OverscrollController consumes scroll updates only during gesture-nav.

content/browser/renderer_host/overscroll_controller.cc

 // Copyright (c) 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 "content/browser/renderer_host/overscroll_controller.h"
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "content/browser/renderer_host/overscroll_controller_delegate.h"
 #include "content/public/browser/overscroll_configuration.h"
@@ skipping 204 matching lines @@
 
       ProcessOverscroll(wheel.deltaX * wheel.accelerationRatioX,
                         wheel.deltaY * wheel.accelerationRatioY,
                         wheel.type);
       event_processed = true;
       break;
     }
     case blink::WebInputEvent::GestureScrollUpdate: {
       const blink::WebGestureEvent& gesture =
           static_cast<const blink::WebGestureEvent&>(event);
-      ProcessOverscroll(gesture.data.scrollUpdate.deltaX,
-                        gesture.data.scrollUpdate.deltaY,
-                        gesture.type);
-      event_processed = true;
+      event_processed = ProcessOverscroll(gesture.data.scrollUpdate.deltaX,
+                                          gesture.data.scrollUpdate.deltaY,
+                                          gesture.type);
       break;
     }
     case blink::WebInputEvent::GestureFlingStart: {
       const float kFlingVelocityThreshold = 1100.f;
       const blink::WebGestureEvent& gesture =
           static_cast<const blink::WebGestureEvent&>(event);
       float velocity_x = gesture.data.flingStart.velocityX;
       float velocity_y = gesture.data.flingStart.velocityY;
       if (fabs(velocity_x) > kFlingVelocityThreshold) {
         if ((overscroll_mode_ == OVERSCROLL_WEST && velocity_x < 0) ||
@@ skipping 17 matching lines @@
     }
 
     default:
       DCHECK(blink::WebInputEvent::isGestureEventType(event.type) ||
              blink::WebInputEvent::isTouchEventType(event.type))
           << "Received unexpected event: " << event.type;
   }
   return event_processed;
 }
 
-void OverscrollController::ProcessOverscroll(float delta_x,
+bool OverscrollController::ProcessOverscroll(float delta_x,
                                              float delta_y,
                                              blink::WebInputEvent::Type type) {
   if (scroll_state_ != STATE_CONTENT_SCROLLING)
     overscroll_delta_x_ += delta_x;
   overscroll_delta_y_ += delta_y;
 
   float horiz_threshold = GetOverscrollConfig(
       WebInputEvent::isGestureEventType(type) ?
           OVERSCROLL_CONFIG_HORIZ_THRESHOLD_START_TOUCHSCREEN :
           OVERSCROLL_CONFIG_HORIZ_THRESHOLD_START_TOUCHPAD);
   float vert_threshold = GetOverscrollConfig(
       OVERSCROLL_CONFIG_VERT_THRESHOLD_START);
   if (fabs(overscroll_delta_x_) <= horiz_threshold &&
       fabs(overscroll_delta_y_) <= vert_threshold) {
     SetOverscrollMode(OVERSCROLL_NONE);
-    return;
+    return false;
   }
 
   // Compute the current overscroll direction. If the direction is different
   // from the current direction, then always switch to no-overscroll mode first
   // to make sure that subsequent scroll events go through to the page first.
   OverscrollMode new_mode = OVERSCROLL_NONE;
   const float kMinRatio = 2.5;
   if (fabs(overscroll_delta_x_) > horiz_threshold &&
       fabs(overscroll_delta_x_) > fabs(overscroll_delta_y_) * kMinRatio)
     new_mode = overscroll_delta_x_ > 0.f ? OVERSCROLL_EAST : OVERSCROLL_WEST;
   else if (fabs(overscroll_delta_y_) > vert_threshold &&
            fabs(overscroll_delta_y_) > fabs(overscroll_delta_x_) * kMinRatio)
     new_mode = overscroll_delta_y_ > 0.f ? OVERSCROLL_SOUTH : OVERSCROLL_NORTH;
 
   // The vertical oversrcoll currently does not have any UX effects other then
   // for the scroll end effect, so testing if it is enabled.
   if ((new_mode == OVERSCROLL_SOUTH || new_mode == OVERSCROLL_NORTH) &&
       !IsScrollEndEffectEnabled())
     new_mode = OVERSCROLL_NONE;
 
   if (overscroll_mode_ == OVERSCROLL_NONE)
     SetOverscrollMode(new_mode);
   else if (new_mode != overscroll_mode_)
     SetOverscrollMode(OVERSCROLL_NONE);
 
   if (overscroll_mode_ == OVERSCROLL_NONE)
-    return;
+    return false;
 
   // Tell the delegate about the overscroll update so that it can update
   // the display accordingly (e.g. show history preview etc.).
   if (delegate_) {
     // Do not include the threshold amount when sending the deltas to the
     // delegate.
     float delegate_delta_x = overscroll_delta_x_;
     if (fabs(delegate_delta_x) > horiz_threshold) {
       if (delegate_delta_x < 0)
         delegate_delta_x += horiz_threshold;
       else
         delegate_delta_x -= horiz_threshold;
     } else {
       delegate_delta_x = 0.f;
     }
 
     float delegate_delta_y = overscroll_delta_y_;
     if (fabs(delegate_delta_y) > vert_threshold) {
       if (delegate_delta_y < 0)
         delegate_delta_y += vert_threshold;
       else
         delegate_delta_y -= vert_threshold;
     } else {
       delegate_delta_y = 0.f;
     }
-    delegate_->OnOverscrollUpdate(delegate_delta_x, delegate_delta_y);
+    return delegate_->OnOverscrollUpdate(delegate_delta_x, delegate_delta_y);
   }
+  return false;
 }
 
 void OverscrollController::CompleteAction() {
   if (delegate_)
     delegate_->OnOverscrollComplete(overscroll_mode_);
   overscroll_mode_ = OVERSCROLL_NONE;
   overscroll_delta_x_ = overscroll_delta_y_ = 0.f;
 }
 
 void OverscrollController::SetOverscrollMode(OverscrollMode mode) {
   if (overscroll_mode_ == mode)
     return;
   OverscrollMode old_mode = overscroll_mode_;
   overscroll_mode_ = mode;
   if (overscroll_mode_ == OVERSCROLL_NONE)
     overscroll_delta_x_ = overscroll_delta_y_ = 0.f;
   else
     scroll_state_ = STATE_OVERSCROLLING;
   if (delegate_)
     delegate_->OnOverscrollModeChange(old_mode, overscroll_mode_);
 }
 
 }  // namespace content