` a file:
session with no graphs 0 reloads
the math probe (3 real changes) 3 reloads, and all the readings stay equal
(`math x2 402 samples vs 402 time slots`)
I had offered this as "one extra read at `--open` startup", and that was wrong: with no
session there is no `apply_math_channels()` call at all, so there was never an extra read
to remove. What the tightenings buy is that a no-op application is now free, and that a
reload cannot happen unless the buffer was really lost. Each *genuine* change still costs
one re-read -- a rebuild drops the history by design, and preserving it across a rebuild is
a model change rather than this one.
Martino Ferrari
47d49e75ff