Refactor app list scrolling: introduce the PaginationController class.

ui/app_list/views/apps_grid_view.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 "ui/app_list/views/apps_grid_view.h"
 
 #include <algorithm>
 #include <set>
 #include <string>
 
 #include "base/guid.h"
 #include "ui/app_list/app_list_constants.h"
 #include "ui/app_list/app_list_folder_item.h"
 #include "ui/app_list/app_list_item.h"
 #include "ui/app_list/app_list_switches.h"
+#include "ui/app_list/pagination_controller.h"
 #include "ui/app_list/views/app_list_drag_and_drop_host.h"
 #include "ui/app_list/views/app_list_folder_view.h"
 #include "ui/app_list/views/app_list_item_view.h"
 #include "ui/app_list/views/apps_grid_view_delegate.h"
 #include "ui/app_list/views/page_switcher.h"
 #include "ui/app_list/views/pulsing_block_view.h"
 #include "ui/app_list/views/top_icon_animation_view.h"
 #include "ui/compositor/scoped_layer_animation_settings.h"
 #include "ui/events/event.h"
 #include "ui/gfx/animation/animation.h"
+#include "ui/gfx/geometry/point.h"
 #include "ui/views/border.h"
 #include "ui/views/view_model_utils.h"
 #include "ui/views/widget/widget.h"
 
 #if defined(USE_AURA)
 #include "ui/aura/window.h"
 #include "ui/aura/window_event_dispatcher.h"
 #if defined(OS_WIN)
 #include "ui/views/win/hwnd_util.h"
 #endif  // defined(OS_WIN)
@@ skipping 49 matching lines @@
 // Delays in milliseconds to show re-order preview.
 const int kReorderDelay = 120;
 
 // Delays in milliseconds to show folder item reparent UI.
 const int kFolderItemReparentDelay = 50;
 
 // Radius of the circle, in which if entered, show folder dropping preview
 // UI.
 const int kFolderDroppingCircleRadius = 15;
 
-// Constants for dealing with scroll events.
-const int kMinMouseWheelToSwitchPage = 20;
-const int kMinScrollToSwitchPage = 20;
-const int kMinHorizVelocityToSwitchPage = 800;
-
-const double kFinishTransitionThreshold = 0.33;
-
 // RowMoveAnimationDelegate is used when moving an item into a different row.
 // Before running the animation, the item's layer is re-created and kept in
 // the original position, then the item is moved to just before its target
 // position and opacity set to 0. When the animation runs, this delegate moves
 // the layer and fades it out while fading in the item at the same time.
 class RowMoveAnimationDelegate : public gfx::AnimationDelegate {
  public:
   RowMoveAnimationDelegate(views::View* view,
                            ui::Layer* layer,
                            const gfx::Rect& layer_target)
@@ skipping 250 matching lines @@
   SetPaintToLayer(true);
   // Clip any icons that are outside the grid view's bounds. These icons would
   // otherwise be visible to the user when the grid view is off screen.
   layer()->SetMasksToBounds(true);
   SetFillsBoundsOpaquely(false);
 
   pagination_model_.SetTransitionDurations(kPageTransitionDurationInMs,
                                            kOverscrollPageTransitionDurationMs);
 
   pagination_model_.AddObserver(this);
+  // The experimental app list transitions vertically.
+  PaginationController::ScrollAxis scroll_axis =
+      app_list::switches::IsExperimentalAppListEnabled()
+          ? PaginationController::SCROLL_AXIS_VERTICAL
+          : PaginationController::SCROLL_AXIS_HORIZONTAL;
+  pagination_controller_.reset(
+      new PaginationController(&pagination_model_, scroll_axis));
   page_switcher_view_ = new PageSwitcher(&pagination_model_);
   AddChildView(page_switcher_view_);
 }
 
 AppsGridView::~AppsGridView() {
   // Coming here |drag_view_| should already be canceled since otherwise the
   // drag would disappear after the app list got animated away and closed,
   // which would look odd.
   DCHECK(!drag_view_);
   if (drag_view_)
@@ skipping 572 matching lines @@
 
 bool AppsGridView::OnKeyReleased(const ui::KeyEvent& event) {
   bool handled = false;
   if (selected_view_)
     handled = selected_view_->OnKeyReleased(event);
 
   return handled;
 }
 
 bool AppsGridView::OnMouseWheel(const ui::MouseWheelEvent& event) {
-  int offset;
-  if (GetScrollAxis() == SCROLL_AXIS_HORIZONTAL) {
-    // If the view scrolls horizontally, both horizontal and vertical scroll
-    // events are valid (since most mouse wheels only have vertical scrolling).
-    if (abs(event.x_offset()) > abs(event.y_offset()))
-      offset = event.x_offset();
-    else
-      offset = event.y_offset();
-  } else {
-    // If the view scrolls vertically, only vertical scroll events are valid.
-    offset = event.y_offset();
-  }
-
-  if (abs(offset) > kMinMouseWheelToSwitchPage) {
-    if (!pagination_model_.has_transition()) {
-      pagination_model_.SelectPageRelative(offset > 0 ? -1 : 1, true);
-    }
-    return true;
-  }
-
-  return false;
+  return pagination_controller_->OnScroll(
+      gfx::Point(event.x_offset(), event.y_offset()));
 }
 
