[Paint Preview] Add basic subsetting support

This CL adds basic subsetting support for paint previews. This depends
on Harfbuzz's subsetter and is based on the implementation in
SkPDFSubsetFont.

Part of landing:
https://chromium-review.googlesource.com/c/chromium/src/+/1786583

Bug: 1006242
Change-Id: I757543ab9a575dc829a6f2b7fc1bb9b89fef5c97
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1816730Reviewed-by: Dominik Röttsches <drott@chromium.org>
Reviewed-by: Ian Vollick <vollick@chromium.org>
Commit-Queue: Calder Kitagawa <ckitagawa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700264}

components/BUILD.gn

@@ -118,7 +118,6 @@ test("components_unittests") {
     "//components/omnibox/browser:unit_tests",
     "//components/open_from_clipboard:unit_tests",
     "//components/os_crypt:unit_tests",
-    "//components/paint_preview/common:unit_tests",
     "//components/password_manager/core/browser:unit_tests",
     "//components/password_manager/core/common:unit_tests",
     "//components/payments/core:unit_tests",
@@ -241,6 +240,7 @@ test("components_unittests") {
       "//components/page_image_annotation/core:unit_tests",
       "//components/page_load_metrics/browser:unit_tests",
       "//components/page_load_metrics/renderer:unit_tests",
+      "//components/paint_preview/common:unit_tests",
       "//components/password_manager/content/browser:unit_tests",
       "//components/payments/content:unit_tests",
       "//components/payments/content/utility:unit_tests",

components/paint_preview/DEPS

 include_rules = [
+  "+third_party/harfbuzz-ng/src/src",
   "+third_party/skia/include/core",
 ]

components/paint_preview/README.md

@@ -19,6 +19,9 @@ centralized to this directory. Parts of the code are consumed in;
 * `//content`
 * `//third_party/blink`
 
+NOTE: This feature depends on working with `//content` and `//third_party/blink`
+so it is incompatible with iOS.
+
 ## Directory Structure (WIP)
 
 * `common/` - Shared code; mojo, protos, and C++ code.

components/paint_preview/common/BUILD.gn

@@ -4,43 +4,50 @@
 
 import("//testing/test.gni")
 
-static_library("common") {
-  sources = [
-    "file_stream.cc",
-    "file_stream.h",
-    "glyph_usage.cc",
-    "glyph_usage.h",
-  ]
+if (!is_ios) {
+  static_library("common") {
+    sources = [
+      "file_stream.cc",
+      "file_stream.h",
+      "glyph_usage.cc",
+      "glyph_usage.h",
+      "subset_font.cc",
+      "subset_font.h",
+    ]
 
-  deps = [
-    "//base",
-    "//skia",
-  ]
-}
+    deps = [
+      "//base",
+      "//skia",
+      "//third_party:freetype_harfbuzz",
+    ]
+  }
 
-source_set("unit_tests") {
-  testonly = true
+  source_set("unit_tests") {
+    testonly = true
 
-  sources = [
-    "file_stream_unittest.cc",
-    "glyph_usage_unittest.cc",
-  ]
+    sources = [
+      "file_stream_unittest.cc",
+      "glyph_usage_unittest.cc",
+      "subset_font_unittest.cc",
+    ]
 
-  deps = [
-    ":common",
-    "//base",
-    "//base/test:test_support",
-    "//skia",
-    "//testing/gmock",
-    "//testing/gtest",
-  ]
-}
+    deps = [
+      ":common",
+      "//base",
+      "//base/test:test_support",
+      "//skia",
+      "//testing/gmock",
+      "//testing/gtest",
+      "//third_party:freetype_harfbuzz",
+    ]
+  }
 
