Rebase the libtxt integration by @GaryQian onto the current engine head (#4022)

See https://github.com/flutter/engine/pull/3964

BUILD.gn

@@ -9,6 +9,7 @@ group("flutter") {
     "//flutter/lib/snapshot:flutter_patched_sdk",
     "//flutter/lib/snapshot:generate_snapshot_bin",
     "//flutter/sky",
+    "//flutter/third_party/txt",
   ]
 
   if (!is_fuchsia) {

common/settings.h

@@ -27,6 +27,7 @@ struct Settings {
   bool use_test_fonts = false;
   bool dart_non_checked_mode = false;
   bool enable_software_rendering = false;
+  bool using_blink = true;
   std::string aot_snapshot_path;
   std::string aot_vm_snapshot_data_filename;
   std::string aot_vm_snapshot_instr_filename;

lib/ui/BUILD.gn

@@ -54,10 +54,18 @@ source_set("ui") {
     "semantics/semantics_update.h",
     "semantics/semantics_update_builder.cc",
     "semantics/semantics_update_builder.h",
+    "text/font_collection_mgr.cc",
+    "text/font_collection_mgr.h",
     "text/paragraph.cc",
     "text/paragraph.h",
     "text/paragraph_builder.cc",
     "text/paragraph_builder.h",
+    "text/paragraph_impl.cc",
+    "text/paragraph_impl.h",
+    "text/paragraph_impl_blink.cc",
+    "text/paragraph_impl_blink.h",
+    "text/paragraph_impl_txt.cc",
+    "text/paragraph_impl_txt.h",
     "text/text_box.cc",
     "text/text_box.h",
     "ui_dart_state.cc",
@@ -83,6 +91,7 @@ source_set("ui") {
     "//flutter/flow",
     "//flutter/glue",
     "//flutter/sky/engine",
+    "//flutter/third_party/txt",
     "//lib/tonic",
     "//third_party/skia",
     "//third_party/skia:gpu",

lib/ui/text/font_collection_mgr.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.
+
+// This class creates and holds the txt::FontCollection that contains the
+// Default and Custom fonts.
+
+#include "flutter/lib/ui/text/font_collection_mgr.h"
+
+#include "lib/tonic/converter/dart_converter.h"
+#include "lib/tonic/dart_args.h"
+#include "lib/tonic/dart_binding_macros.h"
+#include "lib/tonic/dart_library_natives.h"
+
+using tonic::ToDart;
+
+namespace blink {
+
+IMPLEMENT_WRAPPERTYPEINFO(ui, FontCollectionMgr);
+
+#define FOR_EACH_BINDING(V)                            \
+  V(FontCollectionMgr, initializeFontCollection)       \
+  V(FontCollectionMgr, initializeFontCollectionSingle) \
+  V(FontCollectionMgr, initializeFontCollectionMultiple)
+
+DART_BIND_ALL(FontCollectionMgr, FOR_EACH_BINDING)
+
+txt::FontCollection* FontCollectionMgr::kFontCollection = nullptr;
+
+void FontCollectionMgr::addFontDir(std::string font_dir) {
+  if (kFontCollection == nullptr)
+    initializeFontCollection();
+  kFontCollection->AddFontMgr(font_dir);
+}
+
+void FontCollectionMgr::initializeFontCollection() {
+  txt::FontCollection font_collection = txt::FontCollection();
+  kFontCollection = &font_collection;
+}
+
+void FontCollectionMgr::initializeFontCollectionSingle(std::string font_dir) {
+  txt::FontCollection font_collection = txt::FontCollection(font_dir);
+  kFontCollection = &font_collection;
+}
+
+void FontCollectionMgr::initializeFontCollectionMultiple(
+    std::vector<std::string> font_dirs) {
+  txt::FontCollection font_collection = txt::FontCollection(font_dirs);
+  kFontCollection = &font_collection;
+}
+
+}  // namespace blink

lib/ui/text/font_collection_mgr.h

+// 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.
+
+// This class creates and holds the txt::FontCollection that contains the
+// Default and Custom fonts.
+
+#ifndef FLUTTER_LIB_UI_TEXT_FONT_COLLECTION_MGR_H_
+#define FLUTTER_LIB_UI_TEXT_FONT_COLLECTION_MGR_H_
+
+
+#include "flutter/sky/engine/wtf/PassOwnPtr.h"
+#include "flutter/third_party/txt/src/txt/font_collection.h"
+#include "lib/tonic/dart_wrappable.h"
+
+namespace tonic {
+class DartLibraryNatives;
+}  // namespace tonic
+
+namespace blink {
+
+class FontCollectionMgr : public ftl::RefCountedThreadSafe<FontCollectionMgr>,
+                          public tonic::DartWrappable {
+  DEFINE_WRAPPERTYPEINFO();
+  FRIEND_MAKE_REF_COUNTED(FontCollectionMgr);
+
+ public:
+  static txt::FontCollection* kFontCollection;
+
+  static void addFontDir(std::string font_dir);
+
+  static void initializeFontCollection();
+
+  static void initializeFontCollectionSingle(std::string font_dir);
+
+  static void initializeFontCollectionMultiple(
+      std::vector<std::string> font_dirs);
+
+  static void RegisterNatives(tonic::DartLibraryNatives* natives);
+};
+
+}  // namespace blink
+
+#endif  // FLUTTER_LIB_UI_TEXT_FONT_COLLECTION_MGR_H_

lib/ui/text/paragraph.cc

@@ -4,14 +4,17 @@
 
 #include "flutter/lib/ui/text/paragraph.h"
 
