Reland of Show Overlay Scrollbar when GestureScrollUpdate

cc/input/scrollbar_animation_controller.cc

 // Copyright 2014 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/input/scrollbar_animation_controller.h"
 
 #include <algorithm>
 
 #include "base/time/time.h"
 #include "cc/trees/layer_tree_impl.h"
@@ skipping 32 matching lines @@
     base::TimeDelta fade_out_delay,
     base::TimeDelta fade_out_resize_delay,
     base::TimeDelta fade_out_duration)
     : client_(client),
       fade_out_delay_(fade_out_delay),
       fade_out_resize_delay_(fade_out_resize_delay),
       need_trigger_scrollbar_show_(false),
       is_animating_(false),
       scroll_layer_id_(scroll_layer_id),
       currently_scrolling_(false),
-      scroll_gesture_has_scrolled_(false),
+      show_in_fast_scroll_(false),
       opacity_(0.0f),
       fade_out_duration_(fade_out_duration),
+      show_scrollbars_on_scroll_gesture_(false),
       need_thinning_animation_(false),
       weak_factory_(this) {
   ApplyOpacityToScrollbars(0.0f);
 }
 
 ScrollbarAnimationController::ScrollbarAnimationController(
     int scroll_layer_id,
     ScrollbarAnimationControllerClient* client,
     base::TimeDelta show_delay,
     base::TimeDelta fade_out_delay,
     base::TimeDelta fade_out_resize_delay,
     base::TimeDelta fade_out_duration,
     base::TimeDelta thinning_duration)
     : client_(client),
       show_delay_(show_delay),
       fade_out_delay_(fade_out_delay),
       fade_out_resize_delay_(fade_out_resize_delay),
       need_trigger_scrollbar_show_(false),
       is_animating_(false),
       scroll_layer_id_(scroll_layer_id),
       currently_scrolling_(false),
-      scroll_gesture_has_scrolled_(false),
+      show_in_fast_scroll_(false),
       opacity_(0.0f),
       fade_out_duration_(fade_out_duration),
+      show_scrollbars_on_scroll_gesture_(true),
       need_thinning_animation_(true),
       weak_factory_(this) {
   vertical_controller_ = SingleScrollbarAnimationControllerThinning::Create(
       scroll_layer_id, ScrollbarOrientation::VERTICAL, client,
       thinning_duration);
   horizontal_controller_ = SingleScrollbarAnimationControllerThinning::Create(
       scroll_layer_id, ScrollbarOrientation::HORIZONTAL, client,
       thinning_duration);
   ApplyOpacityToScrollbars(0.0f);
 }
@@ skipping 23 matching lines @@
 }
 
 void ScrollbarAnimationController::StopAnimation() {
   delayed_scrollbar_show_.Cancel();
   delayed_scrollbar_fade_out_.Cancel();
   is_animating_ = false;
 }
 
 void ScrollbarAnimationController::PostDelayedShow() {
   DCHECK(delayed_scrollbar_fade_out_.IsCancelled());
+  delayed_scrollbar_show_.Cancel();
   delayed_scrollbar_show_.Reset(base::Bind(&ScrollbarAnimationController::Show,
                                            weak_factory_.GetWeakPtr()));
   client_->PostDelayedScrollbarAnimationTask(delayed_scrollbar_show_.callback(),
                                              show_delay_);
 }
 
 void ScrollbarAnimationController::PostDelayedFadeOut(bool on_resize) {
   DCHECK(delayed_scrollbar_show_.IsCancelled());
   base::TimeDelta delay = on_resize ? fade_out_resize_delay_ : fade_out_delay_;
+  delayed_scrollbar_fade_out_.Cancel();
   delayed_scrollbar_fade_out_.Reset(
       base::Bind(&ScrollbarAnimationController::StartAnimation,
                  weak_factory_.GetWeakPtr()));
   client_->PostDelayedScrollbarAnimationTask(
       delayed_scrollbar_fade_out_.callback(), delay);
 }
 
 bool ScrollbarAnimationController::Animate(base::TimeTicks now) {
   bool animated = false;
 
