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/base/animation/tween.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;
+
+// Utility methods used to create needed layers.
+ui::Layer* CreateClippingLayer(const 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* CreateViewLayer(views::View* view) {
+  view->SetPaintToLayer(true);
+  ui::Layer* layer = view->layer();
+  layer->SetFillsBoundsOpaquely(false);
+  view->parent()->SchedulePaint();

[sky, 2013/09/05 21:12:57]

Why do you need the SchedulePaint here?

[rharrison, 2013/09/09 20:01:17]

Without it there is a stale version of the parent with the view still in it,
since nothing else is scheduling a paint for it while the effect is running.
When using a translucent frame this causes the what looks like a double paint at
the top of the window, one version being scaled.

+  return layer;
+}
+
+}  // namespace
+
+// 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 |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 |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:
+//  +----------------------------------------------------------+
+//  |                        frame_layer_                      |
+//  +-+--------------+---------------+-----------------------+-+
+//    |              |               |                       |
+//    |              v               v                       v
+//    v    +-------------------+  +---------------------+  +-----------------+
+//   ...   | non_client_layer_ |  | web_contents_layer_ |  | devtools_layer_ |
+//         +-------------------+  +---------------------+  +-----------------+
+//
+//
+// Layout of the layer tree when effect is active:
+//  +---------------------+
+//  |     frame_layer_    |
+//  +-+---------------+---+
+//    |               |
+//    |               v
+//    v        +-------------------------------------------------+
+//   ...       |              frame_clipping_layer_              |
+//             +-----+--------------+---------------------+------+
+//                   |              |                     |
+//                   v              v                     V
+//     +-------------------+  +---------------------+  +-----------------+
+//     | non_client_layer_ |  | web_clipping_layer_ |  | devtools_layer_ |
+//     +-------------------+  +---------+-----------+  +-----------------+
+//                                      |
+//                                      v
+//                            +---------------------+
+//                            | web_contents_layer_ |
+//                            +---------------------+
+
+ScrollEndEffectController* ScrollEndEffectController::Create(
+    ScrollEndEffectControllerDelegate* delegate) {
+  return new ScrollEndEffectControllerAsh(delegate);
+}
+
+ScrollEndEffectControllerAsh::ScrollEndEffectControllerAsh(
+    ScrollEndEffectControllerDelegate* delegate)
+    : delegate_(delegate),
+      is_effect_active_(false),
+      frame_layer_(NULL),
+      non_client_layer_(NULL),
+      web_contents_layer_(NULL),
+      devtools_layer_(NULL),
+      web_contents_parent_(NULL),

[sky, 2013/09/05 21:12:57]

Make sure you initialize everything (looks like you're missing some, including
download_layer_...)

[rharrison, 2013/09/09 20:01:17]

Done.

+      devtools_parent_(NULL),
+      non_client_view_(NULL),
+      start_delta_y_(0),
+      current_delta_y_(0),
+      end_delta_y_(0) {
+  animation_.reset(new ui::SlideAnimation(this));
+  animation_->SetSlideDuration(100);
+  animation_->SetTweenType(ui::Tween::EASE_OUT);
 }
 
 ScrollEndEffectControllerAsh::~ScrollEndEffectControllerAsh() {
+  if (is_effect_active_)
+    DeactivateEffect();

[sky, 2013/09/05 21:12:57]

Did you verify you don't crash if you end up here? I ask as I suspect you do,
but I'm not positive. In particular I think some of the views you're using have
since been destroyed by the time you get here.

[rharrison, 2013/09/09 20:01:17]

It does crash, removed the code, since I don't think it is needed.

 }
 
 void ScrollEndEffectControllerAsh::OverscrollUpdate(int delta_y) {
-  // TODO(rharrison): Implement initial version of scroll end effect
-}
+  if (delegate_ == NULL)

[sky, 2013/09/05 21:12:57]

You never delegate_ to NULL, so why this check?

[rharrison, 2013/09/09 20:01:17]

Done.

