[skottie] Fix text-on-path tracking
Tracking and line spacing computations require knowledge of cumulative
values for the whole line => we need two passes:
1) compute cumulative values
2) compute per-fragment position adjustments
Currently, #1 is implemented in the main onSync() loop (as we iterate
to compute fragment props) and #2 is post-applied via adjustLineProps(),
after the main loop.
The problem is adjustLineProps() is executed after positioning glyphs on
path, and tracking is not taken into account for path positioning
(instead it moves glyphs horizontally, unrelated to the path).
To fix this, we need tracking adjustments to be applied before
positioning on path (which is performed in fragmentMatrix()).
- move the cumulative tracking computation to a dedicate lambda
(compute_linewide_props)
- move the fragment position adjustments to the main onSync() loop
(that way they participate in path positioning)
- to avoid executing the first pass unnecessarily, add flags to detect
the presence of tracking and line spacing animators.
Change-Id: Ieef2afb53ffe14177eba0ef41dc5c71149cab070
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/518696
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@google.com>
5 files changed