Add overscroll edge effect animations for Android.

content/browser/android/overscroll_glow.cc

Index: content/browser/android/overscroll_glow.cc
diff --git a/content/browser/android/overscroll_glow.cc b/content/browser/android/overscroll_glow.cc
new file mode 100644
index 0000000000000000000000000000000000000000..39478f47bebccf27f4622e2db2caa26ff2bec740
--- /dev/null
+++ b/content/browser/android/overscroll_glow.cc
@@ -0,0 +1,263 @@
+// Copyright (c) 2013 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/browser/android/overscroll_glow.h"
+
+#include "base/lazy_instance.h"
+#include "cc/layers/image_layer.h"
+#include "content/browser/android/edge_effect.h"
+#include "skia/ext/image_operations.h"
+#include "ui/gfx/android/java_bitmap.h"
+
+using std::max;
+using std::min;
+
+namespace content {
+
+namespace {
+
+const float kEpsilon = 1e-3f;
+
+SkBitmap CreateBitmap(const char* resource, gfx::Size size) {
+  SkBitmap bitmap = gfx::CreateSkBitmapFromResource(resource);
+  if (bitmap.isNull())
+    return bitmap;
+  return skia::ImageOperations::Resize(bitmap,
+                                       skia::ImageOperations::RESIZE_GOOD,
+                                       size.width(), size.height());
+}
+
+class OverscrollResources {
+ public:
+  OverscrollResources()
+    : edge_bitmap_(CreateBitmap("android:drawable/overscroll_edge",
+                                gfx::Size(256, 12))),
+      glow_bitmap_(CreateBitmap("android:drawable/overscroll_glow",
+                                gfx::Size(128, 128))) {
+  }
+
+  const SkBitmap& edge_bitmap() { return edge_bitmap_; }
+  const SkBitmap& glow_bitmap() { return glow_bitmap_; }
+
+ private:
+  SkBitmap edge_bitmap_;
+  SkBitmap glow_bitmap_;
+
+  DISALLOW_COPY_AND_ASSIGN(OverscrollResources);
+};
+
+base::LazyInstance<OverscrollResources> g_overscroll_resources =
+    LAZY_INSTANCE_INITIALIZER;
+
+scoped_refptr<cc::Layer> CreateImageLayer(const SkBitmap& bitmap) {
+  scoped_refptr<cc::ImageLayer> layer = cc::ImageLayer::Create();
+  layer->SetBitmap(bitmap);
+  return layer;
+}
+
+bool IsApproxZero(float value) {
+  return std::abs(value) < kEpsilon;
+}
+
+bool IsApproxZero(gfx::Vector2dF vector) {
+  return IsApproxZero(vector.x()) && IsApproxZero(vector.y());
+}
+
+gfx::Vector2dF ZeroSmallComponents(gfx::Vector2dF vector) {
+  if (IsApproxZero(vector.x()))
+    vector.set_x(0);
+  if (IsApproxZero(vector.y()))
+    vector.set_y(0);
+  return vector;
+}
+
+} // namespace
+
+scoped_ptr<OverscrollGlow> OverscrollGlow::Create() {
+  const SkBitmap& edge = g_overscroll_resources.Get().edge_bitmap();
+  const SkBitmap& glow = g_overscroll_resources.Get().glow_bitmap();
+  if (edge.isNull() || glow.isNull())
+    return scoped_ptr<OverscrollGlow>();
+
+  return make_scoped_ptr(new OverscrollGlow(edge, glow));
+}
+
+OverscrollGlow::OverscrollGlow(const SkBitmap& edge, const SkBitmap& glow)
+  : horizontal_overscroll_enabled_(true),
+    vertical_overscroll_enabled_(true),
+    root_layer_(cc::Layer::Create()) {
+  for (size_t i = 0; i < EdgeEffect::EDGE_COUNT; ++i) {
+    scoped_refptr<cc::Layer> edge_layer = CreateImageLayer(edge);
+    scoped_refptr<cc::Layer> glow_layer = CreateImageLayer(glow);
+    root_layer_->AddChild(edge_layer);
+    root_layer_->AddChild(glow_layer);
+    edge_effects_[i] = make_scoped_ptr(new EdgeEffect(edge_layer, glow_layer));
+  }
+}
+
+OverscrollGlow::~OverscrollGlow() {
+  root_layer_->RemoveFromParent();
+}
+
+void OverscrollGlow::OnOverscrolled(base::TimeTicks current_time,
+                                    gfx::Vector2dF overscroll,
+                                    gfx::Vector2dF velocity) {
+  // The size of the glow determines the relative effect of the inputs; an
+  // empty-sized effect is effectively disabled.
+  if (size_.IsEmpty())
+    return;
+
+  if (!horizontal_overscroll_enabled_) {
+    overscroll.set_x(0);
+    velocity.set_x(0);
+  }
+  if (!vertical_overscroll_enabled_) {
+    overscroll.set_y(0);
+    velocity.set_y(0);
+  }
+
+  // Ignore sufficiently small values that won't meaningfuly affect animation.
+  overscroll = ZeroSmallComponents(overscroll);
+  velocity = ZeroSmallComponents(velocity);
+
+  if (overscroll.IsZero()) {
+    Release(current_time);
+    return;
+  }
+
+  if (!velocity.IsZero()) {
+    // Release effects if scrolling has changed directions.
+    if (velocity.x() * old_velocity_.x() < 0)
+      Release(AXIS_X, current_time);
+    if (velocity.y() * old_velocity_.y() < 0)
+      Release(AXIS_Y, current_time);
+
+    Absorb(current_time, velocity, overscroll, old_overscroll_);
+  } else {
+    // Release effects when overscroll accumulation violates monotonicity.