+    return;
+
+  if (!is_effect_active_ && delta_y == 0)
+    return;
+
+  frame_layer_ = delegate_->GetBrowserFrameLayer();

[sky, 2013/09/05 21:12:57]

Seems like you should only set frame_layer_ if you're going to activate.

[rharrison, 2013/09/09 20:01:17]

Done.

+  if (!frame_layer_)
+    return;
+
+  if (!is_effect_active_)
+    ActivateEffect();
+
+  int capped_delta_y = delta_y;
+  gfx::Rect bounds = 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);
+  }
+
+  start_delta_y_ = current_delta_y_;
+  end_delta_y_ = capped_delta_y;
+  if (end_delta_y_ == 0) {
+    animation_->Reset();
+    animation_->Show();
+  } else {
+    animation_->Reset();
+    ApplyDelta(end_delta_y_);
+  }
+}
+
+void ScrollEndEffectControllerAsh::AnimationEnded(
+    const ui::Animation* animation) {
+  if (current_delta_y_ == 0)
+    DeactivateEffect();
+}
+
+void ScrollEndEffectControllerAsh::AnimationProgressed(
+    const ui::Animation* animation) {
+  ApplyDelta(ui::Tween::ValueBetween(animation_->GetCurrentValue(),
+                                     start_delta_y_,
+                                     end_delta_y_));
+}
+
+void ScrollEndEffectControllerAsh::ActivateEffect() {
+  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_ = download_view_ ? CreateViewLayer(download_view_) :
+      NULL;
+
+  CHECK(non_client_layer_);

[sky, 2013/09/05 21:12:57]

DCHECK on these

[rharrison, 2013/09/09 20:01:17]

Done.

+  CHECK(web_contents_layer_);
+  CHECK(devtools_layer_);
+
+  frame_clipping_layer_.reset(CreateClippingLayer(
+      "OverscrollFrameClippingLayer"));
+  web_clipping_layer_.reset(CreateClippingLayer("OverscrollWebClippingLayer"));
+
+  // Save bounds for restoring later
+  devtools_bounds_ = devtools_layer_->bounds();

[sky, 2013/09/05 21:12:57]

How do you know these bounds are going to be right at the time you're done?

[rharrison, 2013/09/09 20:01:17]

The size of the devtools area should not change during the effect since anything
like typing or moving another input device will cause overscroll to end and by
association the effect. I am not aware of a mechanism to change the devtools
size without user intervention. 

If you are thinking of a specific case please let me know.

+  web_contents_bounds_ = web_contents_layer_->bounds();
+
+  // Adjust the toplogy of the layer tree to add clipping layers

[sky, 2013/09/05 21:12:57]

toplogy->hierarchy

[rharrison, 2013/09/09 20:01:17]

Done.

+  devtools_parent_ = devtools_layer_->parent();
+  web_contents_parent_ = web_contents_layer_->parent();
+  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_);
+  if (download_layer_)
+    frame_clipping_layer_->Add(download_layer_);
+  web_clipping_layer_->Add(web_contents_layer_);

[sky, 2013/09/05 21:12:57]

This all strikes me as very fragile. In particular BrowserView and related
classes were to add/remove a view then all this is going to break.

It feels wrong that you have to mess with the layer tree to this degree to get
the effect you're after. Seems safer it things could be set up initially to
match what you're after so you don't have to shuffle things around. Maybe with
extra views in the hierarchy that you toggle layered painting on/off.

[rharrison, 2013/09/09 20:01:17]

I agree this is relatively brittle. If I recall correctly when we attempted
something like that I encountered cases (creating new tabs comes to mind
immediately) where other pieces of code made assumptions about the hierarchy and
things broke/crashed. The fact that the user cannot effectively interact with
the browser while overscrolling led to the idea of just making the changes that
are needed while the effect is active.

If you think this approach is too brittle, then I will abandon this CL.

