Currently, we treat track matte source layers (tagged with td:1) as single-shot mask triggers:
we apply once to the following layer, then move on.
But track mattes can cascade: a layer with a matte can itself be applied as a track matte for the
following layer.
Also, for matte/masking purposes, only the layer content is being considered (ignoring blend mode
and any masks applied to the matte itself).
To support this, refactor the layer attachment code:
- instead of tracking the presence of a single-shot matte source, always track
previous layer content trees
- instead of triggering matte attachment in the presence of a matte source, trigger based on
the matte *target* property (tt: X)
- log errors on unknown matte modes
Change-Id: I6c71d4007e1e27d3f3a139344bbf367d7bc6e29d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/259820
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
