content/browser/android/overscroll_glow.cc

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "content/browser/android/overscroll_glow.h"
   6
   7 #include "cc/layers/layer.h"
   8 #include "content/browser/android/edge_effect_base.h"
   9
  10 using std::max;
  11 using std::min;
  12
  13 namespace content {
  14
  15 namespace {
  16
  17 const float kEpsilon = 1e-3f;
  18
  19 bool IsApproxZero(float value) {
  20   return std::abs(value) < kEpsilon;
  21 }
  22
  23 gfx::Vector2dF ZeroSmallComponents(gfx::Vector2dF vector) {
  24   if (IsApproxZero(vector.x()))
  25     vector.set_x(0);
  26   if (IsApproxZero(vector.y()))
  27     vector.set_y(0);
  28   return vector;
  29 }
  30
  31 gfx::Transform ComputeTransform(OverscrollGlow::Edge edge,
  32                                 const gfx::SizeF& window_size,
  33                                 float offset) {
  34   // Transforms assume the edge layers are anchored to their *top center point*.
  35   switch (edge) {
  36     case OverscrollGlow::EDGE_TOP:
  37       return gfx::Transform(1, 0, 0, 1, 0, offset);
  38     case OverscrollGlow::EDGE_LEFT:
  39       return gfx::Transform(0,
  40                             1,
  41                             -1,
  42                             0,
  43                             -window_size.height() / 2.f + offset,
  44                             window_size.height() / 2.f);
  45     case OverscrollGlow::EDGE_BOTTOM:
  46       return gfx::Transform(-1, 0, 0, -1, 0, window_size.height() + offset);
  47     case OverscrollGlow::EDGE_RIGHT:
  48       return gfx::Transform(
  49           0,
  50           -1,
  51           1,
  52           0,
  53           -window_size.height() / 2.f + window_size.width() + offset,
  54           window_size.height() / 2.f);
  55     default:
  56       NOTREACHED() << "Invalid edge: " << edge;
  57       return gfx::Transform();
  58   };
  59 }
  60
  61 gfx::SizeF ComputeSize(OverscrollGlow::Edge edge,
  62                        const gfx::SizeF& window_size) {
  63   switch (edge) {
  64     case OverscrollGlow::EDGE_TOP:
  65     case OverscrollGlow::EDGE_BOTTOM:
  66       return window_size;
  67     case OverscrollGlow::EDGE_LEFT:
  68     case OverscrollGlow::EDGE_RIGHT:
  69       return gfx::SizeF(window_size.height(), window_size.width());
  70     default:
  71       NOTREACHED() << "Invalid edge: " << edge;
  72       return gfx::SizeF();
  73   };
  74 }
  75
  76 }  // namespace
  77
  78 OverscrollGlow::OverscrollGlow(OverscrollGlowClient* client)
  79     : client_(client), edge_offsets_(), initialized_(false) {
  80   DCHECK(client);
  81 }
  82
  83 OverscrollGlow::~OverscrollGlow() {
  84   Detach();
  85 }
  86
  87 void OverscrollGlow::Reset() {
  88   if (!initialized_)
  89     return;
  90   Detach();
  91   for (size_t i = 0; i < EDGE_COUNT; ++i)
  92     edge_effects_[i]->Finish();
  93 }
  94
  95 bool OverscrollGlow::IsActive() const {
  96   if (!initialized_)
  97     return false;
  98   for (size_t i = 0; i < EDGE_COUNT; ++i) {
  99     if (!edge_effects_[i]->IsFinished())
 100       return true;
 101   }
 102   return false;
 103 }
 104
 105 float OverscrollGlow::GetVisibleAlpha() const {
 106   float max_alpha = 0;
 107   for (size_t i = 0; i < EDGE_COUNT; ++i) {
 108     if (!edge_effects_[i]->IsFinished())
 109       max_alpha = std::max(max_alpha, edge_effects_[i]->GetAlpha());
 110   }
 111   return std::min(max_alpha, 1.f);
 112 }
 113
 114 bool OverscrollGlow::OnOverscrolled(base::TimeTicks current_time,
 115           const gfx::Vector2dF& accumulated_overscroll,
 116           gfx::Vector2dF overscroll_delta,
 117           gfx::Vector2dF velocity,
 118           const gfx::Vector2dF& displacement) {
 119   // The size of the glow determines the relative effect of the inputs; an
 120   // empty-sized effect is effectively disabled.
