ui/android/edge_effect.cc - chromium/src - Git at Google

 // 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 "ui/android/edge_effect.h"

 #include "base/macros.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/ui_resource_layer.h"
 #include "ui/android/animation_utils.h"
 #include "ui/android/resources/resource_manager.h"
 #include "ui/android/resources/system_ui_resource_type.h"
 #include "ui/android/window_android_compositor.h"

 namespace ui {

 namespace {

 const ui::SystemUIResourceType kEdgeResourceId = ui::OVERSCROLL_EDGE;
 const ui::SystemUIResourceType kGlowResourceId = ui::OVERSCROLL_GLOW;

 // Time it will take the effect to fully recede in ms
 const int kRecedeTimeMs = 1000;

 // Time it will take before a pulled glow begins receding in ms
 const int kPullTimeMs = 167;

 // Time it will take in ms for a pulled glow to decay before release
 const int kPullDecayTimeMs = 1000;

 const float kMaxAlpha = 1.f;
 const float kHeldEdgeScaleY = .5f;

 const float kMaxGlowHeight = 4.f;

 const float kPullGlowBegin = 1.f;
 const float kPullEdgeBegin = 0.6f;

 // Min/max velocity that will be absorbed
 const float kMinVelocity = 100.f;
 const float kMaxVelocity = 10000.f;

 const float kEpsilon = 0.001f;

 const float kGlowHeightWidthRatio = 0.25f;

 // How much dragging should effect the height of the edge image.
 // Number determined by user testing.
 const int kPullDistanceEdgeFactor = 7;

 // How much dragging should effect the height of the glow image.
 // Number determined by user testing.
 const int kPullDistanceGlowFactor = 7;
 const float kPullDistanceAlphaGlowFactor = 1.1f;

 const int kVelocityEdgeFactor = 8;
 const int kVelocityGlowFactor = 12;

 const float kEdgeHeightAtMdpi = 12.f;
 const float kGlowHeightAtMdpi = 128.f;

 }  // namespace

 class EdgeEffect::EffectLayer {
  public:
   EffectLayer(ui::SystemUIResourceType resource_type,
               ui::ResourceManager* resource_manager)
       : ui_resource_layer_(cc::UIResourceLayer::Create()),
         resource_type_(resource_type),
         resource_manager_(resource_manager) {}

   ~EffectLayer() { ui_resource_layer_->RemoveFromParent(); }

   void SetParent(cc::Layer* parent) {
     if (ui_resource_layer_->parent() != parent)
       parent->AddChild(ui_resource_layer_);
   }

   void Disable() { ui_resource_layer_->SetIsDrawable(false); }

   void Update(const gfx::Size& size,
               const gfx::Transform& transform,
               float opacity) {
     ui_resource_layer_->SetUIResourceId(resource_manager_->GetUIResourceId(
         ui::ANDROID_RESOURCE_TYPE_SYSTEM, resource_type_));
     ui_resource_layer_->SetIsDrawable(true);
     ui_resource_layer_->SetTransformOrigin(
         gfx::Point3F(size.width() * 0.5f, 0, 0));
     ui_resource_layer_->SetTransform(transform);
     ui_resource_layer_->SetBounds(size);
     ui_resource_layer_->SetOpacity(Clamp(opacity, 0.f, 1.f));
   }

   scoped_refptr<cc::UIResourceLayer> ui_resource_layer_;
   ui::SystemUIResourceType resource_type_;
   ui::ResourceManager* resource_manager_;

   DISALLOW_COPY_AND_ASSIGN(EffectLayer);
 };

