Implement initial version of scroll end effect

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

 // Copyright 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 "chrome/browser/ui/views/frame/scroll_end_effect_controller_ash.h"
 
-ScrollEndEffectController* ScrollEndEffectController::Create() {
-  return new ScrollEndEffectControllerAsh();
-}
-
-ScrollEndEffectControllerAsh::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 "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/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 = 0.05;
+}
+
+// To achieve the desired effect to indicate vertical overscroll is occuring the
+// layer tree needs to be manipulated. Specifically two clipping layers are
+// inserted and the parenting of the web contents and non-client layers are
+// modified. These modifications are removed when the effect is deactivated.
+//
+// The |frame_clipping_layer_| is used to make sure that the bits of the layers
+// below do not peak out since the |browser_frame_layer| is going to be scaled
+// down in size, but some of the sub-layers are going to be counter scaled. This
+// clipping cannot be done in the |browser_frame_layer| since the shadows on the
+// window are outside the clipping bounds, but also children of that layer.
+//
+// The |web_clipping_layer_| is used to trim the web contents so that is does
+// not occlude the non-client elements. This is done to give the visual effect
+// of the contents slide under the top elements without having to break these
+// elements out into their own layer.
+//
+// Additionally the layer associated with the dev tools is promoted, so that it
+// isn't occuluded by the web contents layer.
+//
+// Layout of layer tree when effect is not active:
+//  +----------------------------------------------------------+
+//  |                    browser_frame_layer                   |
+//  +-+--------------+---------------+-----------------------+-+
+//    |              |               |                       |
+//    |              v               v                       v
+//    v    +-------------------+  +---------------------+  +-----------------+
+//   ...   | non_client_layer_ |  | web_contents_layer_ |  | devtools_layer_ |
+//         +-------------------+  +---------------------+  +-----------------+
+//
+//
+// Layout of the layer tree when effect is active:
+//  +---------------------+
+//  | browser_frame_layer |
+//  +-+---------------+---+
+//    |               |
+//    |               v
+//    v        +-------------------------------------------------+
+//   ...       |              frame_clipping_layer_              |
+//             +-----+--------------+---------------------+------+
+//                   |              |                     |
+//                   v              v                     V
+//     +-------------------+  +---------------------+  +-----------------+
+//     | non_client_layer_ |  | web_clipping_layer_ |  | devtools_layer_ |
+//     +-------------------+  +---------+-----------+  +-----------------+
+//                                      |
+//                                      v
+//                            +---------------------+
+//                            | web_contents_layer_ |

[Ian Vollick, 2013/09/04 16:41:09]

Nice diagram!

[rharrison, 2013/09/04 17:41:17]

thanks

+//                            +---------------------+
+
+ScrollEndEffectController* ScrollEndEffectController::Create(
+    ScrollEndEffectControllerDelegate* delegate) {
+  return new ScrollEndEffectControllerAsh(delegate);
+}
+
+ScrollEndEffectControllerAsh::ScrollEndEffectControllerAsh(
+    ScrollEndEffectControllerDelegate* delegate)
+    : delegate_(delegate),
+      is_effect_active_(false),
+      non_client_layer_(NULL),
+      web_contents_layer_(NULL),
+      devtools_layer_(NULL),
+      web_contents_parent_(NULL),
+      devtools_parent_(NULL),
+      non_client_view_(NULL) {
 }
 
 ScrollEndEffectControllerAsh::~ScrollEndEffectControllerAsh() {
 }
 
 void ScrollEndEffectControllerAsh::OverscrollUpdate(int delta_y) {
-  // TODO(rharrison): Implement initial version of scroll end effect
-}
+  if (delegate_ == NULL) {
+    return;

[Ian Vollick, 2013/09/04 16:41:09]

nit: no braces.

[rharrison, 2013/09/04 17:41:17]

Done.

