Rework app list item drag zones.

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>
 
@@ skipping 76 matching lines @@
 const int kFolderDroppingDelay = 150;
 
 // 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;
+const int kFolderDroppingCircleRadius = 39;
 
 // 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,
@@ skipping 74 matching lines @@
   virtual void AnimationCanceled(const gfx::Animation* animation) OVERRIDE {
     view_->SchedulePaint();
   }
 
  private:
   views::View* view_;
 
   DISALLOW_COPY_AND_ASSIGN(ItemMoveAnimationDelegate);
 };
 
-// Gets the distance between the centers of the |rect_1| and |rect_2|.
-int GetDistanceBetweenRects(gfx::Rect rect_1,
-                            gfx::Rect rect_2) {
-  return (rect_1.CenterPoint() - rect_2.CenterPoint()).Length();
-}
-
 // Returns true if the |item| is an folder item.
 bool IsFolderItem(AppListItem* item) {
   return (item->GetItemType() == AppListFolderItem::kItemType);
 }
 
 bool IsOEMFolderItem(AppListItem* item) {
   return IsFolderItem(item) &&
          (static_cast<AppListFolderItem*>(item))->folder_type() ==
              AppListFolderItem::FOLDER_TYPE_OEM;
 }
 
+int ClampToRange(int value, int min, int max) {
+  return std::min(std::max(value, min), max);
+}
+
 }  // namespace
 
 #if defined(OS_WIN)
 // Interprets drag events sent from Windows via the drag/drop API and forwards
 // them to AppsGridView.
 // On Windows, in order to have the OS perform the drag properly we need to
 // provide it with a shortcut file which may or may not exist at the time the
 // drag is started. Therefore while waiting for that shortcut to be located we
 // just do a regular "internal" drag and transition into the synchronous drag
 // when the shortcut is found/created. Hence a synchronous drag is an optional
@@ skipping 262 matching lines @@
                                 Pointer pointer,
                                 const ui::LocatedEvent& event) {
   DCHECK(view);
   if (drag_view_ || pulsing_blocks_model_.view_size())
     return;
 
   drag_view_ = view;
   drag_view_init_index_ = GetIndexOfView(drag_view_);
   drag_view_offset_ = event.location();
   drag_start_page_ = pagination_model_.selected_page();
+  reorder_placeholder_ = GetIndexOfView(drag_view_);
   ExtractDragLocation(event, &drag_start_grid_view_);
   drag_view_start_ = gfx::Point(drag_view_->x(), drag_view_->y());
 }
 
 void AppsGridView::StartSettingUpSynchronousDrag() {
 #if defined(OS_WIN)
   if (!delegate_ || !use_synchronous_drag_)
     return;
 
   // Folders and downloading items can't be integrated with the OS.
@@ skipping 107 matching lines @@
       return;
 
     StartSettingUpSynchronousDrag();
     if (!dragging_for_reparent_item_)
       StartDragAndDropHostDrag(point);
   }
 
   if (drag_pointer_ != pointer)
     return;
 
+  drag_view_->SetPosition(drag_view_start_ + drag_vector);
+
   last_drag_point_ = point;
   const Index last_reorder_drop_target = reorder_drop_target_;
   const Index last_folder_drop_target = folder_drop_target_;
   DropAttempt last_drop_attempt = drop_attempt_;
-  CalculateDropTarget(last_drag_point_, false);
+  CalculateDropTarget();
 
-  if (IsPointWithinDragBuffer(last_drag_point_))
-    MaybeStartPageFlipTimer(last_drag_point_);
-  else
-    StopPageFlipTimer();
+  MaybeStartPageFlipTimer(last_drag_point_);
 
   if (page_switcher_view_) {
     gfx::Point page_switcher_point(last_drag_point_);
     views::View::ConvertPointToTarget(
         this, page_switcher_view_, &page_switcher_point);
     page_switcher_view_->UpdateUIForDragPoint(page_switcher_point);
   }
 