[sky, 2013/09/11 00:13:39]

I don't think you need to abandon this CL entirely. I think you should set up
the view hierarchy at construction of BrowserView time in such a way that you
don't need to shuffle around the layer tree. In particular add extra views that
are always there and exist solely so you can turn on clipping while doing this
animation. The immersive mode mode went a similar way and it made for less
brittle code.

Alternatively perhaps you could adjust the clip on the actual view layers.

+}
+
+void ScrollEndEffectControllerAsh::DeactivateEffect() {
+  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;
+
+  if (download_layer_) {
+    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();
+  frame_layer_->Remove(frame_clipping_layer_.get());
+  frame_clipping_layer_.reset();
+}
+
+void ScrollEndEffectControllerAsh::ApplyDelta(int delta_y) {
+  current_delta_y_ = delta_y;
+  SetBoundsForEffect();
+
+  ui::Layer* frame = delegate_->GetBrowserFrameLayer();

[sky, 2013/09/05 21:12:57]

Isn't this frame_layer_?

[rharrison, 2013/09/09 20:01:17]

Done.

+  gfx::Rect bounds = frame->bounds();
+
+  float scale_factor = std::abs(delta_y);
+  scale_factor /= bounds.height();
+  scale_factor = 1 - scale_factor;
+
+  bool scrolling_down = delta_y > 0;
+  gfx::Transform frame_transform;
+  if (scrolling_down) {
+    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);
+
+  if (!download_layer_) {
+    download_view_ = delegate_->GetDownloadView();
+    download_layer_ = download_view_ ? CreateViewLayer(download_view_) :
+        NULL;
+  }
+  if (download_layer_) {
+    gfx::Transform download_transform =
+        CounterTransfromAboutPoint(0,
+                                   download_layer_->bounds().origin().y());
+    if (!scrolling_down)
+      download_transform.Translate(0, delta_y);
+    download_layer_->SetTransform(download_transform);
+  }
+
+  gfx::Transform devtools_transform =
+      CounterTransfromAboutPoint(0,
+                                 devtools_layer_->bounds().origin().y());
+  if (!scrolling_down)
+    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 (scrolling_down)
+    web_clipping_transform.Translate(0, delta_y);
+  web_clipping_layer_->SetTransform(web_clipping_transform);
+
+  if (!scrolling_down) {
+    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 (scrolling_down)
+    non_client_transform.Translate(0, delta_y);
+  non_client_layer_->SetTransform(non_client_transform);
+}
+
+void ScrollEndEffectControllerAsh::SetBoundsForEffect() {
+  gfx::Rect frame_clipping_bounds = frame_layer_->bounds();
+  frame_clipping_bounds.set_origin(gfx::Point());
+  frame_clipping_layer_->SetBounds(frame_clipping_bounds);
+
+  gfx::Rect web_clipping_bounds = frame_layer_->bounds();
+  int download_height = GetDownloadHeight();
+  int non_client_top_height = frame_layer_->bounds().height() -
+      web_contents_layer_->bounds().height() -
+      delegate_->GetDevToolsHeight() -
+      delegate_->GetDividerHeight() -
+      download_height;
+  int web_clipping_height = 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 = frame_layer_->bounds();
+  devtools_bounds.set_origin(gfx::Point(0,
+                                        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());
+  web_contents_layer_->SetBounds(web_contents_bounds);
+}
+
+int ScrollEndEffectControllerAsh::GetDownloadHeight() const  {
+  return !download_view_ ? 0 :

[sky, 2013/09/05 21:12:57]

nit:

  return download_view_ && download_view_->visible() ?
download_view_->bounds().height() : 0

is a lot easier to read.

[rharrison, 2013/09/09 20:01:17]

Done.

+      !download_view_->visible() ? 0 :
+      download_view_->bounds().height();
+}
+
+gfx::Transform ScrollEndEffectControllerAsh::CounterTransfromAboutPoint(int x,

[sky, 2013/09/05 21:12:57]

transform and const

[rharrison, 2013/09/09 20:01:17]

Done.

+                                                                        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;
+}