Extract the Skia implementation of HarfBuzz font to its own file

ui/gfx/harfbuzz_font_skia.cc

+// Copyright 2015 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 "ui/gfx/harfbuzz_font_skia.h"
+
+#include <limits>
+#include <map>
+
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "third_party/skia/include/core/SkPaint.h"
+#include "third_party/skia/include/core/SkTypeface.h"
+#include "ui/gfx/render_text.h"
+
+// Font data provider for HarfBuzz using Skia. Copied from Blink.

[msw, 2015/02/03 20:50:32]

nit: keep this comment with the FontData struct.

[ckocagil, 2015/02/05 04:56:44]

Done.

+// TODO(ckocagil): Eliminate the duplication. http://crbug.com/368375
+
+namespace gfx {
+
+namespace {
+
+class HarfBuzzFace;
+
+// Maps from code points to glyph indices in a font.
+typedef std::map<uint32_t, uint16_t> GlyphCache;
+
+typedef std::pair<HarfBuzzFace, GlyphCache> FaceCache;
+
+// TODO(ckocagil): This shouldn't grow indefinitely. Maybe use base::MRUCache?
+static std::map<SkFontID, FaceCache> g_face_caches;

[msw, 2015/02/03 20:50:32]

Can this remain a static member of CreateHarfBuzzFont?

[ckocagil, 2015/02/05 04:56:44]

Done.