+    if (overscroll.x() * old_overscroll_.x() < 0 ||
+        std::abs(overscroll.x()) < std::abs(old_overscroll_.x()))
+      Release(AXIS_X, current_time);
+    if (overscroll.y() * old_overscroll_.y() < 0 ||
+        std::abs(overscroll.y()) < std::abs(old_overscroll_.y()))
+      Release(AXIS_Y, current_time);
+
+    Pull(current_time, overscroll - old_overscroll_);
+  }
+
+  old_velocity_ = velocity;
+  old_overscroll_ = overscroll;
+}
+
+bool OverscrollGlow::Animate(base::TimeTicks current_time) {
+  if (!IsActive())
+    return false;
+
+  const gfx::SizeF sizes[EdgeEffect::EDGE_COUNT] = {
+    size_, gfx::SizeF(size_.height(), size_.width()),
+    size_, gfx::SizeF(size_.height(), size_.width())
+  };
+
+  for (size_t i = 0; i < EdgeEffect::EDGE_COUNT; ++i) {
+    if (edge_effects_[i]->Update(current_time)) {
+      edge_effects_[i]->ApplyToLayers(sizes[i],
+                                      static_cast<EdgeEffect::Edge>(i));
+    }
+  }
+
+  return IsActive();
+}
+
+bool OverscrollGlow::IsActive() const {
+  for (size_t i = 0; i < EdgeEffect::EDGE_COUNT; ++i) {
+    if (!edge_effects_[i]->IsFinished())
+      return true;
+  }
+  return false;
+}
+
+void OverscrollGlow::Finish() {
+  for (size_t i = 0; i < EdgeEffect::EDGE_COUNT; ++i)
+    edge_effects_[i]->Finish();
+}
+
+void OverscrollGlow::Pull(base::TimeTicks current_time,
+                          gfx::Vector2dF overscroll_delta) {
+  overscroll_delta = ZeroSmallComponents(overscroll_delta);
+  if (overscroll_delta.IsZero())
+    return;
+
+  gfx::Vector2dF overscroll_pull = gfx::ScaleVector2d(overscroll_delta,
+                                                      1.f / size_.width(),
+                                                      1.f / size_.height());
+  float edge_overscroll_pull[EdgeEffect::EDGE_COUNT] = {
+    min(overscroll_pull.y(), 0.f), // Top
+    min(overscroll_pull.x(), 0.f), // Left
+    max(overscroll_pull.y(), 0.f), // Bottom
+    max(overscroll_pull.x(), 0.f)  // Right
+  };
+
+  for (size_t i = 0; i < EdgeEffect::EDGE_COUNT; ++i) {
+    if (!edge_overscroll_pull[i])
+      continue;
+
+    edge_effects_[i]->Pull(current_time, std::abs(edge_overscroll_pull[i]));
+    GetOppositeEdge(i)->Release(current_time);
+  }
+}
+
+void OverscrollGlow::Absorb(base::TimeTicks current_time,
+                            gfx::Vector2dF velocity,
+                            gfx::Vector2dF overscroll,
+                            gfx::Vector2dF old_overscroll) {
+  if (overscroll.IsZero() || velocity.IsZero())
+    return;
+
+  // Only trigger on initial overscroll at a non-zero velocity
+  const float overscroll_velocities[EdgeEffect::EDGE_COUNT] = {
+    old_overscroll.y() >= 0 && overscroll.y() < 0 ? min(velocity.y(), 0.f) : 0,
+    old_overscroll.x() >= 0 && overscroll.x() < 0 ? min(velocity.x(), 0.f) : 0,
+    old_overscroll.y() <= 0 && overscroll.y() > 0 ? max(velocity.y(), 0.f) : 0,
+    old_overscroll.x() <= 0 && overscroll.x() > 0 ? max(velocity.x(), 0.f) : 0
+  };
+
+  for (size_t i = 0; i < EdgeEffect::EDGE_COUNT; ++i) {
+    if (!overscroll_velocities[i])
+      continue;
+
+    edge_effects_[i]->Absorb(current_time, std::abs(overscroll_velocities[i]));
+    GetOppositeEdge(i)->Release(current_time);
+  }
+}
+
+void OverscrollGlow::Release(base::TimeTicks current_time) {
+  for (size_t i = 0; i < EdgeEffect::EDGE_COUNT; ++i) {
+    edge_effects_[i]->Release(current_time);
+  }
+  old_overscroll_ = old_velocity_ = gfx::Vector2dF();
+}
+
+void OverscrollGlow::Release(Axis axis, base::TimeTicks current_time) {
+  switch (axis) {
+    case AXIS_X:
+      edge_effects_[EdgeEffect::EDGE_LEFT]->Release(current_time);
+      edge_effects_[EdgeEffect::EDGE_RIGHT]->Release(current_time);
+      old_overscroll_.set_x(0);
+      old_velocity_.set_x(0);
+      break;
+    case AXIS_Y:
+      edge_effects_[EdgeEffect::EDGE_TOP]->Release(current_time);
+      edge_effects_[EdgeEffect::EDGE_BOTTOM]->Release(current_time);
+      old_overscroll_.set_y(0);
+      old_velocity_.set_y(0);
+      break;
+  };
+}
+
+EdgeEffect* OverscrollGlow::GetOppositeEdge(int edge_index) {
+  return edge_effects_[(edge_index + 2) % EdgeEffect::EDGE_COUNT].get();
+}
+
+}  // namespace content
+