Make scroll offset type of float in cc

ui/gfx/geometry/scroll_offset.h

+// Copyright 2014 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 UI_GFX_GEOMETRY_SCROLL_OFFSET_H_
+#define UI_GFX_GEOMETRY_SCROLL_OFFSET_H_
+
+#include <iosfwd>
+#include <string>
+
+#include "ui/gfx/geometry/safe_integer_conversions.h"
+#include "ui/gfx/geometry/vector2d.h"
+#include "ui/gfx/gfx_export.h"
+
+namespace gfx {
+
+class GFX_EXPORT ScrollOffset {
+ public:
+  ScrollOffset() : x_(0), y_(0) {}
+  ScrollOffset(double x, double y) : x_(x), y_(y) {}
+  explicit ScrollOffset(const Vector2dF& v) : x_(v.x()), y_(v.y()) {}
+  explicit ScrollOffset(const Vector2d& v) : x_(v.x()), y_(v.y()) {}
+
+  double x() const { return x_; }
+  void set_x(double x) { x_ = x; }
+
+  double y() const { return y_; }
+  void set_y(double y) { y_ = y; }
+
+  // True if both components are 0.
+  bool IsZero() const;
+
+  // Add the components of the |other| ScrollOffset to the current ScrollOffset.
+  void Add(const ScrollOffset& other);
+  // Subtract the components of the |other| ScrollOffset from the current
+  // ScrollOffset.
+  void Subtract(const ScrollOffset& other);
+
+  void operator+=(const ScrollOffset& other) { Add(other); }
+  void operator-=(const ScrollOffset& other) { Subtract(other); }
+
+  void SetToMin(const ScrollOffset& other) {
+    x_ = x_ <= other.x_ ? x_ : other.x_;
+    y_ = y_ <= other.y_ ? y_ : other.y_;
+  }
+
+  void SetToMax(const ScrollOffset& other) {
+    x_ = x_ >= other.x_ ? x_ : other.x_;
+    y_ = y_ >= other.y_ ? y_ : other.y_;
+  }
+
+  void Scale(double scale) { Scale(scale, scale); }
+  void Scale(double x_scale, double y_scale) {
+    x_ *= x_scale;
+    y_ *= y_scale;
+  }
+
+  std::string ToString() const;
+
+ private:
+  double x_;
+  double y_;
+};
+
+inline bool operator==(const ScrollOffset& lhs, const ScrollOffset& rhs) {
+  return lhs.x() == rhs.x() && lhs.y() == rhs.y();
+}
+
+inline bool operator!=(const ScrollOffset& lhs, const ScrollOffset& rhs) {
+  return lhs.x() != rhs.x() || lhs.y() != rhs.y();
+}
+
+inline ScrollOffset operator-(const ScrollOffset& v) {
+  return ScrollOffset(-v.x(), -v.y());
+}
+
+inline ScrollOffset operator+(const ScrollOffset& lhs,

[danakj, 2014/09/27 00:00:44]

can we remove the operator+? Seems like ScrollOffsetWithDelta() covers most of
the uses, and we can use Add() for the relatively few (any?) leftovers

[Yufeng Shen (Slow to review), 2014/09/29 19:27:34]

LayerTreeImpl::GetDelegatedScrollOffset() has some use cases where
inner/outer_view_port
scroll offset are added/subtracted. Using Add/Subtract would work, but
Add/Subtract is changing the caller'
s value and we often just want a temporary sum value, operator+ and operator-
seems does the work well.

+                              const ScrollOffset& rhs) {
+  ScrollOffset result = lhs;
+  result.Add(rhs);
+  return result;
+}
+
+inline ScrollOffset operator-(const ScrollOffset& lhs,
+                              const ScrollOffset& rhs) {
+  ScrollOffset result = lhs;
+  result.Add(-rhs);
+  return result;
+}
+
+inline Vector2d ScrollOffsetToFlooredVector2d(const ScrollOffset& v) {
+  return Vector2d(ToFlooredInt(v.x()), ToFlooredInt(v.y()));
+}
+
+inline Vector2dF ScrollOffsetToVector2dF(const ScrollOffset& v) {
+  return Vector2dF(v.x(), v.y());
+}
+
+inline ScrollOffset ScrollOffsetWithDelta(const ScrollOffset& offset,
+                                          const Vector2dF& delta) {
+  return ScrollOffset(offset.x() + delta.x(),
+                      offset.y() + delta.y());
+}
+
+// This is declared here for use in gtest-based unit tests but is defined in
+// the gfx_test_support target. Depend on that to use this in your unit test.
+// This should not be used in production code - call ToString() instead.
+void PrintTo(const ScrollOffset& scroll_offset, ::std::ostream* os);
+
+}  // namespace gfx
+
+#endif  // UI_GFX_GEOMETRY_SCROLL_OFFSET_H_