+#include "flutter/common/settings.h"
 #include "flutter/common/threads.h"
 #include "flutter/sky/engine/core/rendering/PaintInfo.h"
-#include "flutter/sky/engine/core/rendering/RenderText.h"
 #include "flutter/sky/engine/core/rendering/RenderParagraph.h"
+#include "flutter/sky/engine/core/rendering/RenderText.h"
 #include "flutter/sky/engine/core/rendering/style/RenderStyle.h"
 #include "flutter/sky/engine/platform/fonts/FontCache.h"
 #include "flutter/sky/engine/platform/graphics/GraphicsContext.h"
 #include "flutter/sky/engine/platform/text/TextBoundaries.h"
+#include "flutter/sky/engine/wtf/PassOwnPtr.h"
+#include "lib/ftl/logging.h"
 #include "lib/ftl/tasks/task_runner.h"
 #include "lib/tonic/converter/dart_converter.h"
 #include "lib/tonic/dart_args.h"
@@ -41,13 +44,16 @@ IMPLEMENT_WRAPPERTYPEINFO(ui, Paragraph);
 DART_BIND_ALL(Paragraph, FOR_EACH_BINDING)
 
 Paragraph::Paragraph(PassOwnPtr<RenderView> renderView)
-    : m_renderView(renderView) {}
+    : m_paragraphImpl(std::make_unique<ParagraphImplBlink>(renderView)) {}
+
+Paragraph::Paragraph(std::unique_ptr<txt::Paragraph> paragraph)
+    : m_paragraphImpl(
+          std::make_unique<ParagraphImplTxt>(std::move(paragraph))) {}
 
 Paragraph::~Paragraph() {
   if (m_renderView) {
     RenderView* renderView = m_renderView.leakPtr();
-    Threads::UI()->PostTask(
-        [renderView]() { renderView->destroy(); });
+    Threads::UI()->PostTask([renderView]() { renderView->destroy(); });
   }
 }
 
@@ -59,144 +65,51 @@ size_t Paragraph::GetAllocationSize() {
 }
 
 double Paragraph::width() {
-  return firstChildBox()->width();
+  return m_paragraphImpl->width();
 }
 
 double Paragraph::height() {
-  return firstChildBox()->height();
+  return m_paragraphImpl->height();
 }
 
 double Paragraph::minIntrinsicWidth() {
-  return firstChildBox()->minPreferredLogicalWidth();
+  return m_paragraphImpl->minIntrinsicWidth();
 }
 
 double Paragraph::maxIntrinsicWidth() {
-  return firstChildBox()->maxPreferredLogicalWidth();
+  return m_paragraphImpl->maxIntrinsicWidth();
 }
 
 double Paragraph::alphabeticBaseline() {
-  return firstChildBox()->firstLineBoxBaseline(
-      FontBaselineOrAuto(AlphabeticBaseline));
+  return m_paragraphImpl->alphabeticBaseline();
 }
 
 double Paragraph::ideographicBaseline() {
-  return firstChildBox()->firstLineBoxBaseline(
-      FontBaselineOrAuto(IdeographicBaseline));
+  return m_paragraphImpl->ideographicBaseline();
 }
 
 bool Paragraph::didExceedMaxLines() {
-  RenderBox* box = firstChildBox();
-  ASSERT(box->isRenderParagraph());
-  RenderParagraph* paragraph = static_cast<RenderParagraph*>(box);
-  return paragraph->didExceedMaxLines();
+  return m_paragraphImpl->didExceedMaxLines();
 }
 
 void Paragraph::layout(double width) {
-  FontCachePurgePreventer fontCachePurgePreventer;
-
-  int maxWidth = LayoutUnit(width);  // Handles infinity properly.
-  m_renderView->setFrameViewSize(IntSize(maxWidth, intMaxForLayoutUnit));
-  m_renderView->layout();
+  m_paragraphImpl->layout(width);
 }
 
 void Paragraph::paint(Canvas* canvas, double x, double y) {
-  SkCanvas* skCanvas = canvas->canvas();
-  if (!skCanvas)
-    return;
-
-  FontCachePurgePreventer fontCachePurgePreventer;
-
-  // Very simplified painting to allow painting an arbitrary (layer-less)
-  // subtree.
-  RenderBox* box = firstChildBox();
-  skCanvas->translate(x, y);
-
-  GraphicsContext context(skCanvas);
-  Vector<RenderBox*> layers;
-  LayoutRect bounds = box->absoluteBoundingBoxRect();
-  FTL_DCHECK(bounds.x() == 0 && bounds.y() == 0);
-  PaintInfo paintInfo(&context, enclosingIntRect(bounds), box);
-  box->paint(paintInfo, LayoutPoint(), layers);
-  // Note we're ignoring any layers encountered.
-  // TODO(abarth): Remove the concept of RenderLayers.
-
-  skCanvas->translate(-x, -y);
+  m_paragraphImpl->paint(canvas, x, y);
 }
 
 std::vector<TextBox> Paragraph::getRectsForRange(unsigned start, unsigned end) {
-  if (end <= start || start == end)
-    return std::vector<TextBox>();
-
-  unsigned offset = 0;
-  std::vector<TextBox> boxes;
-  for (RenderObject* object = m_renderView.get(); object;
-       object = object->nextInPreOrder()) {
-    if (!object->isText())
-      continue;
-    RenderText* text = toRenderText(object);
-    unsigned length = text->textLength();
-    if (offset + length > start) {
-      unsigned startOffset = offset > start ? 0 : start - offset;
-      unsigned endOffset = end - offset;
-      text->appendAbsoluteTextBoxesForRange(boxes, startOffset, endOffset);
-    }
-    offset += length;
-    if (offset >= end)
-      break;
-  }
-
-  return boxes;
-}
-
-int Paragraph::absoluteOffsetForPosition(const PositionWithAffinity& position) {
-  FTL_DCHECK(position.renderer());
-  unsigned offset = 0;
-  for (RenderObject* object = m_renderView.get(); object;
-       object = object->nextInPreOrder()) {
-    if (object == position.renderer())
-      return offset + position.offset();
-    if (object->isText()) {
-      RenderText* text = toRenderText(object);
-      offset += text->textLength();
-    }
-  }
-  FTL_DCHECK(false);
-  return 0;
+  return m_paragraphImpl->getRectsForRange(start, end);
 }
 
