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

cc/top_controls_manager.cc

Index: cc/top_controls_manager.cc
diff --git a/cc/top_controls_manager.cc b/cc/top_controls_manager.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a46103f407a3a016690d11996a51e2372df85885
--- /dev/null
+++ b/cc/top_controls_manager.cc
@@ -0,0 +1,194 @@
+// 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/logging.h"
+#include "base/time.h"
+#include "cc/keyframed_animation_curve.h"
+#include "cc/layer_tree_impl.h"
+#include "cc/timing_function.h"
+#include "cc/top_controls_manager_client.h"
+#include "ui/gfx/transform.h"
+#include "ui/gfx/vector2d_f.h"
+
+namespace cc {
+namespace {
+// These constants were chosen empirically for their visually pleasant behavior.
+// Contact tedchoc@chromium.org for questions about changing these values.
+const float kShowHideThreshold = 0.75f;
+const int64 kShowHideMaxDurationMs = 250;
+}
+
+// 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),
+      content_layer_id_(0),
+      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),
+      is_showing_animation_(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_;
+
+  LayerImpl* content_layer =
+      client_->activeTree()->FindActiveTreeLayerById(content_layer_id_);
+  DCHECK(content_layer);
+  if (content_layer) {
+    gfx::Transform transform;
+    transform.Translate(0, offset_top);
+    content_layer->setTransform(transform);
+  }
+
+  // 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()).InMillisecondsF();
+  float new_offset = top_controls_animation_->getValue(time);
+  gfx::Vector2dF scroll_vector(0.f, -(new_offset - controls_top_offset_));
+  ScrollInternal(scroll_vector);
+  client_->setNeedsRedraw();
+
+  if ((is_showing_animation_ && new_offset >= 0) ||
+      (!is_showing_animation_ && new_offset <= -top_controls_height_)) {
+    top_controls_animation_.reset();
+    StartAnimationIfNecessary();
+  }
+}
+
+void TopControlsManager::ResetAnimations() {
+  if (top_controls_animation_)
+    top_controls_animation_.reset();
+}
+
+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::SetupAnimation(bool show_controls) {
+  top_controls_animation_ = KeyframedFloatAnimationCurve::create();
+  double start_time =
+      (base::TimeTicks::Now() - base::TimeTicks()).InMillisecondsF();
+  top_controls_animation_->addKeyframe(
+      FloatKeyframe::create(start_time, controls_top_offset_,
+                            scoped_ptr<TimingFunction>()));
+  float max_ending_offset = (show_controls ? 1 : -1) * top_controls_height_;
+  top_controls_animation_->addKeyframe(
+      FloatKeyframe::create(start_time + kShowHideMaxDurationMs,
+                            controls_top_offset_ + max_ending_offset,
+                            EaseTimingFunction::create()));
+  is_showing_animation_ = show_controls;
+}
+
+void TopControlsManager::StartAnimationIfNecessary() {
+  float scroll_total_y = RootScrollLayerTotalScrollY();
+
+  if (controls_top_offset_ != 0
+      && controls_top_offset_ != -top_controls_height_) {
+    SetupAnimation(
+        controls_top_offset_ >= -(top_controls_height_ * kShowHideThreshold));
+    client_->setNeedsRedraw();
+  }
+}
+
+}  // namespace cc