 EdgeEffect::EdgeEffect(ui::ResourceManager* resource_manager,
                        float device_scale_factor)
     : edge_(new EffectLayer(kEdgeResourceId, resource_manager)),
       glow_(new EffectLayer(kGlowResourceId, resource_manager)),
       base_edge_height_(kEdgeHeightAtMdpi * device_scale_factor),
       base_glow_height_(kGlowHeightAtMdpi * device_scale_factor),
       edge_alpha_(0),
       edge_scale_y_(0),
       glow_alpha_(0),
       glow_scale_y_(0),
       edge_alpha_start_(0),
       edge_alpha_finish_(0),
       edge_scale_y_start_(0),
       edge_scale_y_finish_(0),
       glow_alpha_start_(0),
       glow_alpha_finish_(0),
       glow_scale_y_start_(0),
       glow_scale_y_finish_(0),
       state_(STATE_IDLE),
       pull_distance_(0) {
 }

 EdgeEffect::~EdgeEffect() {
 }

 bool EdgeEffect::IsFinished() const {
   return state_ == STATE_IDLE;
 }

 void EdgeEffect::Finish() {
   edge_->Disable();
   glow_->Disable();
   pull_distance_ = 0;
   state_ = STATE_IDLE;
 }

 void EdgeEffect::Pull(base::TimeTicks current_time,
                       float delta_distance,
                       float displacement) {
   if (state_ == STATE_PULL_DECAY && current_time - start_time_ < duration_) {
     return;
   }
   if (state_ != STATE_PULL) {
     glow_scale_y_ = kPullGlowBegin;
   }
   state_ = STATE_PULL;

   start_time_ = current_time;
   duration_ = base::TimeDelta::FromMilliseconds(kPullTimeMs);

   float abs_delta_distance = std::abs(delta_distance);
   pull_distance_ += delta_distance;
   float distance = std::abs(pull_distance_);

   edge_alpha_ = edge_alpha_start_ = Clamp(distance, kPullEdgeBegin, kMaxAlpha);
   edge_scale_y_ = edge_scale_y_start_ =
       Clamp(distance * kPullDistanceEdgeFactor, kHeldEdgeScaleY, 1.f);

   glow_alpha_ = glow_alpha_start_ =
       std::min(kMaxAlpha,
                glow_alpha_ + abs_delta_distance * kPullDistanceAlphaGlowFactor);

   float glow_change = abs_delta_distance;
   if (delta_distance > 0 && pull_distance_ < 0)
     glow_change = -glow_change;
   if (pull_distance_ == 0)
     glow_scale_y_ = 0;

   // Do not allow glow to get larger than kMaxGlowHeight.
   glow_scale_y_ = glow_scale_y_start_ =
       Clamp(glow_scale_y_ + glow_change * kPullDistanceGlowFactor,
             0.f,
             kMaxGlowHeight);

   edge_alpha_finish_ = edge_alpha_;
   edge_scale_y_finish_ = edge_scale_y_;
   glow_alpha_finish_ = glow_alpha_;
   glow_scale_y_finish_ = glow_scale_y_;
 }

 void EdgeEffect::Release(base::TimeTicks current_time) {
   pull_distance_ = 0;

   if (state_ != STATE_PULL && state_ != STATE_PULL_DECAY)
     return;

   state_ = STATE_RECEDE;
   edge_alpha_start_ = edge_alpha_;
   edge_scale_y_start_ = edge_scale_y_;
   glow_alpha_start_ = glow_alpha_;
   glow_scale_y_start_ = glow_scale_y_;

   edge_alpha_finish_ = 0.f;
   edge_scale_y_finish_ = 0.f;
   glow_alpha_finish_ = 0.f;
   glow_scale_y_finish_ = 0.f;

   start_time_ = current_time;
   duration_ = base::TimeDelta::FromMilliseconds(kRecedeTimeMs);
 }

 void EdgeEffect::Absorb(base::TimeTicks current_time, float velocity) {
   state_ = STATE_ABSORB;
   velocity = Clamp(std::abs(velocity), kMinVelocity, kMaxVelocity);

   start_time_ = current_time;
   // This should never be less than 1 millisecond.
   duration_ = base::TimeDelta::FromMilliseconds(0.15f + (velocity * 0.02f));