-test("paint_preview_common_unit_tests") {
-  deps = [
-    ":unit_tests",
-    "//base",
-    "//base/test:test_support",
-    "//components/test:run_all_unittests",
-  ]
+  test("paint_preview_common_unit_tests") {
+    deps = [
+      ":unit_tests",
+      "//base",
+      "//base/test:test_support",
+      "//components/test:run_all_unittests",
+    ]
+  }
 }

components/paint_preview/common/subset_font.cc

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/paint_preview/common/subset_font.h"
+
+#include <memory>
+#include <utility>
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/macros.h"
+#include "third_party/harfbuzz-ng/src/src/hb-subset.h"
+#include "third_party/harfbuzz-ng/src/src/hb.h"
+#include "third_party/skia/include/core/SkStream.h"
+#include "third_party/skia/include/core/SkTypeface.h"
+
+namespace paint_preview {
+
+namespace {
+
+// Handles auto-deletion of harfbuzz objects.
+template <typename T, T* P>
+struct HbDeleter {
+  template <typename... Args>
+  auto operator()(Args&&... args) const
+      -> decltype(P(std::forward<Args>(args)...)) {
+    return P(std::forward<Args>(args)...);
+  }
+};
+
+using HbBlob =
+    std::unique_ptr<hb_blob_t,
+                    HbDeleter<decltype(hb_blob_destroy), &hb_blob_destroy>>;
+using HbFace =
+    std::unique_ptr<hb_face_t,
+                    HbDeleter<decltype(hb_face_destroy), &hb_face_destroy>>;
+using HbSubsetInput = std::unique_ptr<
+    hb_subset_input_t,
+    HbDeleter<decltype(hb_subset_input_destroy), &hb_subset_input_destroy>>;
+
+// Converts and SkStream to an SkData object without copy if possible or
+// falls back to a copy.
+sk_sp<SkData> StreamToData(std::unique_ptr<SkStreamAsset> stream) {
+  DCHECK(stream);
+  bool rewind = stream->rewind();
+  DCHECK(rewind);
+  DCHECK(stream->hasLength());
+  size_t size = stream->getLength();
+  // TODO: Replace with const SkData* = SkStreamAsset::getData() when Skia
+  // adds such a method.
+  if (const void* base = stream->getMemoryBase()) {
+    SkData::ReleaseProc proc = [](const void*, void* ctx) {
+      delete static_cast<SkStreamAsset*>(ctx);
+    };
+    return SkData::MakeWithProc(base, size, proc, stream.release());
+  }
+  return SkData::MakeFromStream(stream.get(), size);
+}
+
+// Converts SkData to a hb_blob_t.
+HbBlob MakeBlob(sk_sp<SkData> data) {
+  if (!data ||
+      !base::IsValueInRangeForNumericType<unsigned int, size_t>(data->size()))
+    return nullptr;
+  return HbBlob(hb_blob_create(static_cast<const char*>(data->data()),
+                               static_cast<unsigned int>(data->size()),
+                               HB_MEMORY_MODE_READONLY, nullptr, nullptr));
+}
+
+// Adds |glyph_id| to the set of glyphs to be retained.
+void AddGlyphs(hb_set_t* glyph_id_set, uint16_t glyph_id) {
+  hb_set_add(glyph_id_set, glyph_id);
+}
+
+}  // namespace
+
+// Implementation based on SkPDFSubsetFont() using harfbuzz.
+sk_sp<SkData> SubsetFont(SkTypeface* typeface, const GlyphUsage& usage) {
+  int ttc_index = 0;
+  sk_sp<SkData> data = StreamToData(typeface->openStream(&ttc_index));
+  HbFace face(hb_face_create(MakeBlob(data).get(), ttc_index));
+  HbSubsetInput input(hb_subset_input_create_or_fail());
+  if (!face || !input)
+    return nullptr;
+
+  hb_set_t* glyphs =
+      hb_subset_input_glyph_set(input.get());  // Owned by |input|.
+  usage.ForEach(base::BindRepeating(&AddGlyphs, base::Unretained(glyphs)));
+  hb_subset_input_set_retain_gids(input.get(), true);
+  hb_subset_input_set_drop_hints(input.get(), true);
+
+  HbFace subset_face(hb_subset(face.get(), input.get()));
+  HbBlob subset_blob(hb_face_reference_blob(subset_face.get()));
+  if (!subset_blob)
+    return nullptr;
+
+  unsigned int length = 0;
+  const char* subset_data = hb_blob_get_data(subset_blob.get(), &length);
+  if (!subset_data || !length)
+    return nullptr;
+
+  auto sk_data = SkData::MakeWithProc(
+      subset_data, static_cast<size_t>(length),
+      [](const void*, void* ctx) { hb_blob_destroy((hb_blob_t*)ctx); },
+      subset_blob.release());
+  if (!sk_data)
+    return nullptr;
+
+  // Ensure the data is in SkTypeface format so it will deserialize when
+  // embedded in an SkPicture. This is *not* a validation/sanitation and the
+  // inner workings may vary by platform.
+  auto sk_subset_typeface = SkTypeface::MakeFromData(sk_data);
+  if (!sk_subset_typeface)
+    return nullptr;
+  return sk_subset_typeface->serialize(
+      SkTypeface::SerializeBehavior::kDoIncludeData);
+}
+
+}  // namespace paint_preview