-  if (!EnableFolderDragDropUI()) {
-    if (last_reorder_drop_target != reorder_drop_target_)
-      AnimateToIdealBounds();
-    drag_view_->SetPosition(drag_view_start_ + drag_vector);
-    return;
-  }
-
-  // Update drag with folder UI enabled.
   if (last_folder_drop_target != folder_drop_target_ ||
       last_reorder_drop_target != reorder_drop_target_ ||
       last_drop_attempt != drop_attempt_) {
     if (drop_attempt_ == DROP_FOR_REORDER) {
       folder_dropping_timer_.Stop();
       reorder_timer_.Start(FROM_HERE,
           base::TimeDelta::FromMilliseconds(kReorderDelay),
           this, &AppsGridView::OnReorderTimer);
     } else if (drop_attempt_ == DROP_FOR_FOLDER) {
       reorder_timer_.Stop();
       folder_dropping_timer_.Start(FROM_HERE,
           base::TimeDelta::FromMilliseconds(kFolderDroppingDelay),
           this, &AppsGridView::OnFolderDroppingTimer);
     }
 
     // Reset the previous drop target.
     SetAsFolderDroppingTarget(last_folder_drop_target, false);
   }
-
-  drag_view_->SetPosition(drag_view_start_ + drag_vector);
 }
 
 void AppsGridView::EndDrag(bool cancel) {
   // EndDrag was called before if |drag_view_| is NULL.
   if (!drag_view_)
     return;
 
   // Coming here a drag and drop was in progress.
   bool landed_in_drag_and_drop_host = forward_events_to_drag_and_drop_host_;
   if (forward_events_to_drag_and_drop_host_) {
@@ skipping 18 matching lines @@
     if (IsDraggingForReparentInRootLevelGridView()) {
       // An EndDrag can be received during a reparent via a model change. This
       // is always a cancel and needs to be forwarded to the folder.
       DCHECK(cancel);
       delegate_->CancelDragInActiveFolder();
       return;
     }
 
     if (!cancel && dragging()) {
       // Regular drag ending path, ie, not for reparenting.
-      CalculateDropTarget(last_drag_point_, true);
+      CalculateDropTarget();
       if (EnableFolderDragDropUI() && drop_attempt_ == DROP_FOR_FOLDER &&
           IsValidIndex(folder_drop_target_)) {
         MoveItemToFolder(drag_view_, folder_drop_target_);
       } else if (IsValidIndex(reorder_drop_target_)) {
         MoveItemInModel(drag_view_, reorder_drop_target_);
       }
     }
   }
 
   if (drag_and_drop_host_) {
@@ skipping 64 matching lines @@
   layer()->SetOpacity(show ? 1.0f : 0.0f);
 }
 
 void AppsGridView::InitiateDragFromReparentItemInRootLevelGridView(
     AppListItemView* original_drag_view,
     const gfx::Rect& drag_view_rect,
     const gfx::Point& drag_point) {
   DCHECK(original_drag_view && !drag_view_);
   DCHECK(!dragging_for_reparent_item_);
 
+  // Since the item is new, its placeholder is conceptually at the back of the
+  // entire apps grid.
+  reorder_placeholder_ = GetLastViewIndex();
+
   // Create a new AppListItemView to duplicate the original_drag_view in the
   // folder's grid view.
   AppListItemView* view = new AppListItemView(this, original_drag_view->item());
   AddChildView(view);
   drag_view_ = view;
   drag_view_->SetPaintToLayer(true);
   // Note: For testing purpose, SetFillsBoundsOpaquely can be set to true to
   // show the gray background.
   drag_view_->SetFillsBoundsOpaquely(false);
   drag_view_->SetBoundsRect(drag_view_rect);
@@ skipping 29 matching lines @@
 
 bool AppsGridView::IsDraggedView(const views::View* view) const {
   return drag_view_ == view;
 }
 
 void AppsGridView::ClearDragState() {
   drop_attempt_ = DROP_FOR_NONE;
   drag_pointer_ = NONE;
   reorder_drop_target_ = Index();
   folder_drop_target_ = Index();
+  reorder_placeholder_ = Index();
   drag_start_grid_view_ = gfx::Point();
   drag_start_page_ = -1;
   drag_view_offset_ = gfx::Point();
 
   if (drag_view_) {
     drag_view_->OnDragEnded();
     if (IsDraggingForReparentInRootLevelGridView()) {
       const int drag_view_index = view_model_.GetIndexOfView(drag_view_);
       CHECK_EQ(view_model_.view_size() - 1, drag_view_index);
       DeleteItemViewAtIndex(drag_view_index);
@@ skipping 262 matching lines @@
 }
 
 views::View* AppsGridView::GetViewAtIndex(const Index& index) const {
   if (!IsValidIndex(index))
     return NULL;
 
   const int model_index = GetModelIndexFromIndex(index);
   return view_model_.view_at(model_index);
 }
 
