Implement initial version of scroll end effect

chrome/browser/ui/views/frame/scroll_end_effect_controller_ash.cc

Index: chrome/browser/ui/views/frame/scroll_end_effect_controller_ash.cc
diff --git a/chrome/browser/ui/views/frame/scroll_end_effect_controller_ash.cc b/chrome/browser/ui/views/frame/scroll_end_effect_controller_ash.cc
index aa0642821e61bc5cfe4d5932bf978aca44f60377..fcb8f964e6107fa225809ba8f773ad8a90ee0b2e 100644
--- a/chrome/browser/ui/views/frame/scroll_end_effect_controller_ash.cc
+++ b/chrome/browser/ui/views/frame/scroll_end_effect_controller_ash.cc
@@ -4,16 +4,122 @@
 
 #include "chrome/browser/ui/views/frame/scroll_end_effect_controller_ash.h"
 
-ScrollEndEffectController* ScrollEndEffectController::Create() {
-  return new ScrollEndEffectControllerAsh();
+#include "chrome/browser/ui/views/download/download_shelf_view.h"
+#include "chrome/browser/ui/views/frame/browser_frame.h"
+#include "chrome/browser/ui/views/frame/browser_view.h"
+#include "chrome/browser/ui/views/frame/contents_container.h"
+#include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_view.h"
+#include "ui/aura/window.h"
+#include "ui/compositor/layer_type.h"
+#include "ui/gfx/animation/tween.h"
+#include "ui/gfx/rect_conversions.h"
+#include "ui/gfx/safe_integer_conversions.h"
+#include "ui/views/controls/single_split_view.h"
+#include "ui/views/controls/webview/webview.h"
+
+namespace {
+// This factor is used to control how much translation is applied relative to
+// the size of the window. Specifically translation is limited to a max of
+// window_size * factor.
+const float kScrollEndEffectFactor = 0.05f;
+}  // namespace
+
+ScrollEndEffectController* ScrollEndEffectController::Create(
+    ScrollEndEffectControllerDelegate* delegate) {
+  return new ScrollEndEffectControllerAsh(delegate);
 }
 
-ScrollEndEffectControllerAsh::ScrollEndEffectControllerAsh() {
+ScrollEndEffectControllerAsh::ScrollEndEffectControllerAsh(
+    ScrollEndEffectControllerDelegate* delegate)
+    : delegate_(delegate),
+      is_effect_active_(false),
+      start_delta_y_(0),
+      current_delta_y_(0),
+      end_delta_y_(0) {
+  animation_.reset(new gfx::SlideAnimation(this));
+  animation_->SetSlideDuration(100);
+  animation_->SetTweenType(gfx::Tween::EASE_OUT);
 }
 
 ScrollEndEffectControllerAsh::~ScrollEndEffectControllerAsh() {
 }
 
 void ScrollEndEffectControllerAsh::OverscrollUpdate(int delta_y) {
-  // TODO(rharrison): Implement initial version of scroll end effect
+  if (!is_effect_active_ && delta_y == 0)
+    return;
+
+  if (!is_effect_active_)
+    ActivateEffect();
+
+  int capped_delta_y = delta_y;
+  // Limiting the delta size being a proportion of the frame bounds size.
+  if (capped_delta_y > 0) {
+    capped_delta_y = std::min(gfx::ToRoundedInt((frame_bounds_.height() *
+                                                 kScrollEndEffectFactor)),
+                              capped_delta_y);
+  } else if (capped_delta_y < 0) {
+    capped_delta_y = -std::min(gfx::ToRoundedInt((frame_bounds_.height() *
+                                                  kScrollEndEffectFactor)),
+                               -capped_delta_y);
+  }
+
+  start_delta_y_ = current_delta_y_;
+  end_delta_y_ = capped_delta_y;
+  if (end_delta_y_ == 0) {
+    animation_->Reset();
+    animation_->Show();
+    if (animation_->GetSlideDuration() == 0) {
+      AnimationProgressed(animation_.get());
+      AnimationEnded(animation_.get());
+    }
+  } else {
+    animation_->Reset();
+    ApplyDelta(end_delta_y_);
+  }
+}
+
+void ScrollEndEffectControllerAsh::AnimationEnded(
+    const gfx::Animation* animation) {
+  if (current_delta_y_ == 0)
+    DeactivateEffect();
+}
+
+void ScrollEndEffectControllerAsh::AnimationProgressed(
+    const gfx::Animation* animation) {
+  ApplyDelta(gfx::Tween::IntValueBetween(animation_->GetCurrentValue(),
+                                         start_delta_y_,
+                                         end_delta_y_));
+}
+
+void ScrollEndEffectControllerAsh::ActivateEffect() {
+  is_effect_active_ = true;
+  frame_bounds_ = delegate_->GetFrameBounds();
+  delegate_->GetContentsContainer()->ActivateScrollEndEffect();
+}
+
+void ScrollEndEffectControllerAsh::DeactivateEffect() {
+  is_effect_active_ = false;
+  delegate_->SetFrameBounds(frame_bounds_);
+  delegate_->GetContentsContainer()->DeactivateScrollEndEffect();
+}
+
+void ScrollEndEffectControllerAsh::ApplyDelta(int delta_y) {
+  current_delta_y_ = delta_y;
+  gfx::Rect bounds = frame_bounds_;
+
+  float scale_factor = 1.0f - static_cast<float>(std::abs(current_delta_y_)) /
+      static_cast<float>(bounds.height());
+
+  bounds.set_height(gfx::ToRoundedInt(bounds.height() * scale_factor));
+  bool scrolling_down = current_delta_y_ > 0;
+  if (scrolling_down) {
+    gfx::Point bounds_orig = bounds.origin();
+    bounds_orig.set_y(bounds_orig.y() + current_delta_y_);
+    bounds.set_origin(bounds_orig);
+  }
+  delegate_->SetFrameBounds(bounds);
+  delegate_->GetContentsContainer()->
+      UpdateScrollEndEffectHeightDelta(frame_bounds_.height() - bounds.height(),
+                                       scrolling_down);
 }