Introduce TextBox

TextBox is a rect that understands TextDirection.

sky/engine/bindings/dart_vm_entry_points.txt

@@ -36,6 +36,7 @@ dart:ui,RRect,RRect.
 dart:ui,Scene,Scene.
 dart:ui,SceneBuilder,SceneBuilder.
 dart:ui,Shader,Shader.
+dart:ui,TextBox,TextBox._
 dart:ui,Tracing,Tracing.
 dart:ui,VelocityTracker,VelocityTracker.
 dart:ui,WheelEvent,WheelEvent.

sky/engine/core/core.gni

@@ -214,6 +214,8 @@ sky_core_files = [
   "text/Paragraph.h",
   "text/ParagraphBuilder.cpp",
   "text/ParagraphBuilder.h",
+  "text/TextBox.cpp",
+  "text/TextBox.h",
   "window/window.cc",
   "window/window.h",
 ]

sky/engine/core/dart/text.dart

@@ -394,6 +394,89 @@ class ParagraphStyle {
   }
 }
 
+/// A direction in which text flows.
+enum TextDirection {
+  /// The text flows from right to left (e.g. Arabic, Hebrew).
+  rtl,
+
+  /// The text flows from left to right (e.g., English, French).
+  ltr
+}
+
+/// A rectangle enclosing a run of text.
+class TextBox {
+  const TextBox.fromLTRBD(
+    this.left,
+    this.top,
+    this.right,
+    this.bottom,
+    this.direction
+  );
+
+  TextBox._(
+    this.left,
+    this.top,
+    this.right,
+    this.bottom,
+    int directionIndex
+  ) : direction = TextDirection.values[directionIndex];
+
+  /// The left edge of the text box, irrespective of direction.
+  final double left;
+
+  /// The top edge of the text box.
+  final double top;
+
+  /// The right edge of the text box, irrespective of direction.
+  final double right;
+
+  /// The bottom edge of the text box.
+  final double bottom;
+
+  /// The direction in which text inside this box flows.
+  final TextDirection direction;
+
+  /// Returns a rect of the same size as this box.
+  Rect toRect() => new Rect.fromLTRB(left, top, right, bottom);
+
+  /// The left edge of the box for ltr text; the right edge of the box for rtl text.
+  double get start {
+    switch (direction) {
+      case TextDirection.rtl:
+        return right;
+      case TextDirection.ltr:
+        return left;
+    }
+  }
+
+  /// The right edge of the box for ltr text; the left edge of the box for rtl text.
+  double get end {
+    switch (direction) {
+      case TextDirection.rtl:
+        return left;
+      case TextDirection.ltr:
+        return right;
+    }
+  }
+
+  bool operator ==(dynamic other) {
+    if (identical(this, other))
+      return true;
+    if (other is! TextBox)
+      return false;
+    final TextBox typedOther = other;
+    return typedOther.left == left
+        && typedOther.top == top
+        && typedOther.right == right
+        && typedOther.bottom == bottom
+        && typedOther.direction == direction;
+  }
+
+  int get hashCode => hashValues(left, top, right, bottom, direction);
+
+  String toString() => "TextBox.fromLTRBD(${left.toStringAsFixed(1)}, ${top.toStringAsFixed(1)}, ${right.toStringAsFixed(1)}, ${bottom.toStringAsFixed(1)}, $direction)";
+}
+
 abstract class Paragraph extends NativeFieldWrapperClass2 {
   double get minWidth native "Paragraph_minWidth";
   void set minWidth(double value) native "Paragraph_setMinWidth";
@@ -413,7 +496,7 @@ abstract class Paragraph extends NativeFieldWrapperClass2 {
   void layout() native "Paragraph_layout";
   void paint(Canvas canvas, Offset offset) native "Paragraph_paint";
 
-  List<Rect> getRectsForRange(int start, int end) native "Paragraph_getRectsForRange";
+  List<TextBox> getBoxesForRange(int start, int end) native "Paragraph_getRectsForRange";
 }
 
 class ParagraphBuilder extends NativeFieldWrapperClass2 {

sky/engine/core/text/Paragraph.cpp

@@ -110,9 +110,9 @@ void Paragraph::paint(Canvas* canvas, const Offset& offset)
     skCanvas->translate(-offset.sk_size.width(), -offset.sk_size.height());
 }
 
