This is a quick implementation that avoids many
glyph cache lookups. We keep an array of direct
pointers in the text render node, and throw those
cached pointers away whenever any atlases have
been dropped (since that may invalidate the cached
glyphs).
We were putting big glyphs in the cache, in their
own texture, but forgetting to mark the texture
as permanent, so it could be reused, leading to
occasional misrendering. Fix this by marking these
textures as permanent, and explicitly freeing them
when the cache entry gets old.
Every few frames, we do extra work for the
cache aging. Arrange for the glyph and icon
caches to not cause extra work on the same
frame, to smooth things out.
There is no need for us to be very precise about
aging the glyph entries. It is enough to check
occasionally and mark old entries. This reduces
the overhead of work we do every frame on the
caches, at the cost of letting glyphs linger
a bit longer in the cache.
Make this function more similar to the icon
cache equivalent, and simplify it a bit. We
don't use the boolean return, and we don't need
to look at the age of entry when marking it
used.
Remember which atlases were removed, and only
check those when looking for icons or glyphs
to remove. For most frames, we don't have to
check at all since no atlases were removed.
We can just use memcmp here because even in the use of lookup keys with
C99 initializers, we can rely on any space between fields added by the
compiler to be zeroed. So we might as well use wider memory cmopares.
Pass the glyph position into the glyph caching functions,
not just the glyph index. This allows us to cache different
images for different subpixel positions.
We are currently using a weird mix of pango and cairo,
but there is no need for us to go through a pango
renderer here; we can just use cairo directly.
Use the same texture atlases to back both
the glyph and icon caches, and unify their
sizes and management. Store big glyphs
in separate textures, so all atlases have
the same size. Tweak some of the eviction
parameters.
We share the caches across all GL contexts
on a display, unless the GSK_NO_SHARED_CACHES
env var is set.
The logic here seems faulty. We want to keep
a timestamp that tells us when the glyph was
last used, so always update the timestamp.
And whenever we use a glyph, it turns 'young'
again, so remove it from the old pixels
accounting.
The (MAX_AGE, MAX_AGE+CHECK_INTERVAL) interval
is only relevant to prevent us from turning
a cached glyph old more than once, and that
is already taken care of.
We blindly assume everywhere that a single glyph will definitely fit on
one atlas, but that's not always the case.
For now, don't crash or produce GL errors.
This adds debug groups in various places, including the debug
nodes if those are in use. This makes the traces in tools like
renderdoc much easier to read.
The first set of glyphs is created with a timestamp of 1. Later we
subtract the glyph timestamp from the cache timestamp, meaning we end up
with numbers ending in 9, e.g. 59. Now unfortunately !(60 <= 59), so we
do not end up incrasing the old_pixels count of the cache. Later we then
call lookup() and DEcrease the old_pixels count, which makes the
unsigned int wrap and cause a huge old_pixels value, which causes us to
drop the cache.