 Dart_Handle Paragraph::getPositionForOffset(double dx, double dy) {
-  LayoutPoint point(dx, dy);
-  PositionWithAffinity position = m_renderView->positionForPoint(point);
-  Dart_Handle result = Dart_NewList(2);
-  Dart_ListSetAt(result, 0, ToDart(absoluteOffsetForPosition(position)));
-  Dart_ListSetAt(result, 1, ToDart(static_cast<int>(position.affinity())));
-  return result;
+  return m_paragraphImpl->getPositionForOffset(dx, dy);
 }
 
 Dart_Handle Paragraph::getWordBoundary(unsigned offset) {
-  String text;
-  int start = 0, end = 0;
-
-  for (RenderObject* object = m_renderView.get(); object;
-       object = object->nextInPreOrder()) {
-    if (!object->isText())
-      continue;
-    RenderText* renderText = toRenderText(object);
-    text.append(renderText->text());
-  }
-
-  TextBreakIterator* it = wordBreakIterator(text, 0, text.length());
-  if (it) {
-    end = it->following(offset);
-    if (end < 0)
-      end = it->last();
-    start = it->previous();
-  }
-
-  Dart_Handle result = Dart_NewList(2);
-  Dart_ListSetAt(result, 0, ToDart(start));
-  Dart_ListSetAt(result, 1, ToDart(end));
-  return result;
+  return m_paragraphImpl->getWordBoundary(offset);
 }
 
 }  // namespace blink

lib/ui/text/paragraph.h

@@ -6,8 +6,13 @@
 #define FLUTTER_LIB_UI_TEXT_PARAGRAPH_H_
 
 #include "flutter/lib/ui/painting/canvas.h"
+#include "flutter/lib/ui/text/paragraph_impl.h"
+#include "flutter/lib/ui/text/paragraph_impl_blink.h"
+#include "flutter/lib/ui/text/paragraph_impl_txt.h"
 #include "flutter/lib/ui/text/text_box.h"
 #include "flutter/sky/engine/core/rendering/RenderView.h"
+#include "flutter/sky/engine/wtf/PassOwnPtr.h"
+#include "flutter/third_party/txt/src/txt/paragraph.h"
 #include "lib/tonic/dart_wrappable.h"
 
 namespace tonic {
@@ -22,10 +27,15 @@ class Paragraph : public ftl::RefCountedThreadSafe<Paragraph>,
   FRIEND_MAKE_REF_COUNTED(Paragraph);
 
  public:
-  static ftl::RefPtr<Paragraph> create(PassOwnPtr<RenderView> renderView) {
+  static ftl::RefPtr<Paragraph> Create(PassOwnPtr<RenderView> renderView) {
     return ftl::MakeRefCounted<Paragraph>(renderView);
   }
 
+  static ftl::RefPtr<Paragraph> Create(
+      std::unique_ptr<txt::Paragraph> paragraph) {
+    return ftl::MakeRefCounted<Paragraph>(std::move(paragraph));
+  }
+
   ~Paragraph() override;
 
   double width();
@@ -50,12 +60,12 @@ class Paragraph : public ftl::RefCountedThreadSafe<Paragraph>,
   static void RegisterNatives(tonic::DartLibraryNatives* natives);
 
  private:
-  RenderBox* firstChildBox() const { return m_renderView->firstChildBox(); }
-
-  int absoluteOffsetForPosition(const PositionWithAffinity& position);
+  std::unique_ptr<ParagraphImpl> m_paragraphImpl;
 
   explicit Paragraph(PassOwnPtr<RenderView> renderView);
 
+  explicit Paragraph(std::unique_ptr<txt::Paragraph> paragraph);
+
   OwnPtr<RenderView> m_renderView;
 };
 

lib/ui/text/paragraph_builder.cc

@@ -4,6 +4,7 @@
 
 #include "flutter/lib/ui/text/paragraph_builder.h"
 
+#include "flutter/common/settings.h"
 #include "flutter/common/threads.h"
 #include "flutter/lib/ui/ui_dart_state.h"
 #include "flutter/sky/engine/core/rendering/RenderInline.h"
@@ -11,6 +12,12 @@
 #include "flutter/sky/engine/core/rendering/RenderText.h"
 #include "flutter/sky/engine/core/rendering/style/RenderStyle.h"
 #include "flutter/sky/engine/platform/text/LocaleToScriptMapping.h"
+#include "flutter/third_party/txt/src/txt/font_style.h"
+#include "flutter/third_party/txt/src/txt/font_weight.h"
+#include "flutter/third_party/txt/src/txt/paragraph_style.h"
+#include "flutter/third_party/txt/src/txt/text_align.h"
+#include "flutter/third_party/txt/src/txt/text_decoration.h"
+#include "flutter/third_party/txt/src/txt/text_style.h"
 #include "lib/ftl/tasks/task_runner.h"
 #include "lib/tonic/converter/dart_converter.h"
 #include "lib/tonic/dart_args.h"
@@ -95,8 +102,7 @@ void createFontForDocument(RenderStyle* style) {
   style->font().update(UIDartState::Current()->font_selector());
 }
 
-PassRefPtr<RenderStyle> decodeParagraphStyle(
-    RenderStyle* parentStyle,
+PassRefPtr<RenderStyle> decodeParagraphStyle(RenderStyle* parentStyle,
                                              tonic::Int32List& encoded,
                                              const std::string& fontFamily,
                                              double fontSize,
@@ -187,8 +193,8 @@ ftl::RefPtr<ParagraphBuilder> ParagraphBuilder::create(
     double fontSize,
     double lineHeight,
     const std::string& ellipsis) {
-  return ftl::MakeRefCounted<ParagraphBuilder>(
-      encoded, fontFamily, fontSize, lineHeight, ellipsis);
+  return ftl::MakeRefCounted<ParagraphBuilder>(encoded, fontFamily, fontSize,
+                                               lineHeight, ellipsis);
 }
 
