зеркало из https://github.com/mozilla/gecko-dev.git
9c4535798f
This replaces our DrawTargetCapture hack with a similar but more powerful TextDrawTarget
hack. The old design had several limitations:
* It couldn't handle shadows
* It couldn't handle selections
* It couldn't handle font/color changes in a single text-run
* It couldn't handle decorations (underline, overline, line-through)
Mostly this was a consequence of the fact that it only modified the start and end
of the rendering algorithm, and therefore couldn't distinguish draw calls for different
parts of the text.
This new design is based on a similar principle as DrawTargetCapture, but also passes
down the TextDrawTarget in the drawing arguments, so that the drawing algorithm can
notify us of changes in phase (e.g. "now we're doing underlines"). This also lets us
directly pass data to TextDrawTarget when possible (as is done for shadows and selections).
In doing this, I also improved the logic copied from ContainsOnlyColoredGlyphs to handle
changes in font/color mid-text-run (which can happen because of font fallback).
The end result is:
* We handle all shadows natively
* We handle all selections natively
* We handle all decorations natively
* We handle font/color changes in a single text-run
* Although we still hackily intercept draw calls
* But we don't need to buffer commands, reducing total memcopies
In addition, this change integrates webrender's PushTextShadow and PushLine APIs,
which were designed for this use case. This is only done in the layerless path;
WebrenderTextLayer continues to be semantically limited, as we aren't actively
maintaining non-layers-free webrender anymore.
This also doesn't modify TextLayers, to minimize churn. In theory they can be
augmented to support the richer semantics that TextDrawTarget has, but there's
little motivation since the API is largely unused with this change.
MozReview-Commit-ID: 4IjTsSW335h
--HG--
extra : rebase_source : d69f69648ade5c7a8e6bb756f4b8ab9e2543e576
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