   // The edge should always be at least partially visible, regardless
   // of velocity.
   edge_alpha_start_ = 0.f;
   edge_scale_y_ = edge_scale_y_start_ = 0.f;
   // The glow depends more on the velocity, and therefore starts out
   // nearly invisible.
   glow_alpha_start_ = 0.3f;
   glow_scale_y_start_ = 0.f;

   // Factor the velocity by 8. Testing on device shows this works best to
   // reflect the strength of the user's scrolling.
   edge_alpha_finish_ = Clamp(velocity * kVelocityEdgeFactor, 0.f, 1.f);
   // Edge should never get larger than the size of its asset.
   edge_scale_y_finish_ =
       Clamp(velocity * kVelocityEdgeFactor, kHeldEdgeScaleY, 1.f);

   // Growth for the size of the glow should be quadratic to properly
   // respond
   // to a user's scrolling speed. The faster the scrolling speed, the more
   // intense the effect should be for both the size and the saturation.
   glow_scale_y_finish_ =
       std::min(0.025f + (velocity * (velocity / 100) * 0.00015f), 1.75f);
   // Alpha should change for the glow as well as size.
   glow_alpha_finish_ = Clamp(
       glow_alpha_start_, velocity * kVelocityGlowFactor * .00001f, kMaxAlpha);
 }

 bool EdgeEffect::Update(base::TimeTicks current_time) {
   if (IsFinished())
     return false;

   const double dt = (current_time - start_time_).InMilliseconds();
   const double t = std::min(dt / duration_.InMilliseconds(), 1.);
   const float interp = static_cast<float>(Damp(t, 1.));

   edge_alpha_ = Lerp(edge_alpha_start_, edge_alpha_finish_, interp);
   edge_scale_y_ = Lerp(edge_scale_y_start_, edge_scale_y_finish_, interp);
   glow_alpha_ = Lerp(glow_alpha_start_, glow_alpha_finish_, interp);
   glow_scale_y_ = Lerp(glow_scale_y_start_, glow_scale_y_finish_, interp);

   if (t >= 1.f - kEpsilon) {
     switch (state_) {
       case STATE_ABSORB:
         state_ = STATE_RECEDE;
         start_time_ = current_time;
         duration_ = base::TimeDelta::FromMilliseconds(kRecedeTimeMs);

         edge_alpha_start_ = edge_alpha_;
         edge_scale_y_start_ = edge_scale_y_;
         glow_alpha_start_ = glow_alpha_;
         glow_scale_y_start_ = glow_scale_y_;

         // After absorb, the glow and edge should fade to nothing.
         edge_alpha_finish_ = 0.f;
         edge_scale_y_finish_ = 0.f;
         glow_alpha_finish_ = 0.f;
         glow_scale_y_finish_ = 0.f;
         break;
       case STATE_PULL:
         state_ = STATE_PULL_DECAY;
         start_time_ = current_time;
         duration_ = base::TimeDelta::FromMilliseconds(kPullDecayTimeMs);

         edge_alpha_start_ = edge_alpha_;
         edge_scale_y_start_ = edge_scale_y_;
         glow_alpha_start_ = glow_alpha_;
         glow_scale_y_start_ = glow_scale_y_;

         // After pull, the glow and edge should fade to nothing.
         edge_alpha_finish_ = 0.f;
         edge_scale_y_finish_ = 0.f;
         glow_alpha_finish_ = 0.f;
         glow_scale_y_finish_ = 0.f;
         break;
       case STATE_PULL_DECAY: {
         // When receding, we want edge to decrease more slowly
         // than the glow.
         const float factor =
             glow_scale_y_finish_
                 ? 1 / (glow_scale_y_finish_ * glow_scale_y_finish_)
                 : std::numeric_limits<float>::max();
         edge_scale_y_ =
             edge_scale_y_start_ +
             (edge_scale_y_finish_ - edge_scale_y_start_) * interp * factor;
         state_ = STATE_RECEDE;
       } break;
       case STATE_RECEDE:
         Finish();
         break;
       default:
         break;
     }
   }

   if (state_ == STATE_RECEDE && glow_scale_y_ <= 0 && edge_scale_y_ <= 0)
     Finish();

   return !IsFinished();
 }

 float EdgeEffect::GetAlpha() const {
   return IsFinished() ? 0.f : std::max(glow_alpha_, edge_alpha_);
 }

 void EdgeEffect::ApplyToLayers(Edge edge,
                                const gfx::SizeF& viewport_size,
                                float offset) {
   if (IsFinished())
     return;