 121   if (viewport_size_.IsEmpty())
 122     return false;
 123
 124   // Ignore sufficiently small values that won't meaningfuly affect animation.
 125   overscroll_delta = ZeroSmallComponents(overscroll_delta);
 126   if (overscroll_delta.IsZero()) {
 127     if (initialized_)
 128       Release(current_time);
 129     return CheckNeedsAnimate();
 130   }
 131
 132   if (!InitializeIfNecessary())
 133     return false;
 134
 135   gfx::Vector2dF old_overscroll = accumulated_overscroll - overscroll_delta;
 136   bool x_overscroll_started =
 137       !IsApproxZero(overscroll_delta.x()) && IsApproxZero(old_overscroll.x());
 138   bool y_overscroll_started =
 139       !IsApproxZero(overscroll_delta.y()) && IsApproxZero(old_overscroll.y());
 140
 141   velocity = ZeroSmallComponents(velocity);
 142   if (!velocity.IsZero())
 143     Absorb(current_time, velocity, x_overscroll_started, y_overscroll_started);
 144   else
 145     Pull(current_time, overscroll_delta, displacement);
 146
 147   return CheckNeedsAnimate();
 148 }
 149
 150 bool OverscrollGlow::Animate(base::TimeTicks current_time,
 151                              cc::Layer* parent_layer) {
 152   DCHECK(parent_layer);
 153   if (!CheckNeedsAnimate())
 154     return false;
 155
 156   UpdateLayerAttachment(parent_layer);
 157
 158   for (size_t i = 0; i < EDGE_COUNT; ++i) {
 159     if (edge_effects_[i]->Update(current_time)) {
 160       Edge edge = static_cast<Edge>(i);
 161       edge_effects_[i]->ApplyToLayers(
 162           ComputeSize(edge, viewport_size_),
 163           ComputeTransform(edge, viewport_size_, edge_offsets_[i]));
 164     }
 165   }
 166
 167   return CheckNeedsAnimate();
 168 }
 169
 170 void OverscrollGlow::OnFrameUpdated(
 171     const gfx::SizeF& viewport_size,
 172     const gfx::SizeF& content_size,
 173     const gfx::Vector2dF& content_scroll_offset) {
 174   viewport_size_ = viewport_size;
 175   edge_offsets_[OverscrollGlow::EDGE_TOP] = -content_scroll_offset.y();
 176   edge_offsets_[OverscrollGlow::EDGE_LEFT] = -content_scroll_offset.x();
 177   edge_offsets_[OverscrollGlow::EDGE_BOTTOM] = content_size.height() -
 178                                                content_scroll_offset.y() -
 179                                                viewport_size.height();
 180   edge_offsets_[OverscrollGlow::EDGE_RIGHT] =
 181       content_size.width() - content_scroll_offset.x() - viewport_size.width();
 182 }
 183
 184 bool OverscrollGlow::CheckNeedsAnimate() {
 185   if (!initialized_) {
 186     Detach();
 187     return false;
 188   }
 189
 190   if (IsActive())
 191     return true;
 192
 193   Detach();
 194   return false;
 195 }
 196
 197 void OverscrollGlow::UpdateLayerAttachment(cc::Layer* parent) {
 198   DCHECK(parent);
 199   if (!root_layer_.get())
 200     return;
 201
 202   if (!CheckNeedsAnimate())
 203     return;
 204
 205   if (root_layer_->parent() != parent)
 206     parent->AddChild(root_layer_);
 207
 208   for (size_t i = 0; i < EDGE_COUNT; ++i)
 209     edge_effects_[i]->SetParent(root_layer_.get());
 210 }
 211
 212 void OverscrollGlow::Detach() {
 213   if (root_layer_.get())
 214     root_layer_->RemoveFromParent();
 215 }
 216
 217 bool OverscrollGlow::InitializeIfNecessary() {
 218   if (initialized_)
 219     return true;
 220