 ParagraphBuilder::ParagraphBuilder(tonic::Int32List& encoded,
@@ -196,10 +202,46 @@ ParagraphBuilder::ParagraphBuilder(tonic::Int32List& encoded,
                                    double fontSize,
                                    double lineHeight,
                                    const std::string& ellipsis) {
+  if (!Settings::Get().using_blink) {
+    int32_t mask = encoded[0];
+    txt::ParagraphStyle style;
+    if (mask & psTextAlignMask)
+      style.text_align = txt::TextAlign(encoded[psTextAlignIndex]);
+
+    if (mask & (psFontWeightMask | psFontStyleMask | psFontFamilyMask |
+                psFontSizeMask)) {
+      if (mask & psFontWeightMask)
+        style.font_weight =
+            static_cast<txt::FontWeight>(encoded[psFontWeightIndex]);
+
+      if (mask & psFontStyleMask)
+        style.font_style =
+            static_cast<txt::FontStyle>(encoded[psFontStyleIndex]);
+
+      if (mask & psFontFamilyMask)
+        style.font_family = fontFamily;
+
+      if (mask & psFontSizeMask)
+        style.font_size = fontSize;
+    }
+
+    if (mask & psLineHeightMask)
+      style.line_height = lineHeight;
+
+    if (mask & psMaxLinesMask)
+      style.max_lines = encoded[psMaxLinesIndex];
+
+    if (mask & psEllipsisMask)
+      style.ellipsis = ellipsis;
+
+    m_paragraphBuilder.SetParagraphStyle(style);
+  } else {
+    // Blink version.
     createRenderView();
 
-  RefPtr<RenderStyle> paragraphStyle = decodeParagraphStyle(
-      m_renderView->style(), encoded, fontFamily, fontSize, lineHeight, ellipsis);
+    RefPtr<RenderStyle> paragraphStyle =
+        decodeParagraphStyle(m_renderView->style(), encoded, fontFamily,
+                             fontSize, lineHeight, ellipsis);
     encoded.Release();
 
     m_renderParagraph = new RenderParagraph();
@@ -207,13 +249,14 @@ ParagraphBuilder::ParagraphBuilder(tonic::Int32List& encoded,
 
     m_currentRenderObject = m_renderParagraph;
     m_renderView->addChild(m_currentRenderObject);
-}
+  }
+
+}  // namespace blink
 
 ParagraphBuilder::~ParagraphBuilder() {
   if (m_renderView) {
     RenderView* renderView = m_renderView.leakPtr();
-    Threads::UI()->PostTask(
-        [renderView]() { renderView->destroy(); });
+    Threads::UI()->PostTask([renderView]() { renderView->destroy(); });
   }
 }
 
@@ -224,11 +267,67 @@ void ParagraphBuilder::pushStyle(tonic::Int32List& encoded,
                                  double wordSpacing,
                                  double height) {
   FTL_DCHECK(encoded.num_elements() == 8);
-  RefPtr<RenderStyle> style = RenderStyle::create();
-  style->inheritFrom(m_currentRenderObject->style());
 
   int32_t mask = encoded[0];
 
+  if (!Settings::Get().using_blink) {
+    // Set to use the properties of the previous style if the property is not
+    // explicitly given.
+    txt::TextStyle style = m_paragraphBuilder.PeekStyle();
+
+    if (mask & tsColorMask)
+      style.color = encoded[tsColorIndex];
+
+    if (mask & tsTextDecorationMask) {
+      style.decoration =
+          static_cast<txt::TextDecoration>(encoded[tsTextDecorationIndex]);
+    }
+
+    if (mask & tsTextDecorationColorMask)
+      style.decoration_color = encoded[tsTextDecorationColorIndex];
+
+    if (mask & tsTextDecorationStyleMask)
+      style.decoration_style = static_cast<txt::TextDecorationStyle>(
+          encoded[tsTextDecorationStyleIndex]);
+
+    if (mask & tsTextBaselineMask) {
+      // TODO(abarth): Implement TextBaseline. The CSS version of this
+      // property wasn't wired up either.
+    }
+
+    if (mask & (tsFontWeightMask | tsFontStyleMask | tsFontFamilyMask |
+                tsFontSizeMask | tsLetterSpacingMask | tsWordSpacingMask)) {
+      if (mask & tsFontWeightMask)
+        style.font_weight =
+            static_cast<txt::FontWeight>(encoded[tsFontWeightIndex]);
+
+      if (mask & tsFontStyleMask)
+        style.font_style =
+            static_cast<txt::FontStyle>(encoded[tsFontStyleIndex]);
+
+      if (mask & tsFontFamilyMask)
+        style.font_family = fontFamily;
+
+      if (mask & tsFontSizeMask)
+        style.font_size = fontSize;
+
+      if (mask & tsLetterSpacingMask)
+        style.letter_spacing = letterSpacing;
+
+      if (mask & tsWordSpacingMask)
+        style.word_spacing = wordSpacing;
+    }
+
+    if (mask & tsHeightMask) {
+      style.height = height;
+    }
+
+    m_paragraphBuilder.PushStyle(style);
+  } else {
+    // Blink Version.
+    RefPtr<RenderStyle> style = RenderStyle::create();
+    style->inheritFrom(m_currentRenderObject->style());
+
     if (mask & tsColorMask)
       style->setColor(getColorFromARGB(encoded[tsColorIndex]));
 