+AppsGridView::Index AppsGridView::GetLastViewIndex() const {
+  DCHECK_LT(0, view_model_.view_size());
+  int view_index = view_model_.view_size() - 1;
+  return Index(view_index / tiles_per_page(), view_index % tiles_per_page());
+}
+
 void AppsGridView::MoveSelected(int page_delta,
                                 int slot_x_delta,
                                 int slot_y_delta) {
   if (!selected_view_)
     return SetSelectedItemByIndex(Index(pagination_model_.selected_page(), 0));
 
   const Index& selected = GetIndexOfView(selected_view_);
   int target_slot = selected.slot + slot_x_delta + slot_y_delta * cols_;
 
   if (selected.slot % cols_ == 0 && slot_x_delta == -1) {
@@ skipping 43 matching lines @@
       pagination_model_.transition();
   const bool is_valid = pagination_model_.is_valid_page(transition.target_page);
 
   // Transition to previous page means negative offset.
   const int dir = transition.target_page > current_page ? -1 : 1;
 
   const int total_views =
       view_model_.view_size() + pulsing_blocks_model_.view_size();
   int slot_index = 0;
   for (int i = 0; i < total_views; ++i) {
-    if (i < view_model_.view_size() && view_model_.view_at(i) == drag_view_) {
-      if (EnableFolderDragDropUI() && drop_attempt_ == DROP_FOR_FOLDER)
-        ++slot_index;
+    if (i < view_model_.view_size() && view_model_.view_at(i) == drag_view_)
       continue;
-    }
 
     Index view_index = GetIndexFromModelIndex(slot_index);
 
-    // Leaves a blank space in the grid for the current reorder drop target.
-    if (reorder_drop_target_ == view_index &&
-        drop_attempt_ == DROP_FOR_REORDER) {
+    // Leaves a blank space in the grid for the current reorder placeholder.
+    if (reorder_placeholder_ == view_index) {
       ++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 (pagination_controller_->scroll_axis() ==
         PaginationController::SCROLL_AXIS_HORIZONTAL) {
@@ skipping 132 matching lines @@
   views::View::ConvertPointFromWidget(this, drag_point);
 #else
   // For non-aura, root location is not clearly defined but |drag_view_| does
   // not have the scale transform. So no round error would be introduced and
   // it's okay to use View::ConvertPointToTarget.
   *drag_point = event.location();
   views::View::ConvertPointToTarget(drag_view_, this, drag_point);
 #endif
 }
 
-void AppsGridView::CalculateDropTarget(const gfx::Point& drag_point,
-                                       bool use_page_button_hovering) {
-  if (EnableFolderDragDropUI()) {
-    CalculateDropTargetWithFolderEnabled(drag_point, use_page_button_hovering);
+void AppsGridView::CalculateDropTarget() {
+  DCHECK(drag_view_);
+
+  gfx::Point point = drag_view_->icon()->bounds().CenterPoint();
+  views::View::ConvertPointToTarget(drag_view_, this, &point);
+  if (!IsPointWithinDragBuffer(point)) {
+    // Reset the reorder target to the original position if the cursor is
+    // outside the drag buffer.
+    if (IsDraggingForReparentInRootLevelGridView()) {
+      drop_attempt_ = DROP_FOR_NONE;
+      return;
+    }
+
+    reorder_drop_target_ = drag_view_init_index_;
+    drop_attempt_ = DROP_FOR_REORDER;
+    return;
+  }
+
+  if (EnableFolderDragDropUI() &&
+      CalculateFolderDropTarget(point, &folder_drop_target_)) {
+    drop_attempt_ = DROP_FOR_FOLDER;
     return;
   }
 
   drop_attempt_ = DROP_FOR_REORDER;
+  CalculateReorderDropTarget(point, &reorder_drop_target_);
+}

[tapted, 2014/09/15 06:12:53]

neat!