   // An empty window size, while meaningless, is also relatively harmless, and
   // will simply prevent any drawing of the layers.
   if (viewport_size.IsEmpty()) {
     edge_->Disable();
     glow_->Disable();
     return;
   }

   gfx::SizeF size = ComputeOrientedSize(edge, viewport_size);
   gfx::Transform transform = ComputeTransform(edge, viewport_size, offset);

   // Glow
   const int scaled_glow_height = static_cast<int>(
       std::min(base_glow_height_ * glow_scale_y_ * kGlowHeightWidthRatio * 0.6f,
                base_glow_height_ * kMaxGlowHeight) +
       0.5f);
   const gfx::Size glow_size(size.width(), scaled_glow_height);
   glow_->Update(glow_size, transform, glow_alpha_);

   // Edge
   const int scaled_edge_height =
       static_cast<int>(base_edge_height_ * edge_scale_y_);
   const gfx::Size edge_size(size.width(), scaled_edge_height);
   edge_->Update(edge_size, transform, edge_alpha_);
 }

 void EdgeEffect::SetParent(cc::Layer* parent) {
   edge_->SetParent(parent);
   glow_->SetParent(parent);
 }

 // static
 void EdgeEffect::PreloadResources(ui::ResourceManager* resource_manager) {
   DCHECK(resource_manager);
   resource_manager->PreloadResource(ui::ANDROID_RESOURCE_TYPE_SYSTEM,
                                     kEdgeResourceId);
   resource_manager->PreloadResource(ui::ANDROID_RESOURCE_TYPE_SYSTEM,
                                     kGlowResourceId);
 }

 }  // namespace ui
	// 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 "ui/android/edge_effect.h"

	#include "base/macros.h"
	#include "cc/layers/layer.h"
	#include "cc/layers/ui_resource_layer.h"
	#include "ui/android/animation_utils.h"
	#include "ui/android/resources/resource_manager.h"
	#include "ui/android/resources/system_ui_resource_type.h"
	#include "ui/android/window_android_compositor.h"

	namespace ui {

	namespace {

	const ui::SystemUIResourceType kEdgeResourceId = ui::OVERSCROLL_EDGE;
	const ui::SystemUIResourceType kGlowResourceId = ui::OVERSCROLL_GLOW;

	// Time it will take the effect to fully recede in ms
	const int kRecedeTimeMs = 1000;

	// Time it will take before a pulled glow begins receding in ms
	const int kPullTimeMs = 167;

	// Time it will take in ms for a pulled glow to decay before release
	const int kPullDecayTimeMs = 1000;

	const float kMaxAlpha = 1.f;
	const float kHeldEdgeScaleY = .5f;

	const float kMaxGlowHeight = 4.f;

	const float kPullGlowBegin = 1.f;
	const float kPullEdgeBegin = 0.6f;

	// Min/max velocity that will be absorbed
	const float kMinVelocity = 100.f;
	const float kMaxVelocity = 10000.f;

	const float kEpsilon = 0.001f;

	const float kGlowHeightWidthRatio = 0.25f;

	// How much dragging should effect the height of the edge image.
	// Number determined by user testing.
	const int kPullDistanceEdgeFactor = 7;

	// How much dragging should effect the height of the glow image.
	// Number determined by user testing.
	const int kPullDistanceGlowFactor = 7;
	const float kPullDistanceAlphaGlowFactor = 1.1f;

	const int kVelocityEdgeFactor = 8;
	const int kVelocityGlowFactor = 12;

	const float kEdgeHeightAtMdpi = 12.f;
	const float kGlowHeightAtMdpi = 128.f;

