Consolidate content fling implementations

content/child/web_gesture_curve_impl.cc

+// 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.
+
+#include "content/child/web_gesture_curve_impl.h"
+
+#include "base/logging.h"
+#include "third_party/WebKit/public/platform/WebFloatSize.h"
+#include "third_party/WebKit/public/platform/WebGestureCurveTarget.h"
+#include "ui/events/gestures/fling_curve.h"
+#include "ui/gfx/vector2d.h"
+
+#if defined(OS_ANDROID)
+#include "ui/events/android/scroller.h"
+#endif
+
+using blink::WebGestureCurve;
+
+namespace content {
+namespace {
+
+scoped_ptr<ui::GestureCurve> CreateDefaultPlatformCurve(
+    const gfx::Vector2dF& initial_velocity) {
+  DCHECK(!initial_velocity.IsZero());
+#if defined(OS_ANDROID)
+  auto scroller = make_scoped_ptr(new ui::Scroller(ui::Scroller::Config()));
+  scroller->Fling(0,
+                  0,
+                  initial_velocity.x(),
+                  initial_velocity.y(),
+                  INT_MIN,
+                  INT_MAX,
+                  INT_MIN,
+                  INT_MAX,
+                  base::TimeTicks());
+  return scroller.PassAs<ui::GestureCurve>();
+#else
+  return scoped_ptr<ui::GestureCurve>(
+      new ui::FlingCurve(initial_velocity, base::TimeTicks()));
+#endif
+}
+
+}  // namespace
+
+// static
+scoped_ptr<WebGestureCurve> WebGestureCurveImpl::CreateFromDefaultPlatformCurve(
+    const gfx::Vector2dF& initial_velocity,
+    const gfx::Vector2dF& initial_offset) {
+  return CreateFrom(CreateDefaultPlatformCurve(initial_velocity),
+                    initial_offset);
+}
+
+// static
+scoped_ptr<WebGestureCurve> WebGestureCurveImpl::CreateFrom(
+    scoped_ptr<ui::GestureCurve> curve,
+    const gfx::Vector2dF& initial_offset) {
+  return scoped_ptr<WebGestureCurve>(
+      new WebGestureCurveImpl(curve.Pass(), initial_offset));
+}
+
+WebGestureCurveImpl::WebGestureCurveImpl(scoped_ptr<ui::GestureCurve> curve,
+                                         const gfx::Vector2dF& initial_offset)
+    : curve_(curve.Pass()), last_offset_(initial_offset) {
+}
+
+WebGestureCurveImpl::~WebGestureCurveImpl() {
+}
+
+bool WebGestureCurveImpl::apply(double time,
+                                blink::WebGestureCurveTarget* target) {
+  // If the fling has yet to start, simply return and report true to prevent
+  // fling termination.
+  if (time <= 0)
+    return true;
+
+  const base::TimeTicks time_ticks =
+      base::TimeTicks() + base::TimeDelta::FromSecondsD(time);
+  gfx::Vector2dF offset, velocity;
+  bool still_active =
+      curve_->ComputeScrollOffset(time_ticks, &offset, &velocity);
+
+  gfx::Vector2dF delta = offset - last_offset_;
+  last_offset_ = offset;
+
+  // As successive timestamps can be arbitrarily close (but monotonic!), don't
+  // assume that a zero delta means the curve has terminated.
+  if (delta.IsZero())
+    return still_active;
+
+  // scrollBy() could delete this curve if the animation is over, so don't touch
+  // any member variables after making that call.
+  bool did_scroll = target->scrollBy(blink::WebFloatSize(delta),
+                                     blink::WebFloatSize(velocity));
+  return did_scroll && still_active;
+}
+
+}  // namespace content