[calamity, 2014/09/15 06:36:15]

Acknowledged.

 
-  int current_page = pagination_model_.selected_page();
-  gfx::Point point(drag_point);
-  if (!IsPointWithinDragBuffer(drag_point)) {
-    point = drag_start_grid_view_;
-    current_page = drag_start_page_;
+bool AppsGridView::CalculateFolderDropTarget(const gfx::Point& point,
+                                             Index* drop_target) {

[tapted, 2014/09/15 06:12:53]

It would be nice if these functions were const. But you'll need to sweep through
and ensure GetExpectedTileBounds, CanDropIntoTarget, etc. are all const too.
There might be a dealbreaker along the way though, in which case (if it's not
const) the drop_target argument is probably unwarranted. (I find it pretty
readable with that though, so up to you if you want to keep it)

rationale: AppsGridView is pretty epic and hard to reason about. `const` will
help a bit. Basically all the Can* and Get* functions should be const. Also at
the back of my mind is that all the DragState-related stuff could move to some
kind of `DragHelper` class (the `ResetDragState` function is kindof a giveaway
that such a thing should exist to encapsulate that). But that's all a bit
orthogonal.

[calamity, 2014/09/15 06:36:15]

Well. That was a lot easier than I thought it would be.

+  Index nearest_tile_index(GetNearestTileIndexForPoint(point));
+  int distance_to_tile_center =
+      (point - GetExpectedTileBounds(nearest_tile_index.slot).CenterPoint())
+          .Length();
+  if (nearest_tile_index != reorder_placeholder_ &&
+      distance_to_tile_center < kFolderDroppingCircleRadius &&
+      !IsFolderItem(drag_view_->item()) &&
+      CanDropIntoTarget(nearest_tile_index)) {
+    *drop_target = nearest_tile_index;
+    return true;
   }
 
-  if (use_page_button_hovering && page_switcher_view_ &&
-      page_switcher_view_->bounds().Contains(point)) {
-    gfx::Point page_switcher_point(point);
-    views::View::ConvertPointToTarget(this, page_switcher_view_,
-                                      &page_switcher_point);
-    int page = page_switcher_view_->GetPageForPoint(page_switcher_point);
-    if (pagination_model_.is_valid_page(page)) {
-      reorder_drop_target_.page = page;
-      reorder_drop_target_.slot = tiles_per_page() - 1;
-    }
+  return false;
+}
+
+void AppsGridView::CalculateReorderDropTarget(const gfx::Point& point,
+                                              Index* drop_target) {
+  gfx::Rect bounds = GetContentsBounds();
+  Index grid_index = GetNearestTileIndexForPoint(point);
+  gfx::Point reorder_placeholder_center =
+      GetExpectedTileBounds(reorder_placeholder_.slot).CenterPoint();
+
+  int column_offset_direction = 0;
+  if (grid_index == reorder_placeholder_) {
+    column_offset_direction =
+        reorder_placeholder_center.x() < point.x() ? -1 : 1;
   } else {
-    gfx::Rect bounds(GetContentsBounds());
-    const int drop_row = (point.y() - bounds.y()) / kPreferredTileHeight;
-    const int drop_col = std::min(cols_ - 1,
-        (point.x() - bounds.x()) / kPreferredTileWidth);
-
-    reorder_drop_target_.page = current_page;
-    reorder_drop_target_.slot = std::max(
-        0, std::min(tiles_per_page() - 1, drop_row * cols_ + drop_col));
+    column_offset_direction = reorder_placeholder_ < grid_index ? -1 : 1;
   }
 
-  // Limits to the last possible slot on last page.
-  if (reorder_drop_target_.page == pagination_model_.total_pages() - 1) {
-    reorder_drop_target_.slot =
-        std::min((view_model_.view_size() - 1) % tiles_per_page(),
-                 reorder_drop_target_.slot);
+  int row = grid_index.slot / cols_;
+
+  // Offset the target column based on the direction of the target. This will
+  // result in earlier targets getting their reorder zone shifted backwards
+  // and later targets getting their reorder zones shifted forwards.
+  //
+  // This makes eordering feel like the user is slotting items into the spaces
+  // between apps.
+  int column_offset = column_offset_direction *

[tapted, 2014/09/15 06:12:53]

nit: maybe a _px or _pixels suffix? Or even just `x_offset`. currently seems a
bit too much like it should be offsetting the column index.