@@ -243,8 +342,8 @@ void ParagraphBuilder::pushStyle(tonic::Int32List& encoded,
           StyleColor(getColorFromARGB(encoded[tsTextDecorationColorIndex])));
 
     if (mask & tsTextDecorationStyleMask)
-    style->setTextDecorationStyle(
-        static_cast<TextDecorationStyle>(encoded[tsTextDecorationStyleIndex]));
+      style->setTextDecorationStyle(static_cast<TextDecorationStyle>(
+          encoded[tsTextDecorationStyleIndex]));
 
     if (mask & tsTextBaselineMask) {
       // TODO(abarth): Implement TextBaseline. The CSS version of this
@@ -296,14 +395,24 @@ void ParagraphBuilder::pushStyle(tonic::Int32List& encoded,
     span->setStyle(style.release());
     m_currentRenderObject->addChild(span);
     m_currentRenderObject = span;
+  }
 }
 
 void ParagraphBuilder::pop() {
+  if (!Settings::Get().using_blink) {
+    m_paragraphBuilder.Pop();
+  } else {
+    // Blink Version.
     if (m_currentRenderObject)
       m_currentRenderObject = m_currentRenderObject->parent();
+  }
 }
 
 void ParagraphBuilder::addText(const std::string& text) {
+  if (!Settings::Get().using_blink) {
+    m_paragraphBuilder.AddText(text);
+  } else {
+    // Blink Version.
     if (!m_currentRenderObject)
       return;
     RenderText* renderText = new RenderText(String::fromUTF8(text).impl());
@@ -311,11 +420,16 @@ void ParagraphBuilder::addText(const std::string& text) {
     style->inheritFrom(m_currentRenderObject->style());
     renderText->setStyle(style.release());
     m_currentRenderObject->addChild(renderText);
+  }
 }
 
 ftl::RefPtr<Paragraph> ParagraphBuilder::build() {
   m_currentRenderObject = nullptr;
-  return Paragraph::create(m_renderView.release());
+  if (!Settings::Get().using_blink) {
+    return Paragraph::Create(m_paragraphBuilder.Build());
+  } else {
+    return Paragraph::Create(m_renderView.release());
+  }
 }
 
 void ParagraphBuilder::createRenderView() {

lib/ui/text/paragraph_builder.h

@@ -6,6 +6,9 @@
 #define FLUTTER_LIB_UI_TEXT_PARAGRAPH_BUILDER_H_
 
 #include "flutter/lib/ui/text/paragraph.h"
+#include "flutter/sky/engine/core/rendering/RenderObject.h"
+#include "flutter/sky/engine/wtf/OwnPtr.h"
+#include "flutter/third_party/txt/src/txt/paragraph_builder.h"
 #include "lib/tonic/dart_wrappable.h"
 #include "lib/tonic/typed_data/int32_list.h"
 
@@ -15,6 +18,8 @@ class DartLibraryNatives;
 
 namespace blink {
 
+class Paragraph;
+
 class ParagraphBuilder : public ftl::RefCountedThreadSafe<ParagraphBuilder>,
                          public tonic::DartWrappable {
   DEFINE_WRAPPERTYPEINFO();
@@ -35,6 +40,7 @@ class ParagraphBuilder : public ftl::RefCountedThreadSafe<ParagraphBuilder>,
                  double letterSpacing,
                  double wordSpacing,
                  double height);
+
   void pop();
 
   void addText(const std::string& text);
@@ -55,6 +61,7 @@ class ParagraphBuilder : public ftl::RefCountedThreadSafe<ParagraphBuilder>,
   OwnPtr<RenderView> m_renderView;
   RenderObject* m_renderParagraph;
   RenderObject* m_currentRenderObject;
+  txt::ParagraphBuilder m_paragraphBuilder;
 };
 
 }  // namespace blink

lib/ui/text/paragraph_impl.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 "flutter/lib/ui/text/paragraph_impl.h"
+
+namespace blink {}  // namespace blink

lib/ui/text/paragraph_impl.h

+// 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.
+
+#ifndef FLUTTER_LIB_UI_TEXT_PARAGRAPH_IMPL_H_
+#define FLUTTER_LIB_UI_TEXT_PARAGRAPH_IMPL_H_
+
+#include "flutter/lib/ui/painting/canvas.h"
+#include "flutter/lib/ui/text/text_box.h"
+
+namespace blink {
+
+class ParagraphImpl {
+ public:
+  virtual ~ParagraphImpl(){};
+
+  virtual double width() = 0;
+
+  virtual double height() = 0;
+
+  virtual double minIntrinsicWidth() = 0;
+
+  virtual double maxIntrinsicWidth() = 0;
+
+  virtual double alphabeticBaseline() = 0;
+
+  virtual double ideographicBaseline() = 0;
+
+  virtual bool didExceedMaxLines() = 0;
+
+  virtual void layout(double width) = 0;
+
+  virtual void paint(Canvas* canvas, double x, double y) = 0;
+
+  virtual std::vector<TextBox> getRectsForRange(unsigned start,
+                                                unsigned end) = 0;
+
+  virtual Dart_Handle getPositionForOffset(double dx, double dy) = 0;
+
+  virtual Dart_Handle getWordBoundary(unsigned offset) = 0;
+};
+
+}  // namespace blink
+
+#endif  // FLUTTER_LIB_UI_TEXT_PARAGRAPH_IMPL_H_