components/paint_preview/common/subset_font.h

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_PAINT_PREVIEW_COMMON_SUBSET_FONT_H_
+#define COMPONENTS_PAINT_PREVIEW_COMMON_SUBSET_FONT_H_
+
+#include "components/paint_preview/common/glyph_usage.h"
+#include "third_party/skia/include/core/SkData.h"
+#include "third_party/skia/include/core/SkRefCnt.h"
+
+class SkTypeface;
+
+namespace paint_preview {
+
+// Subsets |typeface| to only contain the glyphs in |usage|. Returns nullptr on
+// failure.
+sk_sp<SkData> SubsetFont(SkTypeface* typeface, const GlyphUsage& usage);
+
+}  // namespace paint_preview
+
+#endif  // COMPONENTS_PAINT_PREVIEW_COMMON_SUBSET_FONT_H_

components/paint_preview/common/subset_font_unittest.cc

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/paint_preview/common/subset_font.h"
+
+#include "components/paint_preview/common/glyph_usage.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/skia/include/core/SkData.h"
+#include "third_party/skia/include/core/SkRefCnt.h"
+#include "third_party/skia/include/core/SkStream.h"
+#include "third_party/skia/include/core/SkTypeface.h"
+
+namespace paint_preview {
+
+TEST(PaintPreviewSubsetFontTest, TestBasicSubset) {
+  auto typeface = SkTypeface::MakeDefault();
+  ASSERT_NE(typeface, nullptr);
+  SparseGlyphUsage sparse(typeface->countGlyphs());
+  sparse.Set(0);
+  uint16_t glyph_a = typeface->unicharToGlyph('a');
+  sparse.Set(glyph_a);
+  uint16_t glyph_t = typeface->unicharToGlyph('t');
+  sparse.Set(glyph_t);
+  auto subset_data = SubsetFont(typeface.get(), sparse);
+  ASSERT_NE(subset_data, nullptr);
+  SkMemoryStream stream(subset_data);
+  auto subset_typeface = SkTypeface::MakeDeserialize(&stream);
+  ASSERT_NE(subset_typeface, nullptr);
+
+  // Subsetting doesn't guarantee all glyphs are removed, so just check that the
+  // size is smaller and that the requested glyphs still exist and have the same
+  // glyphs ids.
+  auto origin_data =
+      typeface->serialize(SkTypeface::SerializeBehavior::kDoIncludeData);
+  EXPECT_LE(subset_data->size(), origin_data->size());
+  EXPECT_LE(subset_typeface->countTables(), typeface->countTables());
+  EXPECT_LE(subset_typeface->countGlyphs(), typeface->countGlyphs());
+
+  // TODO(ckitagawa): Find a reliable way to check that |glyph_{a, t}| are in
+  // the subset_typeface. This is non-trivial.
+}
+
+}  // namespace paint_preview