+
+struct FontData {
+  FontData(GlyphCache* glyph_cache) : glyph_cache_(glyph_cache) {}
+
+  SkPaint paint_;
+  GlyphCache* glyph_cache_;
+};
+
+// Deletes the object at the given pointer after casting it to the given type.
+template<typename Type>
+void DeleteByType(void* data) {
+  Type* typed_data = reinterpret_cast<Type*>(data);
+  delete typed_data;
+}
+
+template<typename Type>
+void DeleteArrayByType(void* data) {
+  Type* typed_data = reinterpret_cast<Type*>(data);
+  delete[] typed_data;
+}
+
+// Outputs the |width| and |extents| of the glyph with index |codepoint| in
+// |paint|'s font.
+void GetGlyphWidthAndExtents(SkPaint* paint,
+                             hb_codepoint_t codepoint,
+                             hb_position_t* width,
+                             hb_glyph_extents_t* extents) {
+  DCHECK_LE(codepoint, std::numeric_limits<uint16_t>::max());
+  paint->setTextEncoding(SkPaint::kGlyphID_TextEncoding);
+
+  SkScalar sk_width;
+  SkRect sk_bounds;
+  uint16_t glyph = static_cast<uint16_t>(codepoint);
+
+  paint->getTextWidths(&glyph, sizeof(glyph), &sk_width, &sk_bounds);
+  if (width)
+    *width = SkScalarToFixed(sk_width);
+  if (extents) {
+    // Invert y-axis because Skia is y-grows-down but we set up HarfBuzz to be
+    // y-grows-up.
+    extents->x_bearing = SkScalarToFixed(sk_bounds.fLeft);
+    extents->y_bearing = SkScalarToFixed(-sk_bounds.fTop);
+    extents->width = SkScalarToFixed(sk_bounds.width());
+    extents->height = SkScalarToFixed(-sk_bounds.height());
+  }
+}
+
+// Writes the |glyph| index for the given |unicode| code point. Returns whether
+// the glyph exists, i.e. it is not a missing glyph.
+hb_bool_t GetGlyph(hb_font_t* font,
+                   void* data,
+                   hb_codepoint_t unicode,
+                   hb_codepoint_t variation_selector,
+                   hb_codepoint_t* glyph,
+                   void* user_data) {
+  FontData* font_data = reinterpret_cast<FontData*>(data);
+  GlyphCache* cache = font_data->glyph_cache_;
+
+  bool exists = cache->count(unicode) != 0;
+  if (!exists) {
+    SkPaint* paint = &font_data->paint_;
+    paint->setTextEncoding(SkPaint::kUTF32_TextEncoding);
+    paint->textToGlyphs(&unicode, sizeof(hb_codepoint_t), &(*cache)[unicode]);
+  }
+  *glyph = (*cache)[unicode];
+  return !!*glyph;
+}
+
+// Returns the horizontal advance value of the |glyph|.
+hb_position_t GetGlyphHorizontalAdvance(hb_font_t* font,
+                                        void* data,
+                                        hb_codepoint_t glyph,
+                                        void* user_data) {
+  FontData* font_data = reinterpret_cast<FontData*>(data);
+  hb_position_t advance = 0;
+
+  GetGlyphWidthAndExtents(&font_data->paint_, glyph, &advance, 0);
+  return advance;
+}
+
+hb_bool_t GetGlyphHorizontalOrigin(hb_font_t* font,
+                                   void* data,
+                                   hb_codepoint_t glyph,
+                                   hb_position_t* x,
+                                   hb_position_t* y,
+                                   void* user_data) {
+  // Just return true, like the HarfBuzz-FreeType implementation.
+  return true;
+}
+
+hb_position_t GetGlyphKerning(FontData* font_data,
+                              hb_codepoint_t first_glyph,
+                              hb_codepoint_t second_glyph) {
+  SkTypeface* typeface = font_data->paint_.getTypeface();
+  const uint16_t glyphs[2] = { static_cast<uint16_t>(first_glyph),
+                               static_cast<uint16_t>(second_glyph) };
+  int32_t kerning_adjustments[1] = { 0 };
+
+  if (!typeface->getKerningPairAdjustments(glyphs, 2, kerning_adjustments))
+    return 0;
+
+  SkScalar upm = SkIntToScalar(typeface->getUnitsPerEm());
+  SkScalar size = font_data->paint_.getTextSize();
+  return SkScalarToFixed(
+      SkScalarMulDiv(SkIntToScalar(kerning_adjustments[0]), size, upm));
+}
+
+hb_position_t GetGlyphHorizontalKerning(hb_font_t* font,
+                                        void* data,
+                                        hb_codepoint_t left_glyph,
+                                        hb_codepoint_t right_glyph,
+                                        void* user_data) {
+  FontData* font_data = reinterpret_cast<FontData*>(data);
+  if (font_data->paint_.isVerticalText()) {
+    // We don't support cross-stream kerning.
+    return 0;
+  }
+
+  return GetGlyphKerning(font_data, left_glyph, right_glyph);
