Enforce saveLayer ignoring restore paint's mask filter
Documentation specifies that only the alpha, color filter, image filter
and blend mode are used when restoring the saved layer. The coverage that
would be sent to the mask filter is ill-defined, whereas the explicit
boundary of the separate clip image gets around this.
This also removes the issue of the order in which the mask filter and
image filter would be applied.
Some GMs exercised the save layer with mask filter, but those have
been updated to either expect the MF to be ignored, or modified to
no longer use saveLayer+MF. While Android and Flutter expose a saveLayer
with general Paint API, their documentation matches SkCanvas so hopefully
no one is actually relying on the mask filter in those cases. It does
not appear as if Chrome ever tries to use a saveLayer+MF.
Bug: skia:9561
Change-Id: I67a350fbf565683ea60ea88f83a91270e7dcd187
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/274508
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
diff --git a/RELEASE_NOTES.txt b/RELEASE_NOTES.txt
index 7cc301b..3b2d7e1 100644
--- a/RELEASE_NOTES.txt
+++ b/RELEASE_NOTES.txt
@@ -45,6 +45,11 @@
* SkSurface::ReplaceBackendTexture takes ContentChangeMode as a parameter,
which allow callers to specify whether retain a copy of the current content.
+
+ * Enforce the existing documentation in SkCanvas::saveLayer that it ignores
+ any mask filter on the restore SkPaint. The 'coverage' of a layer is
+ ill-defined, and masking should be handled by pre-clipping or using the
+ auxiliary clip mask image of the SaveLayerRec.
* * *