Sky: different tack for custom Rect type in the Canvas API.

sky/engine/core/painting/Rect.cpp

+// 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/config.h"
+#include "sky/engine/core/painting/Rect.h"
+
+#include "sky/engine/tonic/dart_error.h"
+#include "sky/engine/tonic/dart_state.h"
+#include "base/logging.h"
+
+namespace blink {
+
+// Convert dart_rect._value[0...3] ==> SkRect.
+Rect DartConverter<Rect, void>::FromArgumentsWithNullCheck(
+    Dart_NativeArguments args,
+    int index,
+    Dart_Handle& exception) {
+  Rect result;
+  result.is_null = true;
+
+  Dart_Handle dart_rect = Dart_GetNativeArgument(args, index);
+  DCHECK(!LogIfError(dart_rect));
+
+  Dart_Handle value = Dart_GetField(dart_rect,
+                                    Dart_NewStringFromCString("_value"));
+  if (Dart_IsNull(value))
+    return result;
+
+  Dart_TypedData_Type type;
+  float* data = nullptr;
+  intptr_t num_elements = 0;
+  Dart_TypedDataAcquireData(
+      value, &type, reinterpret_cast<void**>(&data), &num_elements);
+  DCHECK(!LogIfError(value));
+  ASSERT(type == Dart_TypedData_kFloat32 && num_elements == 4);
+
+  SkScalar* dest[] = {
+    &result.sk_rect.fLeft,
+    &result.sk_rect.fTop,
+    &result.sk_rect.fRight,
+    &result.sk_rect.fBottom
+  };
+  for (intptr_t i = 0; i < 4; ++i)
+    *dest[i] = data[i];
+
+  Dart_TypedDataReleaseData(value);
+
+  result.is_null = false;
+  return result;
+}
+
+} // namespace blink