	} // namespace

	class EdgeEffect::EffectLayer {
	public:
	EffectLayer(ui::SystemUIResourceType resource_type,
	ui::ResourceManager* resource_manager)
	: ui_resource_layer_(cc::UIResourceLayer::Create()),
	resource_type_(resource_type),
	resource_manager_(resource_manager) {}

	~EffectLayer() { ui_resource_layer_->RemoveFromParent(); }

	void SetParent(cc::Layer* parent) {
	if (ui_resource_layer_->parent() != parent)
	parent->AddChild(ui_resource_layer_);
	}

	void Disable() { ui_resource_layer_->SetIsDrawable(false); }

	void Update(const gfx::Size& size,
	const gfx::Transform& transform,
	float opacity) {
	ui_resource_layer_->SetUIResourceId(resource_manager_->GetUIResourceId(
	ui::ANDROID_RESOURCE_TYPE_SYSTEM, resource_type_));
	ui_resource_layer_->SetIsDrawable(true);
	ui_resource_layer_->SetTransformOrigin(
	gfx::Point3F(size.width() * 0.5f, 0, 0));
	ui_resource_layer_->SetTransform(transform);
	ui_resource_layer_->SetBounds(size);
	ui_resource_layer_->SetOpacity(Clamp(opacity, 0.f, 1.f));
	}

	scoped_refptr<cc::UIResourceLayer> ui_resource_layer_;
	ui::SystemUIResourceType resource_type_;
	ui::ResourceManager* resource_manager_;

	DISALLOW_COPY_AND_ASSIGN(EffectLayer);
	};

	EdgeEffect::EdgeEffect(ui::ResourceManager* resource_manager,
	float device_scale_factor)
	: edge_(new EffectLayer(kEdgeResourceId, resource_manager)),
	glow_(new EffectLayer(kGlowResourceId, resource_manager)),
	base_edge_height_(kEdgeHeightAtMdpi * device_scale_factor),
	base_glow_height_(kGlowHeightAtMdpi * device_scale_factor),
	edge_alpha_(0),
	edge_scale_y_(0),
	glow_alpha_(0),
	glow_scale_y_(0),
	edge_alpha_start_(0),
	edge_alpha_finish_(0),
	edge_scale_y_start_(0),
	edge_scale_y_finish_(0),
	glow_alpha_start_(0),
	glow_alpha_finish_(0),
	glow_scale_y_start_(0),
	glow_scale_y_finish_(0),
	state_(STATE_IDLE),
	pull_distance_(0) {
	}

	EdgeEffect::~EdgeEffect() {
	}

	bool EdgeEffect::IsFinished() const {
	return state_ == STATE_IDLE;
	}

	void EdgeEffect::Finish() {
	edge_->Disable();
	glow_->Disable();
	pull_distance_ = 0;
	state_ = STATE_IDLE;
	}

	void EdgeEffect::Pull(base::TimeTicks current_time,
	float delta_distance,
	float displacement) {
	if (state_ == STATE_PULL_DECAY && current_time - start_time_ < duration_) {
	return;
	}
	if (state_ != STATE_PULL) {
	glow_scale_y_ = kPullGlowBegin;
	}
	state_ = STATE_PULL;

	start_time_ = current_time;
	duration_ = base::TimeDelta::FromMilliseconds(kPullTimeMs);

	float abs_delta_distance = std::abs(delta_distance);
	pull_distance_ += delta_distance;
	float distance = std::abs(pull_distance_);

	edge_alpha_ = edge_alpha_start_ = Clamp(distance, kPullEdgeBegin, kMaxAlpha);
	edge_scale_y_ = edge_scale_y_start_ =
	Clamp(distance * kPullDistanceEdgeFactor, kHeldEdgeScaleY, 1.f);

	glow_alpha_ = glow_alpha_start_ =
	std::min(kMaxAlpha,
	glow_alpha_ + abs_delta_distance * kPullDistanceAlphaGlowFactor);

	float glow_change = abs_delta_distance;
	if (delta_distance > 0 && pull_distance_ < 0)
	glow_change = -glow_change;
	if (pull_distance_ == 0)
	glow_scale_y_ = 0;