lib/ui/text/paragraph_impl_blink.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 "flutter/lib/ui/text/paragraph_impl_blink.h"
+
+#include "flutter/common/threads.h"
+#include "flutter/lib/ui/text/paragraph.h"
+#include "flutter/lib/ui/text/paragraph_impl.h"
+#include "flutter/sky/engine/core/rendering/PaintInfo.h"
+#include "flutter/sky/engine/core/rendering/RenderParagraph.h"
+#include "flutter/sky/engine/core/rendering/RenderText.h"
+#include "flutter/sky/engine/core/rendering/style/RenderStyle.h"
+#include "flutter/sky/engine/platform/fonts/FontCache.h"
+#include "flutter/sky/engine/platform/graphics/GraphicsContext.h"
+#include "flutter/sky/engine/platform/text/TextBoundaries.h"
+#include "lib/ftl/tasks/task_runner.h"
+#include "lib/tonic/converter/dart_converter.h"
+#include "lib/tonic/dart_args.h"
+#include "lib/tonic/dart_binding_macros.h"
+#include "lib/tonic/dart_library_natives.h"
+
+using tonic::ToDart;
+
+namespace blink {
+
+ParagraphImplBlink::ParagraphImplBlink(PassOwnPtr<RenderView> renderView)
+    : m_renderView(renderView) {}
+
+ParagraphImplBlink::~ParagraphImplBlink() {
+  if (m_renderView) {
+    RenderView* renderView = m_renderView.leakPtr();
+    Threads::UI()->PostTask([renderView]() { renderView->destroy(); });
+  }
+}
+
+double ParagraphImplBlink::width() {
+  return firstChildBox()->width();
+}
+
+double ParagraphImplBlink::height() {
+  return firstChildBox()->height();
+}
+
+double ParagraphImplBlink::minIntrinsicWidth() {
+  return firstChildBox()->minPreferredLogicalWidth();
+}
+
+double ParagraphImplBlink::maxIntrinsicWidth() {
+  return firstChildBox()->maxPreferredLogicalWidth();
+}
+
+double ParagraphImplBlink::alphabeticBaseline() {
+  return firstChildBox()->firstLineBoxBaseline(
+      FontBaselineOrAuto(AlphabeticBaseline));
+}
+
+double ParagraphImplBlink::ideographicBaseline() {
+  return firstChildBox()->firstLineBoxBaseline(
+      FontBaselineOrAuto(IdeographicBaseline));
+}
+
+bool ParagraphImplBlink::didExceedMaxLines() {
+  RenderBox* box = firstChildBox();
+  ASSERT(box->isRenderParagraph());
+  RenderParagraph* paragraph = static_cast<RenderParagraph*>(box);
+  return paragraph->didExceedMaxLines();
+}
+
+void ParagraphImplBlink::layout(double width) {
+  FontCachePurgePreventer fontCachePurgePreventer;
+
+  int maxWidth = LayoutUnit(width);  // Handles infinity properly.
+  m_renderView->setFrameViewSize(IntSize(maxWidth, intMaxForLayoutUnit));
+  m_renderView->layout();
+}
+
+void ParagraphImplBlink::paint(Canvas* canvas, double x, double y) {
+  SkCanvas* skCanvas = canvas->canvas();
+  if (!skCanvas)
+    return;
+
+  FontCachePurgePreventer fontCachePurgePreventer;
+
+  // Very simplified painting to allow painting an arbitrary (layer-less)
+  // subtree.
+  RenderBox* box = firstChildBox();
+  skCanvas->translate(x, y);
+
+  GraphicsContext context(skCanvas);
+  Vector<RenderBox*> layers;
+  LayoutRect bounds = box->absoluteBoundingBoxRect();
+  FTL_DCHECK(bounds.x() == 0 && bounds.y() == 0);
+  PaintInfo paintInfo(&context, enclosingIntRect(bounds), box);
+  box->paint(paintInfo, LayoutPoint(), layers);
+  // Note we're ignoring any layers encountered.
+  // TODO(abarth): Remove the concept of RenderLayers.
+
+  skCanvas->translate(-x, -y);
+}
+
+std::vector<TextBox> ParagraphImplBlink::getRectsForRange(unsigned start,
+                                                          unsigned end) {
+  if (end <= start || start == end)
+    return std::vector<TextBox>();
+
+  unsigned offset = 0;
+  std::vector<TextBox> boxes;
+  for (RenderObject* object = m_renderView.get(); object;
+       object = object->nextInPreOrder()) {
+    if (!object->isText())
+      continue;
+    RenderText* text = toRenderText(object);
+    unsigned length = text->textLength();
+    if (offset + length > start) {
+      unsigned startOffset = offset > start ? 0 : start - offset;
+      unsigned endOffset = end - offset;
+      text->appendAbsoluteTextBoxesForRange(boxes, startOffset, endOffset);
+    }
+    offset += length;
+    if (offset >= end)
+      break;
+  }
+
+  return boxes;
+}
+
+int ParagraphImplBlink::absoluteOffsetForPosition(
+    const PositionWithAffinity& position) {
+  FTL_DCHECK(position.renderer());
+  unsigned offset = 0;
+  for (RenderObject* object = m_renderView.get(); object;
+       object = object->nextInPreOrder()) {
+    if (object == position.renderer())
+      return offset + position.offset();
+    if (object->isText()) {
+      RenderText* text = toRenderText(object);
+      offset += text->textLength();
+    }
+  }
+  FTL_DCHECK(false);
+  return 0;
+}
+
+Dart_Handle ParagraphImplBlink::getPositionForOffset(double dx, double dy) {
+  LayoutPoint point(dx, dy);
+  PositionWithAffinity position = m_renderView->positionForPoint(point);
+  Dart_Handle result = Dart_NewList(2);
+  Dart_ListSetAt(result, 0, ToDart(absoluteOffsetForPosition(position)));
+  Dart_ListSetAt(result, 1, ToDart(static_cast<int>(position.affinity())));
+  return result;
+}
+
+Dart_Handle ParagraphImplBlink::getWordBoundary(unsigned offset) {
+  String text;
+  int start = 0, end = 0;
+
+  for (RenderObject* object = m_renderView.get(); object;
+       object = object->nextInPreOrder()) {
+    if (!object->isText())
+      continue;
+    RenderText* renderText = toRenderText(object);
+    text.append(renderText->text());
+  }
+
+  TextBreakIterator* it = wordBreakIterator(text, 0, text.length());
+  if (it) {
+    end = it->following(offset);
+    if (end < 0)
+      end = it->last();
+    start = it->previous();
+  }
+
+  Dart_Handle result = Dart_NewList(2);
+  Dart_ListSetAt(result, 0, ToDart(start));
+  Dart_ListSetAt(result, 1, ToDart(end));
+  return result;
+}
+
+}  // namespace blink

