New AppListView Scroll Behavior.

ui/app_list/pagination_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 "ui/app_list/pagination_controller.h"
 
 #include "ui/app_list/pagination_model.h"
 #include "ui/events/event.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/vector2d.h"
 
 namespace app_list {
 
 namespace {
 
 // Constants for dealing with scroll events.
 const int kMinScrollToSwitchPage = 20;
 const int kMinHorizVelocityToSwitchPage = 800;
 
 const double kFinishTransitionThreshold = 0.33;
 
 }  // namespace
 
 PaginationController::PaginationController(PaginationModel* model,
                                            ScrollAxis scroll_axis)
-    : pagination_model_(model), scroll_axis_(scroll_axis) {
-}
+    : pagination_model_(model), scroll_axis_(scroll_axis) {}
 
 bool PaginationController::OnScroll(const gfx::Vector2d& offset,
                                     ScrollEventType type) {
   int offset_magnitude;
   if (scroll_axis_ == SCROLL_AXIS_HORIZONTAL) {
     // If the view scrolls horizontally, both horizontal and vertical scroll
     // events are valid (since most mouse wheels only have vertical scrolling).
     offset_magnitude =
         abs(offset.x()) > abs(offset.y()) ? offset.x() : offset.y();
   } else {
     // If the view scrolls vertically, only vertical scroll events are valid.
     offset_magnitude = offset.y();
   }
 
   // Do not scroll on very small events.
   // TODO(calamity): This should only apply on touchpad scroll but touchpad
   // events are coming in as mousewheel events. See https://crbug.com/594264.
-  if (abs(offset_magnitude) > kMinScrollToSwitchPage) {
-    if (!pagination_model_->has_transition()) {
-      pagination_model_->SelectPageRelative(offset_magnitude > 0 ? -1 : 1,
-                                            true);
-    }
+  if (abs(offset_magnitude) > kMinScrollToSwitchPage &&

[khmel, 2017/07/14 18:10:01]

nit: I would not do just only style fix and prefer to leave file un-touch to
simplify the review. Have no strong pref here. You may also leave it.

[newcomer, 2017/07/17 21:38:10]

I actually am fixing a bug here (returning true inside the if statement, else
returning false). This conditional was preventing scroll events from propogating
to AppListView.

+      !pagination_model_->has_transition()) {
+    pagination_model_->SelectPageRelative(offset_magnitude > 0 ? -1 : 1, true);
     return true;
   }
 
   return false;
 }
 
 bool PaginationController::OnGestureEvent(const ui::GestureEvent& event,
                                           const gfx::Rect& bounds) {
   const ui::GestureEventDetails& details = event.details();
   switch (event.type()) {
@@ skipping 23 matching lines @@
       if (fabs(velocity) > kMinHorizVelocityToSwitchPage)
         pagination_model_->SelectPageRelative(velocity < 0 ? 1 : -1, true);
       return true;
     }
     default:
       return false;
   }
 }
 
 }  // namespace app_list