Currently the SkStrikeClient is designed to pull fonts from the server
on demand, and to pre-fetch a batched request by analyzing the ops using
a SkTextBlobCacheDiffCanvas. This change modifies the design to support
a push based model, where the server pushes fonts required by the client
and sets up the requisite SkGlyphCaches on the client prior to
rasterizing the ops.
This model still relies on the SkTextBlobCacheDiffCanvas for analyzing
the glyphs required for rasterizing an op. The glyph caches required for
raster are locked and missing glyphs to be sent to the client are tracked
by the SkStrikeServer. The embedder can serialize this font data at any
point, but must ensure that this data is deserialized by the
SkStrikeClient at the remote end, before rasterizing any ops analyzed
prior to serialization. Any refs on the caches are released once the
font data is serialized by the server.
The locking of glyph caches relies on the embedder providing discardable
handles. These handles can be created on the server and serialized to be
sent to the client, and map to an instance of SkGlyphCache. This allows
the server to control the lifetime of the caches on the client.
Bug: skia:7515
Change-Id: Id39f346b47b60899778404bbd0429ee811d0e53b
Reviewed-on: https://skia-review.googlesource.com/120283
Commit-Queue: Khusal Sagar <khushalsagar@chromium.org>
Reviewed-by: Herb Derby <herb@google.com>
101d56359a