lib/ui/text/paragraph_impl_blink.h

+// 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.
+
+#ifndef FLUTTER_LIB_UI_TEXT_PARAGRAPH_IMPL_BLINK_H_
+#define FLUTTER_LIB_UI_TEXT_PARAGRAPH_IMPL_BLINK_H_
+
+#include "flutter/lib/ui/painting/canvas.h"
+#include "flutter/lib/ui/text/paragraph_impl.h"
+#include "flutter/lib/ui/text/text_box.h"
+#include "flutter/sky/engine/core/rendering/RenderView.h"
+#include "flutter/third_party/txt/src/txt/paragraph.h"
+
+namespace blink {
+
+class ParagraphImplBlink : public ParagraphImpl {
+ public:
+  ~ParagraphImplBlink() override;
+
+  explicit ParagraphImplBlink(PassOwnPtr<RenderView> renderView);
+
+  double width() override;
+  double height() override;
+  double minIntrinsicWidth() override;
+  double maxIntrinsicWidth() override;
+  double alphabeticBaseline() override;
+  double ideographicBaseline() override;
+  bool didExceedMaxLines() override;
+
+  void layout(double width) override;
+  void paint(Canvas* canvas, double x, double y) override;
+
+  std::vector<TextBox> getRectsForRange(unsigned start, unsigned end) override;
+  Dart_Handle getPositionForOffset(double dx, double dy) override;
+  Dart_Handle getWordBoundary(unsigned offset) override;
+
+  RenderView* renderView() const { return m_renderView.get(); }
+
+ private:
+  RenderBox* firstChildBox() const { return m_renderView->firstChildBox(); }
+
+  int absoluteOffsetForPosition(const PositionWithAffinity& position);
+
+  OwnPtr<RenderView> m_renderView;
+};
+
+}  // namespace blink
+
+#endif  // FLUTTER_LIB_UI_TEXT_PARAGRAPH_IMPL_BLINK_H_

lib/ui/text/paragraph_impl_txt.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 "flutter/lib/ui/text/paragraph_impl_txt.h"
+
+#include "flutter/common/threads.h"
+#include "flutter/lib/ui/text/paragraph.h"
+#include "flutter/lib/ui/text/paragraph_impl.h"
+#include "lib/ftl/logging.h"
+#include "lib/ftl/tasks/task_runner.h"
+#include "lib/tonic/converter/dart_converter.h"
+#include "third_party/skia/include/core/SkPoint.h"
+
+using tonic::ToDart;
+
+namespace blink {
+
+ParagraphImplTxt::ParagraphImplTxt(std::unique_ptr<txt::Paragraph> paragraph)
+    : m_paragraph(std::move(paragraph)) {}
+
+ParagraphImplTxt::~ParagraphImplTxt() {}
+
+double ParagraphImplTxt::width() {
+  return m_paragraph->GetMaxWidth();
+}
+
+double ParagraphImplTxt::height() {
+  return m_paragraph->GetHeight();
+}
+
+double ParagraphImplTxt::minIntrinsicWidth() {
+  return m_paragraph->GetMinIntrinsicWidth();
+}
+
+double ParagraphImplTxt::maxIntrinsicWidth() {
+  return m_paragraph->GetMaxIntrinsicWidth();
+}
+
+double ParagraphImplTxt::alphabeticBaseline() {
+  return m_paragraph->GetAlphabeticBaseline();
+}
+
+double ParagraphImplTxt::ideographicBaseline() {
+  return m_paragraph->GetIdeographicBaseline();
+}
+
+bool ParagraphImplTxt::didExceedMaxLines() {
+  return m_paragraph->DidExceedMaxLines();
+}
+
+void ParagraphImplTxt::layout(double width) {
+  m_width = width;
+  m_paragraph->Layout(width);
+}
+
+void ParagraphImplTxt::paint(Canvas* canvas, double x, double y) {
+  SkCanvas* sk_canvas = canvas->canvas();
+  if (!sk_canvas)
+    return;
+  m_paragraph->Paint(sk_canvas, x, y);
+}
+
+std::vector<TextBox> ParagraphImplTxt::getRectsForRange(unsigned start,
+                                                        unsigned end) {
+  std::vector<TextBox> result;
+  std::vector<SkRect> rects = m_paragraph->GetRectsForRange(start, end);
+  for (size_t i = 0; i < rects.size(); ++i) {
+    result.push_back(TextBox(rects[i], m_paragraph->GetParagraphStyle().rtl
+                                           ? TextDirection::RTL
+                                           : TextDirection::LTR));
+  }
+  return result;
+}
+
+Dart_Handle ParagraphImplTxt::getPositionForOffset(double dx, double dy) {
+  Dart_Handle result = Dart_NewList(2);
+  Dart_ListSetAt(
+      result, 0,
+      ToDart(m_paragraph->GetGlyphPositionAtCoordinate(dx, dy, true)));
+  Dart_ListSetAt(result, 1, ToDart(static_cast<int>(EAffinity::DOWNSTREAM)));
+  return result;
+}
+
+Dart_Handle ParagraphImplTxt::getWordBoundary(unsigned offset) {
+  SkIPoint point = m_paragraph->GetWordBoundary(offset);
+  Dart_Handle result = Dart_NewList(2);
+  Dart_ListSetAt(result, 0, ToDart(point.x()));
+  Dart_ListSetAt(result, 1, ToDart(point.y()));
+  return result;
+}
+
+}  // namespace blink

lib/ui/text/paragraph_impl_txt.h

+// 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.
+
+#ifndef FLUTTER_LIB_UI_TEXT_PARAGRAPH_IMPL_TXT_H_
+#define FLUTTER_LIB_UI_TEXT_PARAGRAPH_IMPL_TXT_H_
+
+#include "flutter/lib/ui/painting/canvas.h"
+#include "flutter/lib/ui/text/paragraph_impl.h"
+#include "flutter/lib/ui/text/paragraph_impl_blink.h"
+#include "flutter/lib/ui/text/text_box.h"
+#include "flutter/third_party/txt/src/txt/paragraph.h"
+
+namespace blink {
+
+class ParagraphImplTxt : public ParagraphImpl {
+ public:
+  ~ParagraphImplTxt() override;
+
+  explicit ParagraphImplTxt(std::unique_ptr<txt::Paragraph> paragraph);
+
+  double width() override;
+  double height() override;
+  double minIntrinsicWidth() override;
+  double maxIntrinsicWidth() override;
+  double alphabeticBaseline() override;
+  double ideographicBaseline() override;
+  bool didExceedMaxLines() override;
+
+  void layout(double width) override;
+  void paint(Canvas* canvas, double x, double y) override;
+
+  std::vector<TextBox> getRectsForRange(unsigned start, unsigned end) override;
+  Dart_Handle getPositionForOffset(double dx, double dy) override;
+  Dart_Handle getWordBoundary(unsigned offset) override;
+
+ private:
+  std::unique_ptr<txt::Paragraph> m_paragraph;
+  double m_width = -1.0;
+};
+
+}  // namespace blink
+
+#endif  // FLUTTER_LIB_UI_TEXT_PARAGRAPH_IMPL_TXT_H_

