Deduplicate typefaces across sub-pictures

Old flow to serialize a picture:
   1) serialize picture ops
   2) serialize all sub pictures recursively
   3) flatten the rest of this picture into a buffer, deduping flattenable factories and typefaces as we go
   4) serialize the factories and typefaces
   5) serialize the bytes from 3)

This allows the data in step 5) to refer to the deduplicated factories and typefaces from step 4).  But, each sub picture in step 2) is completely siloed, so they can't dedup with the parent picture or each other.

New flow:
   1) serialize picture ops
   2) flatten the rest of this picture into a buffer, deduping flattenable factories and typefaces as we go
   3) dummy-serialize sub pictures into /dev/null, with the effect of adding any new typefaces to our dedup set
   4) serialize the factories and typefaces
   5) serialize the bytes from 2)
   6) serialize all sub pictures recursively, with perfect deduplication because of step 3).

Now all typefaces in the top-level picture and all sub pictures recursively should end up deduplicated in the top-level typeface set.

Decoding changes are similar: we just thread through the top-level typefaces to the sub pictures.  What's convenient / surprising is that this new code correctly reads old pictures if we just have each picture prefer its local typeface set over the top-level one: old pictures always just use their own typefaces, and new pictures always use the top-level ones.

BUG=skia:4092

Review URL: https://codereview.chromium.org/1233953004

1 files changed, 15 insertions, 2 deletions

diff --git a/src/core/SkPicture.cpp b/src/core/SkPicture.cpp
index 02d495e4c6..26ec76184e 100644
--- a/src/core/SkPicture.cpp
+++ b/src/core/SkPicture.cpp
@@ -139,11 +139,18 @@ SkPicture* SkPicture::Forwardport(const SkPictInfo& info, const SkPictureData* d
 }
 
 SkPicture* SkPicture::CreateFromStream(SkStream* stream, InstallPixelRefProc proc) {
+    return CreateFromStream(stream, proc, nullptr);
+}
+
+SkPicture* SkPicture::CreateFromStream(SkStream* stream,
+                                       InstallPixelRefProc proc,
+                                       SkTypefacePlayback* typefaces) {
     SkPictInfo info;
     if (!InternalOnly_StreamIsSKP(stream, &info) || !stream->readBool()) {
         return nullptr;
     }
-    SkAutoTDelete<SkPictureData> data(SkPictureData::CreateFromStream(stream, info, proc));
+    SkAutoTDelete<SkPictureData> data(
+            SkPictureData::CreateFromStream(stream, info, proc, typefaces));
     return Forwardport(info, data);
 }
 
@@ -166,13 +173,19 @@ SkPictureData* SkPicture::backport() const {
 }
 
 void SkPicture::serialize(SkWStream* stream, SkPixelSerializer* pixelSerializer) const {
+    this->serialize(stream, pixelSerializer, nullptr);
+}
+
+void SkPicture::serialize(SkWStream* stream,
+                          SkPixelSerializer* pixelSerializer,
+                          SkRefCntSet* typefaceSet) const {
     SkPictInfo info = this->createHeader();
     SkAutoTDelete<SkPictureData> data(this->backport());
 
     stream->write(&info, sizeof(info));
     if (data) {
         stream->writeBool(true);
-        data->serialize(stream, pixelSerializer);
+        data->serialize(stream, pixelSerializer, typefaceSet);
     } else {
         stream->writeBool(false);
     }