+  }
+
+  ui::Layer* browser_frame_layer = delegate_->GetBrowserFrameLayer();
+  if (!browser_frame_layer)
+    return;
+
+  if (delta_y == 0 && is_effect_active_) {
+    ApplyDelta(0);
+    DeactivateEffect();
+    return;
+  }
+
+  if (!is_effect_active_)
+    ActivateEffect();
+
+  int capped_delta_y = delta_y;
+  gfx::Rect bounds = browser_frame_layer->bounds();
+  // Limiting the delta size being a proportion of the frame bounds size.
+  if (capped_delta_y > 0) {
+    capped_delta_y = std::min(gfx::ToRoundedInt((bounds.height() *
+                                                 kScrollEndEffectFactor)),
+                              capped_delta_y);
+  } else if (capped_delta_y < 0) {
+    capped_delta_y = -std::min(gfx::ToRoundedInt((bounds.height() *
+                                                  kScrollEndEffectFactor)),
+                               -capped_delta_y);
+  }
+  ApplyDelta(capped_delta_y);
+}
+
+void ScrollEndEffectControllerAsh::ActivateEffect() {
+  ui::Layer* browser_frame_layer = delegate_->GetBrowserFrameLayer();
+  if (!browser_frame_layer)
+    return;
+
+  is_effect_active_ = true;
+
+  // Get layers for all of the parts to be manipulated
+  non_client_view_ = delegate_->GetNonClientView();
+  non_client_layer_ = CreateViewLayer(non_client_view_);
+  web_contents_layer_ = delegate_->GetWebContentsLayer();
+  devtools_layer_ = delegate_->GetDevToolsLayer();
+  download_view_ = delegate_->GetDownloadView();
+  download_layer_ = CreateViewLayer(download_view_);
+
+  CHECK(non_client_layer_);
+  CHECK(web_contents_layer_);
+  CHECK(devtools_layer_);
+  CHECK(download_layer_);
+
+  frame_clipping_layer_.reset(CreateClippingLayer(
+      "OverscrollFrameClippingLayer"));
+  web_clipping_layer_.reset(CreateClippingLayer("OverscrollWebClippingLayer"));
+
+  // Save bounds for restoring later
+  devtools_bounds_ = devtools_layer_->bounds();
+  web_contents_bounds_ = web_contents_layer_->bounds();
+
+  // Adjust the toplogy of the layer tree to add clipping layers
+  devtools_parent_ = devtools_layer_->parent();
+  web_contents_parent_ = web_contents_layer_->parent();
+  browser_frame_layer->Add(frame_clipping_layer_.get());
+  frame_clipping_layer_->Add(non_client_layer_);
+  frame_clipping_layer_->Add(web_clipping_layer_.get());
+  frame_clipping_layer_->Add(devtools_layer_);
+  frame_clipping_layer_->Add(download_layer_);
+  web_clipping_layer_->Add(web_contents_layer_);
+}
+
+ui::Layer* ScrollEndEffectControllerAsh::CreateClippingLayer(std::string name) {
+  ui::Layer* layer = new ui::Layer(ui::LAYER_NOT_DRAWN);
+  layer->set_name(name);
+  layer->SetMasksToBounds(true);
+  layer->SetFillsBoundsOpaquely(false);
+  return layer;
+}
+
+ui::Layer* ScrollEndEffectControllerAsh::CreateViewLayer(views::View* view) {
+  view->SetPaintToLayer(true);
+  ui::Layer* layer = view->layer();
+  layer->SetFillsBoundsOpaquely(false);
+  return layer;
+}
+
+void ScrollEndEffectControllerAsh::DeactivateEffect() {
+  ui::Layer* browser_frame_layer = delegate_->GetBrowserFrameLayer();
+  if (!browser_frame_layer)
+    return;
+
+  is_effect_active_ = false;
+
+  devtools_layer_->SetBounds(devtools_bounds_);
+  devtools_parent_->Add(devtools_layer_);
+  devtools_parent_ = NULL;
+  devtools_layer_ = NULL;
+
+  web_contents_layer_->SetBounds(web_contents_bounds_);
+  web_contents_parent_->Add(web_contents_layer_);
+  web_contents_parent_ = NULL;
+  web_contents_layer_ = NULL;
+
+  frame_clipping_layer_->Remove(download_layer_);
+  download_view_->SetPaintToLayer(false);
+  download_layer_ = NULL;
+  download_view_ = NULL;
+
+  frame_clipping_layer_->Remove(non_client_layer_);
+  non_client_view_->SetPaintToLayer(false);
+  non_client_layer_ = NULL;
+  non_client_view_ = NULL;
+
+  frame_clipping_layer_->Remove(web_clipping_layer_.get());
+  web_clipping_layer_.reset();
+  browser_frame_layer->Remove(frame_clipping_layer_.get());
+  frame_clipping_layer_.reset();
+  browser_frame_layer = NULL;
+}
+
+void ScrollEndEffectControllerAsh::ApplyDelta(int delta_y) {
+  SetBoundsForEffect();