 void AppsGridView::ViewHierarchyChanged(
     const ViewHierarchyChangedDetails& details) {
   if (!details.is_add && details.parent == this) {
     // The view being delete should not have reference in |view_model_|.
     CHECK_EQ(-1, view_model_.GetIndexOfView(details.child));
 
     if (selected_view_ == details.child)
       selected_view_ = NULL;
     if (activated_folder_item_view_ == details.child)
       activated_folder_item_view_ = NULL;
 
     if (drag_view_ == details.child)
       EndDrag(true);
 
     bounds_animator_.StopAnimatingView(details.child);
   }
 }
 
 void AppsGridView::OnGestureEvent(ui::GestureEvent* event) {
-  const ui::GestureEventDetails& details = event->details();
-  switch (event->type()) {
-    case ui::ET_GESTURE_SCROLL_BEGIN:
-      pagination_model_.StartScroll();
-      event->SetHandled();
-      return;
-    case ui::ET_GESTURE_SCROLL_UPDATE: {
-      float scroll = GetScrollAxis() == SCROLL_AXIS_HORIZONTAL
-                         ? details.scroll_x()
-                         : details.scroll_y();
-      gfx::Rect bounds(GetContentsBounds());
-      int size = GetScrollAxis() == SCROLL_AXIS_HORIZONTAL ? bounds.width()
-                                                           : bounds.height();
-      // scroll > 0 means moving contents right or down. That is, transitioning
-      // to the previous page.
-      pagination_model_.UpdateScroll(scroll / size);
-      event->SetHandled();
-      return;
-    }
-    case ui::ET_GESTURE_SCROLL_END:
-      pagination_model_.EndScroll(pagination_model_.transition().progress <
-                                  kFinishTransitionThreshold);
-      event->SetHandled();
-      return;
-    case ui::ET_SCROLL_FLING_START: {
-      float velocity = GetScrollAxis() == SCROLL_AXIS_HORIZONTAL
-                           ? details.velocity_x()
-                           : details.velocity_y();
-      pagination_model_.EndScroll(true);
-      if (fabs(velocity) > kMinHorizVelocityToSwitchPage)
-        pagination_model_.SelectPageRelative(velocity < 0 ? 1 : -1, true);
-      event->SetHandled();
-      return;
-    }
-    default:
-      break;
-  }
+  pagination_controller_->OnGestureEvent(event, GetContentsBounds());
 }
 
 void AppsGridView::OnScrollEvent(ui::ScrollEvent* event) {
   if (event->type() == ui::ET_SCROLL_FLING_CANCEL)
     return;
 
-  float offset;
-  if (GetScrollAxis() == SCROLL_AXIS_HORIZONTAL) {
-    // If the view scrolls horizontally, both horizontal and vertical scroll
-    // events are valid (vertical scroll events simulate mouse wheel).
-    if (std::abs(event->x_offset()) > std::abs(event->y_offset()))
-      offset = event->x_offset();
-    else
-      offset = event->y_offset();
-  } else {
-    // If the view scrolls vertically, only vertical scroll events are valid.
-    offset = event->y_offset();
-  }
-
-  if (std::abs(offset) > kMinScrollToSwitchPage) {
-    if (!pagination_model_.has_transition()) {
-      pagination_model_.SelectPageRelative(offset > 0 ? -1 : 1, true);
-    }
+  if (pagination_controller_->OnScroll(
+          gfx::Point(static_cast<int>(event->x_offset()),
+                     static_cast<int>(event->y_offset())))) {

[calamity, 2014/09/01 01:49:30]

Maybe gfx::ToFlooredPoint(gfx::PointF(event->x_offset(), event->y_offset()));

[Matt Giuca, 2014/09/01 03:02:26]

Done.

     event->SetHandled();
     event->StopPropagation();
   }
 }
 
 void AppsGridView::Update() {
   DCHECK(!selected_view_ && !drag_view_);
   view_model_.Clear();
   if (!item_list_ || !item_list_->item_count())
     return;
@@ skipping 187 matching lines @@
                  drop_attempt_ == DROP_FOR_REORDER) {
         ++slot_index;
         view_index = GetIndexFromModelIndex(slot_index);
       }
     }
 
     // Decide the x or y offset for current item.
     int x_offset = 0;
     int y_offset = 0;
 
-    if (GetScrollAxis() == SCROLL_AXIS_HORIZONTAL) {
+    if (pagination_controller_->scroll_axis() ==
+        PaginationController::SCROLL_AXIS_HORIZONTAL) {
       if (view_index.page < current_page)
         x_offset = -page_width;
       else if (view_index.page > current_page)
         x_offset = page_width;
 
       if (is_valid) {
         if (view_index.page == current_page ||
             view_index.page == transition.target_page) {
           x_offset += transition.progress * page_width * dir;
         }
@@ skipping 998 matching lines @@
 
 void AppsGridView::SetAsFolderDroppingTarget(const Index& target_index,
                                              bool is_target_folder) {
   AppListItemView* target_view =
       static_cast<AppListItemView*>(
           GetViewAtSlotOnCurrentPage(target_index.slot));
   if (target_view)
     target_view->SetAsAttemptedFolderTarget(is_target_folder);
 }
 
-// static
-AppsGridView::ScrollAxis AppsGridView::GetScrollAxis() {
-  // The experimental app list transitions vertically.
-  return app_list::switches::IsExperimentalAppListEnabled()
-             ? SCROLL_AXIS_VERTICAL
-             : SCROLL_AXIS_HORIZONTAL;
-}
-
 }  // namespace app_list