[calamity, 2014/09/15 06:36:15]

Done.

+                      (kPreferredTileWidth - kFolderDroppingCircleRadius) / 2;
+  int col = (point.x() - bounds.x() + column_offset) / kPreferredTileWidth;
+  col = ClampToRange(col, 0, cols_ - 1);
+  reorder_drop_target_ =
+      std::min(Index(pagination_model_.selected_page(), row * cols_ + col),
+               GetLastViewIndex());

[tapted, 2014/09/15 06:12:53]

nice

+}
+
+void AppsGridView::OnReorderTimer() {
+  if (drop_attempt_ == DROP_FOR_REORDER) {
+    reorder_placeholder_ = reorder_drop_target_;
+    AnimateToIdealBounds();
   }
 }
 
-
-void AppsGridView::CalculateDropTargetWithFolderEnabled(
-    const gfx::Point& drag_point,
-    bool use_page_button_hovering) {
-  gfx::Point point(drag_point);
-  if (!IsPointWithinDragBuffer(drag_point)) {
-    point = drag_start_grid_view_;
-  }
-
-  if (use_page_button_hovering && page_switcher_view_ &&
-      page_switcher_view_->bounds().Contains(point)) {
-    gfx::Point page_switcher_point(point);
-    views::View::ConvertPointToTarget(this, page_switcher_view_,
-                                      &page_switcher_point);
-    int page = page_switcher_view_->GetPageForPoint(page_switcher_point);
-    if (pagination_model_.is_valid_page(page))
-      drop_attempt_ = DROP_FOR_NONE;
-  } else {
-    DCHECK(drag_view_);
-    // Try to find the nearest target for folder dropping or re-ordering.
-    CalculateNearestTileForDragView();
-  }
-}
-
-void AppsGridView::OnReorderTimer() {
-  if (drop_attempt_ == DROP_FOR_REORDER)
-    AnimateToIdealBounds();
-}
-
 void AppsGridView::OnFolderItemReparentTimer() {
   DCHECK(folder_delegate_);
   if (drag_out_of_folder_container_ && drag_view_) {
     folder_delegate_->ReparentItem(drag_view_, last_drag_point_);
 
     // Set the flag in the folder's grid view.
     dragging_for_reparent_item_ = true;
 
     // Do not observe any data change since it is going to be hidden.
     item_list_->RemoveObserver(this);
@@ skipping 78 matching lines @@
 void AppsGridView::EndDragFromReparentItemInRootLevel(
     bool events_forwarded_to_drag_drop_host,
     bool cancel_drag) {
   // EndDrag was called before if |drag_view_| is NULL.
   if (!drag_view_)
     return;
 
   DCHECK(IsDraggingForReparentInRootLevelGridView());
   bool cancel_reparent = cancel_drag || drop_attempt_ == DROP_FOR_NONE;
   if (!events_forwarded_to_drag_drop_host && !cancel_reparent) {
-    CalculateDropTarget(last_drag_point_, true);
+    CalculateDropTarget();
     if (drop_attempt_ == DROP_FOR_REORDER &&
         IsValidIndex(reorder_drop_target_)) {
       ReparentItemForReorder(drag_view_, reorder_drop_target_);
     } else if (drop_attempt_ == DROP_FOR_FOLDER &&
                IsValidIndex(folder_drop_target_)) {
       ReparentItemToAnotherFolder(drag_view_, folder_drop_target_);
     }
     SetViewHidden(drag_view_, false /* show */, true /* no animate */);
   }
 
