a5bbf0b769 introduced text-run
shaping.
Do avoid having to re-shape non-changing strings every time the bar is
refreshed, the *particle* (i.e. not the exposable) caches the last
shaped text-run.
Then, in expose(), it then assumes that that cached text-run is
the *same* text-run as returned from begin_expose().
This is true in most cases, but *not* when a single particle is
re-used to instantiate multiple exposables, as is commonly done by
modules generating dynlists. For example, the i3/sway module.
This fixes it, by making the cache growable, and by adding a “lock” to
each cache entry.
The lock is set in begin_expose(), to indicate that this particular
cache entry is needed in expose().
If we can’t find a matching cache entry, we first try to find a free
“slot” by searching for either unused, or used-but-not-locked cache
entries.
If that fails, we grow the cache and add a new entry.
In expose(), we unset the lock.
Closes#47
15ed0e043b