 221   DCHECK(!root_layer_.get());
 222   root_layer_ = cc::Layer::Create();
 223   for (size_t i = 0; i < EDGE_COUNT; ++i) {
 224     edge_effects_[i] = client_->CreateEdgeEffect();
 225     DCHECK(edge_effects_[i]);
 226   }
 227
 228   initialized_ = true;
 229   return true;
 230 }
 231
 232 void OverscrollGlow::Pull(base::TimeTicks current_time,
 233                           const gfx::Vector2dF& overscroll_delta,
 234                           const gfx::Vector2dF& overscroll_location) {
 235   DCHECK(initialized_);
 236   DCHECK(!overscroll_delta.IsZero());
 237   DCHECK(!viewport_size_.IsEmpty());
 238   const float inv_width = 1.f / viewport_size_.width();
 239   const float inv_height = 1.f / viewport_size_.height();
 240
 241   gfx::Vector2dF overscroll_pull =
 242       gfx::ScaleVector2d(overscroll_delta, inv_width, inv_height);
 243   const float edge_pull[EDGE_COUNT] = {
 244       min(overscroll_pull.y(), 0.f),  // Top
 245       min(overscroll_pull.x(), 0.f),  // Left
 246       max(overscroll_pull.y(), 0.f),  // Bottom
 247       max(overscroll_pull.x(), 0.f)   // Right
 248   };
 249
 250   gfx::Vector2dF displacement =
 251       gfx::ScaleVector2d(overscroll_location, inv_width, inv_height);
 252   displacement.set_x(max(0.f, min(1.f, displacement.x())));
 253   displacement.set_y(max(0.f, min(1.f, displacement.y())));
 254   const float edge_displacement[EDGE_COUNT] = {
 255       1.f - displacement.x(),  // Top
 256       displacement.y(),        // Left
 257       displacement.x(),        // Bottom
 258       1.f - displacement.y()   // Right
 259   };
 260
 261   for (size_t i = 0; i < EDGE_COUNT; ++i) {
 262     if (!edge_pull[i])
 263       continue;
 264
 265     edge_effects_[i]->Pull(
 266         current_time, std::abs(edge_pull[i]), edge_displacement[i]);
 267     GetOppositeEdge(i)->Release(current_time);
 268   }
 269 }
 270
 271 void OverscrollGlow::Absorb(base::TimeTicks current_time,
 272                             const gfx::Vector2dF& velocity,
 273                             bool x_overscroll_started,
 274                             bool y_overscroll_started) {
 275   DCHECK(initialized_);
 276   DCHECK(!velocity.IsZero());
 277
 278   // Only trigger on initial overscroll at a non-zero velocity
 279   const float overscroll_velocities[EDGE_COUNT] = {
 280       y_overscroll_started ? min(velocity.y(), 0.f) : 0,  // Top
 281       x_overscroll_started ? min(velocity.x(), 0.f) : 0,  // Left
 282       y_overscroll_started ? max(velocity.y(), 0.f) : 0,  // Bottom
 283       x_overscroll_started ? max(velocity.x(), 0.f) : 0   // Right
 284   };
 285
 286   for (size_t i = 0; i < EDGE_COUNT; ++i) {
 287     if (!overscroll_velocities[i])
 288       continue;
 289
 290     edge_effects_[i]->Absorb(current_time, std::abs(overscroll_velocities[i]));
 291     GetOppositeEdge(i)->Release(current_time);
 292   }
 293 }
 294
 295 void OverscrollGlow::Release(base::TimeTicks current_time) {
 296   DCHECK(initialized_);
 297   for (size_t i = 0; i < EDGE_COUNT; ++i)
 298     edge_effects_[i]->Release(current_time);
 299 }
 300
 301 EdgeEffectBase* OverscrollGlow::GetOppositeEdge(int edge_index) {
 302   DCHECK(initialized_);
 303   return edge_effects_[(edge_index + 2) % EDGE_COUNT].get();
 304 }
 305
 306 }  // namespace content