@@ skipping 17 matching lines @@
   return animated;
 }
 
 float ScrollbarAnimationController::AnimationProgressAtTime(
     base::TimeTicks now) {
   base::TimeDelta delta = now - last_awaken_time_;
   float progress = delta.InSecondsF() / fade_out_duration_.InSecondsF();
   return std::max(std::min(progress, 1.f), 0.f);
 }
 
-void ScrollbarAnimationController::DidScrollBegin() {
-  currently_scrolling_ = true;
-}
-
 void ScrollbarAnimationController::RunAnimationFrame(float progress) {
   ApplyOpacityToScrollbars(1.f - progress);
   if (progress == 1.f)
     StopAnimation();
 }
 
-void ScrollbarAnimationController::DidScrollUpdate(bool on_resize) {
+void ScrollbarAnimationController::DidScrollBegin() {
+  currently_scrolling_ = true;
+}
+
+void ScrollbarAnimationController::DidScrollEnd() {
+  bool has_scrolled = show_in_fast_scroll_;
+  show_in_fast_scroll_ = false;
+
+  currently_scrolling_ = false;
+
+  // We don't fade out scrollbar if they need thinning animation and mouse is
+  // near.
+  if (need_thinning_animation_ && MouseIsNearAnyScrollbar())
+    return;
+
+  if (has_scrolled)
+    PostDelayedFadeOut(false);
+}
+
+void ScrollbarAnimationController::DidScrollUpdate() {
   if (need_thinning_animation_ && Captured())
     return;
 
   StopAnimation();
 
   // As an optimization, we avoid spamming fade delay tasks during active fast
   // scrolls.  But if we're not within one, we need to post every scroll update.
   if (!currently_scrolling_) {
     // We don't fade out scrollbar if they need thinning animation and mouse is
     // near.
     if (!need_thinning_animation_ || !MouseIsNearAnyScrollbar())
-      PostDelayedFadeOut(on_resize);
+      PostDelayedFadeOut(false);
   } else {
-    scroll_gesture_has_scrolled_ = true;
+    show_in_fast_scroll_ = true;
   }
 
   Show();
 
   if (need_thinning_animation_) {
     vertical_controller_->UpdateThumbThicknessScale();
     horizontal_controller_->UpdateThumbThicknessScale();
   }
 }
 
-void ScrollbarAnimationController::DidScrollEnd() {
-  bool has_scrolled = scroll_gesture_has_scrolled_;
-  scroll_gesture_has_scrolled_ = false;
+void ScrollbarAnimationController::WillUpdateScroll() {
+  if (show_scrollbars_on_scroll_gesture_)
+    DidScrollUpdate();
+}
 
-  currently_scrolling_ = false;
+void ScrollbarAnimationController::DidResize() {
+  StopAnimation();
+  Show();
 
-  // We don't fade out scrollbar if they need thinning animation and mouse is
-  // near.
-  if (need_thinning_animation_ && MouseIsNearAnyScrollbar())
-    return;
-
-  if (has_scrolled)
-    PostDelayedFadeOut(false);
+  // As an optimization, we avoid spamming fade delay tasks during active fast
+  // scrolls.
+  if (!currently_scrolling_) {
+    PostDelayedFadeOut(true);
+  } else {
+    show_in_fast_scroll_ = true;
+  }
 }
 
 void ScrollbarAnimationController::DidMouseDown() {
   if (!need_thinning_animation_ || ScrollbarsHidden())
     return;
 
   vertical_controller_->DidMouseDown();
   horizontal_controller_->DidMouseDown();
 }
 
@@ skipping 139 matching lines @@
   if (opacity_ != opacity)
     client_->SetNeedsRedrawForScrollbarAnimation();
 
   opacity_ = opacity;
 
   if (previouslyVisible != currentlyVisible)
     client_->DidChangeScrollbarVisibility();
 }
 
 }  // namespace cc