Add support for calculating the position of the top controls in the cc layer.

cc/top_controls_manager.cc

+// Copyright 2012 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 "cc/top_controls_manager.h"
+
+#include <algorithm>
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/logging.h"
+#include "base/time.h"
+#include "cc/layer_tree_impl.h"
+#include "cc/top_controls_animation.h"
+#include "cc/top_controls_manager_client.h"
+#include "ui/gfx/transform.h"
+#include "ui/gfx/vector2d_f.h"
+
+namespace cc {
+namespace {
+const float kShowHideThreshold = 0.75f;

[jamesr, 2013/01/08 02:26:48]

can you leave a comment here saying where these numbers came from and how they
can be changed? even if the answers are "picked empirically" and "email
tedchoc@chromium.org" having that here will help future generations

[Ted C, 2013/01/08 18:17:33]

Done.

+const int64 kAutoHideDelayMs = 1500;
+const int64 kShowHideMaxDurationMs = 500;
+}
+
+// static
+scoped_ptr<TopControlsManager> TopControlsManager::Create(
+    TopControlsManagerClient* client, float top_controls_height) {
+  return make_scoped_ptr(new TopControlsManager(client, top_controls_height));
+}
+
+TopControlsManager::TopControlsManager(TopControlsManagerClient* client,
+                                       float top_controls_height)
+    : client_(client),
+      is_overlay_mode_(false),
+      top_controls_height_(top_controls_height),
+      controls_top_offset_(0),
+      content_top_offset_(top_controls_height),
+      previous_root_scroll_offset_(0.f),
+      scroll_readjustment_enabled_(false) {
+  CHECK(client_);
+}
+
+TopControlsManager::~TopControlsManager() {
+}
+
+void TopControlsManager::UpdateDrawPositions() {
+  if (!RootScrollLayer())
+    return;
+
+  // If the scroll position has changed underneath us (i.e. a javascript
+  // scroll), then simulate a scroll that covers the delta.
+  float scroll_total_y = RootScrollLayerTotalScrollY();
+  if (scroll_readjustment_enabled_
+      && scroll_total_y != previous_root_scroll_offset_) {
+    ScrollBy(gfx::Vector2dF(0, scroll_total_y - previous_root_scroll_offset_));
+    StartAnimationIfNecessary();
+    previous_root_scroll_offset_ = RootScrollLayerTotalScrollY();
+  }
+
+  float offset_top = is_overlay_mode_ ? 0 : content_top_offset_;
+
+  // The two layers that need to be transformed are the clip layer and root
+  // scrollbar layers, which are the only two children of the root layer.
+  LayerImpl* root_layer = client_->activeTree()->RootLayer();
+  for (size_t i = 0; i < root_layer->children().size(); ++i) {
+    LayerImpl* child_layer = root_layer->children()[i];
+    gfx::Transform transform;
+    transform.Translate(0, offset_top);
+    child_layer->setImplTransform(transform);

[enne (OOO), 2013/01/08 06:23:05]

It seems more than a little dangerous that the top controls manager reaching in
and mucking with the layer tree.  This sort of code will break.

Especially with the TODO "Adjust fixed position layers as well.", it seems like
you're trying to work around calcDrawProperties and the layer tree and property
system.  Can what you're trying to do be acheived by adding some LayerImpls to
the tree?

[Ted C, 2013/01/08 18:17:33]

For adjusting the fixed position layers, that might not be changes done here but
instead fixing up how we calculate their relative position in calcDrawProperties
when translating/resizing parent layers.