	// Do not allow glow to get larger than kMaxGlowHeight.
	glow_scale_y_ = glow_scale_y_start_ =
	Clamp(glow_scale_y_ + glow_change * kPullDistanceGlowFactor,
	0.f,
	kMaxGlowHeight);

	edge_alpha_finish_ = edge_alpha_;
	edge_scale_y_finish_ = edge_scale_y_;
	glow_alpha_finish_ = glow_alpha_;
	glow_scale_y_finish_ = glow_scale_y_;
	}

	void EdgeEffect::Release(base::TimeTicks current_time) {
	pull_distance_ = 0;

	if (state_ != STATE_PULL && state_ != STATE_PULL_DECAY)
	return;

	state_ = STATE_RECEDE;
	edge_alpha_start_ = edge_alpha_;
	edge_scale_y_start_ = edge_scale_y_;
	glow_alpha_start_ = glow_alpha_;
	glow_scale_y_start_ = glow_scale_y_;

	edge_alpha_finish_ = 0.f;
	edge_scale_y_finish_ = 0.f;
	glow_alpha_finish_ = 0.f;
	glow_scale_y_finish_ = 0.f;

	start_time_ = current_time;
	duration_ = base::TimeDelta::FromMilliseconds(kRecedeTimeMs);
	}

	void EdgeEffect::Absorb(base::TimeTicks current_time, float velocity) {
	state_ = STATE_ABSORB;
	velocity = Clamp(std::abs(velocity), kMinVelocity, kMaxVelocity);

	start_time_ = current_time;
	// This should never be less than 1 millisecond.
	duration_ = base::TimeDelta::FromMilliseconds(0.15f + (velocity * 0.02f));

	// The edge should always be at least partially visible, regardless
	// of velocity.
	edge_alpha_start_ = 0.f;
	edge_scale_y_ = edge_scale_y_start_ = 0.f;
	// The glow depends more on the velocity, and therefore starts out
	// nearly invisible.
	glow_alpha_start_ = 0.3f;
	glow_scale_y_start_ = 0.f;

	// Factor the velocity by 8. Testing on device shows this works best to
	// reflect the strength of the user's scrolling.
	edge_alpha_finish_ = Clamp(velocity * kVelocityEdgeFactor, 0.f, 1.f);
	// Edge should never get larger than the size of its asset.
	edge_scale_y_finish_ =
	Clamp(velocity * kVelocityEdgeFactor, kHeldEdgeScaleY, 1.f);

	// Growth for the size of the glow should be quadratic to properly
	// respond
	// to a user's scrolling speed. The faster the scrolling speed, the more
	// intense the effect should be for both the size and the saturation.
	glow_scale_y_finish_ =
	std::min(0.025f + (velocity * (velocity / 100) * 0.00015f), 1.75f);
	// Alpha should change for the glow as well as size.
	glow_alpha_finish_ = Clamp(
	glow_alpha_start_, velocity * kVelocityGlowFactor * .00001f, kMaxAlpha);
	}

	bool EdgeEffect::Update(base::TimeTicks current_time) {
	if (IsFinished())
	return false;

	const double dt = (current_time - start_time_).InMilliseconds();
	const double t = std::min(dt / duration_.InMilliseconds(), 1.);
	const float interp = static_cast<float>(Damp(t, 1.));

	edge_alpha_ = Lerp(edge_alpha_start_, edge_alpha_finish_, interp);
	edge_scale_y_ = Lerp(edge_scale_y_start_, edge_scale_y_finish_, interp);
	glow_alpha_ = Lerp(glow_alpha_start_, glow_alpha_finish_, interp);
	glow_scale_y_ = Lerp(glow_scale_y_start_, glow_scale_y_finish_, interp);

	if (t >= 1.f - kEpsilon) {
	switch (state_) {
	case STATE_ABSORB:
	state_ = STATE_RECEDE;
	start_time_ = current_time;
	duration_ = base::TimeDelta::FromMilliseconds(kRecedeTimeMs);

	edge_alpha_start_ = edge_alpha_;
	edge_scale_y_start_ = edge_scale_y_;
	glow_alpha_start_ = glow_alpha_;
	glow_scale_y_start_ = glow_scale_y_;