@@ skipping 465 matching lines @@
 
   UpdatePaging();
   AnimateToIdealBounds();
 }
 
 void AppsGridView::TotalPagesChanged() {
 }
 
 void AppsGridView::SelectedPageChanged(int old_selected, int new_selected) {
   if (dragging()) {
-    CalculateDropTarget(last_drag_point_, true);
+    CalculateDropTarget();
     Layout();
     MaybeStartPageFlipTimer(last_drag_point_);
   } else {
     ClearSelectedView(selected_view_);
     Layout();
   }
 }
 
 void AppsGridView::TransitionStarted() {
   CancelContextMenusOnCurrentPage();
@@ skipping 22 matching lines @@
   view->layer()->SetOpacity(hide ? 0 : 1);
 }
 
 void AppsGridView::OnImplicitAnimationsCompleted() {
   if (layer()->opacity() == 0.0f)
     SetVisible(false);
 }
 
 bool AppsGridView::EnableFolderDragDropUI() {
   // Enable drag and drop folder UI only if it is at the app list root level
-  // and the switch is on and the target folder can still accept new items.
-  return model_->folders_enabled() && !folder_delegate_ &&
-         CanDropIntoTarget(folder_drop_target_);
+  // and the switch is on.
+  return model_->folders_enabled() && !folder_delegate_;
 }
 
 bool AppsGridView::CanDropIntoTarget(const Index& drop_target) {
-  views::View* target_view = GetViewAtSlotOnCurrentPage(drop_target.slot);
+  views::View* target_view = GetViewAtIndex(drop_target);
   if (!target_view)
-    return true;
+    return false;
 
   AppListItem* target_item =
       static_cast<AppListItemView*>(target_view)->item();
   // Items can be dropped into non-folders (which have no children) or folders
   // that have fewer than the max allowed items.
   // OEM folder does not allow to drag/drop other items in it.
   return target_item->ChildItemCount() < kMaxFolderItems &&
          !IsOEMFolderItem(target_item);
 }
 