+
+  ui::Layer* frame = delegate_->GetBrowserFrameLayer();
+  gfx::Rect bounds = frame->bounds();
+
+  float scale_factor = std::abs(delta_y);
+  scale_factor /= bounds.height();
+  scale_factor = 1 - scale_factor;
+
+  gfx::Transform frame_transform;
+  if (delta_y > 0) {
+    frame_transform.Translate(0, delta_y);
+    frame_transform.Scale(1, scale_factor);
+  } else {
+    frame_transform.Scale(1, scale_factor);
+  }
+  CHECK(frame_transform.GetInverse(&counter_transform_));
+  frame->SetTransform(frame_transform);
+
+  gfx::Transform download_transform =
+      CounterTransfromAboutPoint(0,
+                                 download_layer_->bounds().origin().y());
+  if (delta_y < 0)
+    download_transform.Translate(0, delta_y);
+  download_layer_->SetTransform(download_transform);
+
+  gfx::Transform devtools_transform =
+      CounterTransfromAboutPoint(0,
+                                 devtools_layer_->bounds().origin().y());
+  if (delta_y < 0)
+    devtools_transform.Translate(0, delta_y);
+  devtools_layer_->SetTransform(devtools_transform);
+
+  gfx::Transform web_clipping_transform =
+      CounterTransfromAboutPoint(0,
+                                 web_clipping_layer_->bounds().origin().y());
+  if (delta_y >= 0)
+    web_clipping_transform.Translate(0, delta_y);
+  web_clipping_layer_->SetTransform(web_clipping_transform);
+
+  if (delta_y <= 0) {
+    gfx::Transform web_contents_transform;
+    web_contents_transform.Translate(0, delta_y);
+    web_contents_layer_->SetTransform(web_contents_transform);
+  }
+
+  gfx::Transform non_client_transform = counter_transform_;
+  if (delta_y >= 0)
+    non_client_transform.Translate(0, delta_y);
+  non_client_layer_->SetTransform(non_client_transform);
+}
+
+void ScrollEndEffectControllerAsh::SetBoundsForEffect() {
+  ui::Layer* browser_frame_layer = delegate_->GetBrowserFrameLayer();
+  if (!browser_frame_layer)
+    return;
+
+  gfx::Rect frame_clipping_bounds = browser_frame_layer->bounds();
+  frame_clipping_bounds.set_origin(gfx::Point());
+  frame_clipping_layer_->SetBounds(frame_clipping_bounds);
+
+  gfx::Rect web_clipping_bounds = browser_frame_layer->bounds();
+  int download_height = download_view_->visible() ?
+      download_view_->bounds().height() : 0;
+  int non_client_top_height = browser_frame_layer->bounds().height() -
+      web_contents_layer_->bounds().height() -
+      delegate_->GetDevToolsHeight() -
+      delegate_->GetDividerHeight() -
+      download_height;
+  int web_clipping_height = browser_frame_layer->bounds().height() -
+      non_client_top_height -
+      delegate_->GetDevToolsHeight() -
+      delegate_->GetDividerHeight() -
+      download_height;
+
+  web_clipping_bounds.set_height(web_clipping_height);
+  web_clipping_bounds.set_origin(gfx::Point(0, non_client_top_height));
+  web_clipping_layer_->SetBounds(web_clipping_bounds);
+
+  gfx::Rect devtools_bounds = browser_frame_layer->bounds();
+  devtools_bounds.set_origin(gfx::Point(0,
+                                        browser_frame_layer->bounds().height() -
+                                        delegate_->GetDevToolsHeight() -
+                                        download_height));
+  devtools_bounds.set_height(delegate_->GetDevToolsHeight());
+  devtools_layer_->SetBounds(devtools_bounds);
+
+  // Move the web contents since bounds are relative to the parent layer
+  gfx::Rect web_contents_bounds = web_clipping_bounds;
+  web_contents_bounds.set_origin(gfx::Point(0, 0));
+  web_contents_layer_->SetBounds(web_contents_bounds);
+}
+
+gfx::Transform ScrollEndEffectControllerAsh::CounterTransfromAboutPoint(int x,
+                                                                        int y) {
+  gfx::Transform to_frame_transform;
+  to_frame_transform.Translate(-x, -y);
+  gfx::Transform from_frame_transform;
+  from_frame_transform.Translate(x, y);
+  gfx::Transform transform = counter_transform_;
+  transform.ConcatTransform(to_frame_transform);
+  transform.PreconcatTransform(from_frame_transform);
+  return transform;
+}