+}
+
+hb_position_t GetGlyphVerticalKerning(hb_font_t* font,
+                                      void* data,
+                                      hb_codepoint_t top_glyph,
+                                      hb_codepoint_t bottom_glyph,
+                                      void* user_data) {
+  FontData* font_data = reinterpret_cast<FontData*>(data);
+  if (!font_data->paint_.isVerticalText()) {
+    // We don't support cross-stream kerning.
+    return 0;
+  }
+
+  return GetGlyphKerning(font_data, top_glyph, bottom_glyph);
+}
+
+// Writes the |extents| of |glyph|.
+hb_bool_t GetGlyphExtents(hb_font_t* font,
+                          void* data,
+                          hb_codepoint_t glyph,
+                          hb_glyph_extents_t* extents,
+                          void* user_data) {
+  FontData* font_data = reinterpret_cast<FontData*>(data);
+
+  GetGlyphWidthAndExtents(&font_data->paint_, glyph, 0, extents);
+  return true;
+}
+
+class FontFuncs {
+ public:
+  FontFuncs() : font_funcs_(hb_font_funcs_create()) {
+    hb_font_funcs_set_glyph_func(font_funcs_, GetGlyph, 0, 0);
+    hb_font_funcs_set_glyph_h_advance_func(
+        font_funcs_, GetGlyphHorizontalAdvance, 0, 0);
+    hb_font_funcs_set_glyph_h_kerning_func(
+        font_funcs_, GetGlyphHorizontalKerning, 0, 0);
+    hb_font_funcs_set_glyph_h_origin_func(
+        font_funcs_, GetGlyphHorizontalOrigin, 0, 0);
+    hb_font_funcs_set_glyph_v_kerning_func(
+        font_funcs_, GetGlyphVerticalKerning, 0, 0);
+    hb_font_funcs_set_glyph_extents_func(
+        font_funcs_, GetGlyphExtents, 0, 0);
+    hb_font_funcs_make_immutable(font_funcs_);
+  }
+
+  ~FontFuncs() {
+    hb_font_funcs_destroy(font_funcs_);
+  }
+
+  hb_font_funcs_t* get() { return font_funcs_; }
+
+ private:
+  hb_font_funcs_t* font_funcs_;
+
+  DISALLOW_COPY_AND_ASSIGN(FontFuncs);
+};
+
+base::LazyInstance<FontFuncs>::Leaky g_font_funcs = LAZY_INSTANCE_INITIALIZER;
+
+// Returns the raw data of the font table |tag|.
+hb_blob_t* GetFontTable(hb_face_t* face, hb_tag_t tag, void* user_data) {
+  SkTypeface* typeface = reinterpret_cast<SkTypeface*>(user_data);
+
+  const size_t table_size = typeface->getTableSize(tag);
+  if (!table_size)
+    return 0;
+
+  scoped_ptr<char[]> buffer(new char[table_size]);
+  if (!buffer)
+    return 0;
+  size_t actual_size = typeface->getTableData(tag, 0, table_size, buffer.get());
+  if (table_size != actual_size)
+    return 0;
+
+  char* buffer_raw = buffer.release();
+  return hb_blob_create(buffer_raw, table_size, HB_MEMORY_MODE_WRITABLE,
+                        buffer_raw, DeleteArrayByType<char>);
+}
+
+void UnrefSkTypeface(void* data) {
+  SkTypeface* skia_face = reinterpret_cast<SkTypeface*>(data);
+  SkSafeUnref(skia_face);
+}
+
+// Wrapper class for a HarfBuzz face created from a given Skia face.
+class HarfBuzzFace {
+ public:
+  HarfBuzzFace() : face_(NULL) {}
+
+  ~HarfBuzzFace() {
+    if (face_)
+      hb_face_destroy(face_);
+  }
+
+  void Init(SkTypeface* skia_face) {
+    SkSafeRef(skia_face);
+    face_ = hb_face_create_for_tables(GetFontTable, skia_face, UnrefSkTypeface);
+    DCHECK(face_);
+  }
+
+  hb_face_t* get() {
+    return face_;
+  }
+
+ private:
+  hb_face_t* face_;
+};
+
+}  // namespace
+
+// Creates a HarfBuzz font from the given Skia face and text size.
+hb_font_t* CreateHarfBuzzFont(SkTypeface* skia_face,
+                              SkScalar text_size,
+                              const FontRenderParams& params,
+                              bool background_is_transparent) {
+  FaceCache* face_cache = &g_face_caches[skia_face->uniqueID()];
+  if (face_cache->first.get() == NULL)
+    face_cache->first.Init(skia_face);
+
+  hb_font_t* harfbuzz_font = hb_font_create(face_cache->first.get());
+  const int scale = SkScalarToFixed(text_size);
+  hb_font_set_scale(harfbuzz_font, scale, scale);
+  FontData* hb_font_data = new FontData(&face_cache->second);
+  hb_font_data->paint_.setTypeface(skia_face);
+  hb_font_data->paint_.setTextSize(text_size);
+  // TODO(ckocagil): Do we need to update these params later?
+  internal::ApplyRenderParams(params, background_is_transparent,
+                              &hb_font_data->paint_);
+  hb_font_set_funcs(harfbuzz_font, g_font_funcs.Get().get(), hb_font_data,
+                    DeleteByType<FontData>);
+  hb_font_make_immutable(harfbuzz_font);
+  return harfbuzz_font;
+}
+
+}  // namespace gfx