-std::vector<Rect> Paragraph::getRectsForRange(unsigned start, unsigned end) {
+std::vector<TextBox> Paragraph::getRectsForRange(unsigned start, unsigned end) {
   if (end <= start || start == end)
-    return std::vector<Rect>();
+    return std::vector<TextBox>();
 
   unsigned offset = 0;
   Vector<IntRect> rects;
@@ -131,10 +131,12 @@ std::vector<Rect> Paragraph::getRectsForRange(unsigned start, unsigned end) {
       break;
   }
 
-  std::vector<Rect> result;
+  std::vector<TextBox> result;
   result.reserve(rects.size());
-  for (auto& rect : rects)
-    result.emplace_back(rect);
+  for (auto& rect : rects) {
+    // TODO(abarth): Actually figure out the direction of the box.
+    result.emplace_back(rect, LTR);
+  }
 
   return result;
 }

sky/engine/core/text/Paragraph.h

@@ -11,6 +11,7 @@
 #include "sky/engine/core/painting/Canvas.h"
 #include "sky/engine/core/painting/Offset.h"
 #include "sky/engine/core/rendering/RenderView.h"
+#include "sky/engine/core/text/TextBox.h"
 
 namespace blink {
 class DartLibraryNatives;
@@ -46,7 +47,7 @@ public:
     void layout();
     void paint(Canvas* canvas, const Offset& offset);
 
-    std::vector<Rect> getRectsForRange(unsigned start, unsigned end);
+    std::vector<TextBox> getRectsForRange(unsigned start, unsigned end);
 
     RenderView* renderView() const { return m_renderView.get(); }
 

sky/engine/core/text/TextBox.cpp

@@ -0,0 +1,32 @@
+// 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 "sky/engine/core/text/TextBox.h"
+
+#include "base/logging.h"
+#include "sky/engine/core/script/dom_dart_state.h"
+#include "sky/engine/tonic/dart_class_library.h"
+#include "sky/engine/tonic/dart_error.h"
+
+namespace blink {
+
+Dart_Handle DartConverter<TextBox>::ToDart(const TextBox& val) {
+  if (val.is_null)
+    return Dart_Null();
+  DartClassLibrary& class_library = DartState::Current()->class_library();
+  Dart_Handle type = Dart_HandleFromPersistent(
+      class_library.GetClass("ui", "TextBox"));
+  DCHECK(!LogIfError(type));
+  const int argc = 5;
+  Dart_Handle argv[argc] = {
+    blink::ToDart(val.sk_rect.fLeft),
+    blink::ToDart(val.sk_rect.fTop),
+    blink::ToDart(val.sk_rect.fRight),
+    blink::ToDart(val.sk_rect.fBottom),
+    blink::ToDart(static_cast<int>(val.direction)),
+  };
+  return Dart_New(type, blink::ToDart("_"), argc, argv);
+}
+
+} // namespace blink

sky/engine/core/text/TextBox.h

@@ -0,0 +1,33 @@
+// Copyright 2016 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 SKY_ENGINE_CORE_TEXT_TEXT_BOX_H_
+#define SKY_ENGINE_CORE_TEXT_TEXT_BOX_H_
+
+#include "dart/runtime/include/dart_api.h"
+#include "sky/engine/platform/text/TextDirection.h"
+#include "sky/engine/tonic/dart_converter.h"
+#include "third_party/skia/include/core/SkRect.h"
+
+namespace blink {
+
+class TextBox {
+ public:
+  TextBox() : is_null(true) { }
+  TextBox(SkRect r, TextDirection direction)
+    : sk_rect(std::move(r)), direction(direction), is_null(false) { }
+
+  SkRect sk_rect;
+  TextDirection direction;
+  bool is_null;
+};
+
+template <>
+struct DartConverter<TextBox> {
+  static Dart_Handle ToDart(const TextBox& val);
+};
+
+} // namespace blink
+
+#endif  // SKY_ENGINE_CORE_TEXT_TEXT_BOX_H_