runtime/BUILD.gn

@@ -40,6 +40,7 @@ source_set("embedded_resources_cc") {
 }
 
 source_set("runtime") {
+
   sources = [
     "asset_font_selector.cc",
     "asset_font_selector.h",
@@ -82,6 +83,7 @@ source_set("runtime") {
     "//lib/tonic",
     "//third_party/rapidjson",
     "//third_party/skia",
+    "//flutter/third_party/txt",
   ]
 
   defines = []

runtime/asset_font_selector.cc

@@ -5,6 +5,7 @@
 #include "flutter/runtime/asset_font_selector.h"
 
 #include "flutter/assets/zip_asset_store.h"
+#include "flutter/lib/ui/text/font_collection_mgr.h"
 #include "flutter/lib/ui/ui_dart_state.h"
 #include "flutter/sky/engine/platform/fonts/FontData.h"
 #include "flutter/sky/engine/platform/fonts/FontFaceCreationParams.h"
@@ -35,6 +36,7 @@ struct AssetFontSelector::TypefaceAsset {
 };
 
 namespace {
+
 const char kFontManifestAssetPath[] = "FontManifest.json";
 
 // Weight values corresponding to the members of the FontWeight enum.
@@ -76,7 +78,8 @@ struct FontMatcher {
   const FontDescription& description_;
   int target_weight_;
 };
-}
+
+}  // namespace
 
 void AssetFontSelector::Install(ftl::RefPtr<ZipAssetStore> asset_store) {
   RefPtr<AssetFontSelector> font_selector =

shell/common/shell.cc

@@ -147,6 +147,9 @@ void Shell::InitStandalone(ftl::CommandLine command_line,
   settings.enable_software_rendering =
       command_line.HasOption(FlagForSwitch(Switch::EnableSoftwareRendering));
 
+  settings.using_blink =
+      !command_line.HasOption(FlagForSwitch(Switch::EnableTxt));
+
   settings.endless_trace_buffer =
       command_line.HasOption(FlagForSwitch(Switch::EndlessTraceBuffer));
 
@@ -242,7 +245,8 @@ void Shell::GetRasterizers(std::vector<ftl::WeakPtr<Rasterizer>>* rasterizers) {
   *rasterizers = rasterizers_;
 }
 
-void Shell::AddPlatformView(const std::shared_ptr<PlatformView>& platform_view) {
+void Shell::AddPlatformView(
+    const std::shared_ptr<PlatformView>& platform_view) {
   std::lock_guard<std::mutex> lk(platform_views_mutex_);
   if (platform_view) {
     platform_views_.push_back(platform_view);
@@ -318,7 +322,8 @@ void Shell::RunInPlatformViewUIThread(uintptr_t view_id,
 
   for (auto it = platform_views_.begin(); it != platform_views_.end(); it++) {
     std::shared_ptr<PlatformView> view = it->lock();
-    if (!view) continue;
+    if (!view)
+      continue;
     if (reinterpret_cast<uintptr_t>(view.get()) == view_id) {
       *view_existed = true;
       view->RunFromSource(assets_directory, main, packages);

shell/common/switches.h

@@ -65,6 +65,9 @@ DEF_SWITCH(EnableSoftwareRendering,
            "Enable rendering using the Skia software backend. This is useful"
            "when testing Flutter on emulators. By default, Flutter will"
            "attempt to either use OpenGL or Vulkan.")
+DEF_SWITCH(EnableTxt,
+           "enable-txt",
+           "Enable libtxt as the text shaping library instead of Blink.")
 DEF_SWITCH(FLX, "flx", "Specify the the FLX path.")
 DEF_SWITCH(Help, "help", "Display this help text.")
 DEF_SWITCH(LogTag, "log-tag", "Tag associated with log messages.")

travis/licenses_golden/licenses_flutter

@@ -9364,10 +9364,18 @@ FILE: ../../../flutter/lib/ui/painting/shader.cc
 FILE: ../../../flutter/lib/ui/painting/shader.h
 FILE: ../../../flutter/lib/ui/pointer.dart
 FILE: ../../../flutter/lib/ui/text.dart
+FILE: ../../../flutter/lib/ui/text/font_collection_mgr.cc
+FILE: ../../../flutter/lib/ui/text/font_collection_mgr.h
 FILE: ../../../flutter/lib/ui/text/paragraph.cc
 FILE: ../../../flutter/lib/ui/text/paragraph.h
 FILE: ../../../flutter/lib/ui/text/paragraph_builder.cc
 FILE: ../../../flutter/lib/ui/text/paragraph_builder.h
+FILE: ../../../flutter/lib/ui/text/paragraph_impl.cc
+FILE: ../../../flutter/lib/ui/text/paragraph_impl.h
+FILE: ../../../flutter/lib/ui/text/paragraph_impl_blink.cc
+FILE: ../../../flutter/lib/ui/text/paragraph_impl_blink.h
+FILE: ../../../flutter/lib/ui/text/paragraph_impl_txt.cc
+FILE: ../../../flutter/lib/ui/text/paragraph_impl_txt.h
 FILE: ../../../flutter/lib/ui/text/text_box.cc
 FILE: ../../../flutter/lib/ui/ui.dart
 FILE: ../../../flutter/lib/ui/ui_dart_state.cc