Sky: Add a Point class.

sky/engine/core/painting/Point.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/Point.h"
+
+#include "sky/engine/tonic/dart_error.h"
+#include "sky/engine/tonic/dart_state.h"
+#include "base/logging.h"
+
+namespace blink {
+
+// Convert dartPoint.x,y ==> SkPoint.
+Point DartConverter<Point, void>::FromArgumentsWithNullCheck(
+    Dart_NativeArguments args,
+    int index,
+    Dart_Handle& exception) {
+  Point result;
+  result.isNull = true;
+
+  Dart_Handle dartPoint = Dart_GetNativeArgument(args, index);
+  DCHECK(!LogIfError(dartPoint));
+
+  Dart_Handle xValue = Dart_GetField(dartPoint, Dart_NewStringFromCString("x"));
+  Dart_Handle yValue = Dart_GetField(dartPoint, Dart_NewStringFromCString("y"));

[abarth-chromium, 2015/05/27 02:17:36]

We should cache the "x" and "y" strings so that we don't have to malloc up new
strings each time we want to convert a point.  We probably want to use Symbols
rather than strings as well for added speed.

[Matt Perry, 2015/05/27 17:55:43]

OK. Not sure what you mean by Symbols. Do we have code that does that?

+
+  double x = 0.0, y = 0.0;
+  Dart_DoubleValue(xValue, &x);
+  Dart_Handle err = Dart_DoubleValue(xValue, &y);

[abarth-chromium, 2015/05/27 02:17:36]

Why do we capture an error for y and not for x?

[Matt Perry, 2015/05/27 17:55:43]

I was thinking the error would propagate to the last API call, but I guess that
doesn't make sense. (Does that happen if I call Dart_Foo(handle) if handle has
an error?)

+  DCHECK(!LogIfError(err));
+  result.skPoint.set(x, y);
+  result.isNull = false;
+  return result;
+}
+
+} // namespace blink