	// After absorb, the glow and edge should fade to nothing.
	edge_alpha_finish_ = 0.f;
	edge_scale_y_finish_ = 0.f;
	glow_alpha_finish_ = 0.f;
	glow_scale_y_finish_ = 0.f;
	break;
	case STATE_PULL:
	state_ = STATE_PULL_DECAY;
	start_time_ = current_time;
	duration_ = base::TimeDelta::FromMilliseconds(kPullDecayTimeMs);

	edge_alpha_start_ = edge_alpha_;
	edge_scale_y_start_ = edge_scale_y_;
	glow_alpha_start_ = glow_alpha_;
	glow_scale_y_start_ = glow_scale_y_;

	// After pull, the glow and edge should fade to nothing.
	edge_alpha_finish_ = 0.f;
	edge_scale_y_finish_ = 0.f;
	glow_alpha_finish_ = 0.f;
	glow_scale_y_finish_ = 0.f;
	break;
	case STATE_PULL_DECAY: {
	// When receding, we want edge to decrease more slowly
	// than the glow.
	const float factor =
	glow_scale_y_finish_
	? 1 / (glow_scale_y_finish_ * glow_scale_y_finish_)
	: std::numeric_limits<float>::max();
	edge_scale_y_ =
	edge_scale_y_start_ +
	(edge_scale_y_finish_ - edge_scale_y_start_) * interp * factor;
	state_ = STATE_RECEDE;
	} break;
	case STATE_RECEDE:
	Finish();
	break;
	default:
	break;
	}
	}

	if (state_ == STATE_RECEDE && glow_scale_y_ <= 0 && edge_scale_y_ <= 0)
	Finish();

	return !IsFinished();
	}

	float EdgeEffect::GetAlpha() const {
	return IsFinished() ? 0.f : std::max(glow_alpha_, edge_alpha_);
	}

	void EdgeEffect::ApplyToLayers(Edge edge,
	const gfx::SizeF& viewport_size,
	float offset) {
	if (IsFinished())
	return;

	// An empty window size, while meaningless, is also relatively harmless, and
	// will simply prevent any drawing of the layers.
	if (viewport_size.IsEmpty()) {
	edge_->Disable();
	glow_->Disable();
	return;
	}

	gfx::SizeF size = ComputeOrientedSize(edge, viewport_size);
	gfx::Transform transform = ComputeTransform(edge, viewport_size, offset);

	// Glow
	const int scaled_glow_height = static_cast<int>(
	std::min(base_glow_height_ * glow_scale_y_ * kGlowHeightWidthRatio * 0.6f,
	base_glow_height_ * kMaxGlowHeight) +
	0.5f);
	const gfx::Size glow_size(size.width(), scaled_glow_height);
	glow_->Update(glow_size, transform, glow_alpha_);

	// Edge
	const int scaled_edge_height =
	static_cast<int>(base_edge_height_ * edge_scale_y_);
	const gfx::Size edge_size(size.width(), scaled_edge_height);
	edge_->Update(edge_size, transform, edge_alpha_);
	}

	void EdgeEffect::SetParent(cc::Layer* parent) {
	edge_->SetParent(parent);
	glow_->SetParent(parent);
	}

	// static
	void EdgeEffect::PreloadResources(ui::ResourceManager* resource_manager) {
	DCHECK(resource_manager);
	resource_manager->PreloadResource(ui::ANDROID_RESOURCE_TYPE_SYSTEM,
	kEdgeResourceId);
	resource_manager->PreloadResource(ui::ANDROID_RESOURCE_TYPE_SYSTEM,
	kGlowResourceId);
	}

	} // namespace ui