+  }
+
+  // TODO(tedchoc): Adjust fixed position layers as well.
+}
+
+void TopControlsManager::ScrollBegin() {
+  ResetAnimations();
+  scroll_readjustment_enabled_ = false;
+}
+
+gfx::Vector2dF TopControlsManager::ScrollBy(
+    const gfx::Vector2dF pending_delta) {
+  ResetAnimations();
+  return ScrollInternal(pending_delta);
+}
+
+gfx::Vector2dF TopControlsManager::ScrollInternal(
+    const gfx::Vector2dF pending_delta) {
+  float scroll_total_y = RootScrollLayerTotalScrollY();
+  float scroll_delta_y = pending_delta.y();
+
+  float previous_controls_offset = controls_top_offset_;
+  float previous_content_offset = content_top_offset_;
+  bool previous_was_overlay = is_overlay_mode_;
+
+  controls_top_offset_ -= scroll_delta_y;
+  controls_top_offset_ = std::min(
+      std::max(controls_top_offset_, -top_controls_height_), 0.f);
+
+  if (scroll_total_y > 0 || (scroll_total_y == 0
+      && content_top_offset_ < scroll_delta_y)) {
+    is_overlay_mode_ = true;
+    content_top_offset_ = 0;
+  } else if (scroll_total_y <= 0 && (scroll_delta_y < 0
+      || (scroll_delta_y > 0 && content_top_offset_ > 0))) {
+    is_overlay_mode_ = false;
+    content_top_offset_ -= scroll_delta_y;
+  }
+  content_top_offset_ = std::max(
+      std::min(content_top_offset_,
+               controls_top_offset_ + top_controls_height_), 0.f);
+
+  gfx::Vector2dF applied_delta;
+  if (!previous_was_overlay)
+    applied_delta.set_y(previous_content_offset - content_top_offset_);
+
+  if (is_overlay_mode_ != previous_was_overlay
+      || previous_controls_offset != controls_top_offset_
+      || previous_content_offset != content_top_offset_) {
+    client_->setNeedsRedraw();
+    client_->setNeedsUpdateDrawProperties();
+  }
+
+  return pending_delta - applied_delta;
+}
+
+void TopControlsManager::ScrollEnd() {
+  StartAnimationIfNecessary();
+  previous_root_scroll_offset_ = RootScrollLayerTotalScrollY();
+  scroll_readjustment_enabled_ = true;
+}
+
+void TopControlsManager::Animate(base::TimeTicks monotonic_time) {
+  if (!top_controls_animation_ || !RootScrollLayer())
+    return;
+
+  double time = (monotonic_time - base::TimeTicks()).InSecondsF();
+  float new_offset =
+      top_controls_animation_->ScrollOffsetAtTime(monotonic_time);
+  gfx::Vector2dF scroll_vector(0.f, -(new_offset - controls_top_offset_));
+  ScrollInternal(scroll_vector);
+  client_->setNeedsRedraw();
+
+  if (top_controls_animation_->IsAnimationCompleteAtTime(monotonic_time)) {
+    top_controls_animation_.reset();
+    StartAnimationIfNecessary();
+  }
+}
+
+void TopControlsManager::ResetAnimations() {
+  if (top_controls_animation_)
+    top_controls_animation_.reset();
+  auto_hide_timer_.Stop();
+}
+
+LayerImpl* TopControlsManager::RootScrollLayer() {
+  return client_->activeTree()->root_scroll_layer();
+}
+
+float TopControlsManager::RootScrollLayerTotalScrollY() {
+  LayerImpl* layer = RootScrollLayer();
+  if (!layer)
+    return 0;
+  gfx::Vector2dF scroll_total = layer->scrollOffset() + layer->scrollDelta();
+  return scroll_total.y();
+}
+
+void TopControlsManager::StartAnimationIfNecessary() {
+  if (!is_overlay_mode_)
+    return;
+
+  float scroll_total_y = RootScrollLayerTotalScrollY();
+
+  if (controls_top_offset_ != 0
+      && controls_top_offset_ != -top_controls_height_) {
+    top_controls_animation_ = TopControlsAnimation::Create(
+        controls_top_offset_,
+        top_controls_height_,
+        base::TimeTicks::Now(),
+        base::TimeDelta::FromMilliseconds(kShowHideMaxDurationMs));
+    top_controls_animation_->SetDirection(
+        controls_top_offset_ >= -(top_controls_height_ * kShowHideThreshold));
+    client_->setNeedsRedraw();
+  } else if (controls_top_offset_ == 0 && scroll_total_y != 0) {
+    auto_hide_timer_.Stop();
+    auto_hide_timer_.Start(FROM_HERE,
+                           base::TimeDelta::FromMilliseconds(kAutoHideDelayMs),
+                           this,
+                           &TopControlsManager::StartAutoHideAnimation);
+  }
+}
+
+void TopControlsManager::StartAutoHideAnimation() {
+  top_controls_animation_ = TopControlsAnimation::Create(
+      controls_top_offset_,
+      top_controls_height_,
+      base::TimeTicks::Now(),
+      base::TimeDelta::FromMilliseconds(kShowHideMaxDurationMs));
+  top_controls_animation_->SetDirection(false);
+  client_->setNeedsRedraw();
+}
+
+}  // namespace cc