-// TODO(jennyz): Optimize the calculation for finding nearest tile.
-void AppsGridView::CalculateNearestTileForDragView() {
-  Index nearest_tile;
-  nearest_tile.page = -1;
-  nearest_tile.slot = -1;
-  int d_min = -1;
-
-  // Calculate the top left tile |drag_view| intersects.
-  gfx::Point pt = drag_view_->bounds().origin();
-  CalculateNearestTileForVertex(pt, &nearest_tile, &d_min);
-
-  // Calculate the top right tile |drag_view| intersects.
-  pt = drag_view_->bounds().top_right();
-  CalculateNearestTileForVertex(pt, &nearest_tile, &d_min);
-
-  // Calculate the bottom left tile |drag_view| intersects.
-  pt = drag_view_->bounds().bottom_left();
-  CalculateNearestTileForVertex(pt, &nearest_tile, &d_min);
-
-  // Calculate the bottom right tile |drag_view| intersects.
-  pt = drag_view_->bounds().bottom_right();
-  CalculateNearestTileForVertex(pt, &nearest_tile, &d_min);
-
-  const int d_folder_dropping =
-      kFolderDroppingCircleRadius + kGridIconDimension / 2;
-  const int d_reorder = kReorderDroppingCircleRadius + kGridIconDimension / 2;
-
-  // If user drags an item across pages to the last page, and targets it
-  // to the last empty slot on it, push the last item for re-ordering.
-  if (IsLastPossibleDropTarget(nearest_tile) && d_min < d_reorder) {
-    drop_attempt_ = DROP_FOR_REORDER;
-    nearest_tile.slot = nearest_tile.slot - 1;
-    reorder_drop_target_ = nearest_tile;
-    return;
-  }
-
-  if (IsValidIndex(nearest_tile)) {
-    if (d_min < d_folder_dropping) {
-      views::View* target_view = GetViewAtSlotOnCurrentPage(nearest_tile.slot);
-      if (target_view &&
-          !IsFolderItem(static_cast<AppListItemView*>(drag_view_)->item())) {
-        // If a non-folder item is dragged to the target slot with an item
-        // sitting on it, attempt to drop the dragged item into the folder
-        // containing the item on nearest_tile.
-        drop_attempt_ = DROP_FOR_FOLDER;
-        folder_drop_target_ = nearest_tile;
-        return;
-      } else {
-        // If the target slot is blank, or the dragged item is a folder, attempt
-        // to re-order.
-        drop_attempt_ = DROP_FOR_REORDER;
-        reorder_drop_target_ = nearest_tile;
-        return;
-      }
-    } else if (d_min < d_reorder) {
-      // Entering the re-order circle of the slot.
-      drop_attempt_ = DROP_FOR_REORDER;
-      reorder_drop_target_ = nearest_tile;
-      return;
-    }
-  }
-
-  // If |drag_view| is not entering the re-order or folder dropping region of
-  // any items, cancel any previous re-order or folder dropping timer.
-  drop_attempt_ = DROP_FOR_NONE;
-  reorder_timer_.Stop();
-  folder_dropping_timer_.Stop();
-
-  // When dragging for reparent a folder item, it should go back to its parent
-  // folder item if there is no drop target.
-  if (IsDraggingForReparentInRootLevelGridView()) {
-    DCHECK(activated_folder_item_view_);
-    folder_drop_target_ = GetIndexOfView(activated_folder_item_view_);
-  }
-}
-
-void AppsGridView::CalculateNearestTileForVertex(const gfx::Point& vertex,
-                                                 Index* nearest_tile,
-                                                 int* d_min) {
-  Index target_index;
-  gfx::Rect target_bounds = GetTileBoundsForPoint(vertex, &target_index);
-
-  if (target_bounds.IsEmpty() || target_index == *nearest_tile)
-    return;
-
-  // Do not count the tile, where drag_view_ used to sit on and is still moving
-  // on top of it, in calculating nearest tile for drag_view_.
-  views::View* target_view = GetViewAtSlotOnCurrentPage(target_index.slot);
-  if (target_index == drag_view_init_index_ && !target_view &&
-      !IsDraggingForReparentInRootLevelGridView()) {
-    return;
-  }
-
-  int d_center = GetDistanceBetweenRects(drag_view_->bounds(), target_bounds);
-  if (*d_min < 0 || d_center < *d_min) {
-    *d_min = d_center;
-    *nearest_tile = target_index;
-  }
-}
-
-gfx::Rect AppsGridView::GetTileBoundsForPoint(const gfx::Point& point,
-                                              Index *tile_index) {
-  // Check if |point| is outside of contents bounds.
-  gfx::Rect bounds(GetContentsBounds());
-  if (!bounds.Contains(point))
-    return gfx::Rect();
-
-  // Calculate which tile |point| is enclosed in.
-  int x = point.x();
-  int y = point.y();
-  int col = (x - bounds.x()) / kPreferredTileWidth;
-  int row = (y - bounds.y()) / kPreferredTileHeight;
-  gfx::Rect tile_rect = GetExpectedTileBounds(row, col);
-
-  // Check if |point| is outside a valid item's tile.
-  Index index(pagination_model_.selected_page(), row * cols_ + col);
-  *tile_index = index;
-  return tile_rect;
+AppsGridView::Index AppsGridView::GetNearestTileIndexForPoint(
+    const gfx::Point& point) const {
+  gfx::Rect bounds = GetContentsBounds();
+  int col =
+      ClampToRange((point.x() - bounds.x()) / kPreferredTileWidth, 0, cols_);
+  int row = ClampToRange(
+      (point.y() - bounds.y()) / kPreferredTileHeight, 0, rows_per_page_);
+  return Index(pagination_model_.selected_page(), row * cols_ + col);
 }
 
 gfx::Size AppsGridView::GetTileGridSize() const {
   gfx::Rect bounds = GetExpectedTileBounds(0, 0);
   bounds.Union(GetExpectedTileBounds(rows_per_page_ - 1, cols_ - 1));
   return bounds.size();
 }
 
+gfx::Rect AppsGridView::GetExpectedTileBounds(int slot) const {
+  return GetExpectedTileBounds(slot / cols_, slot % cols_);
+}
+
 gfx::Rect AppsGridView::GetExpectedTileBounds(int row, int col) const {
   gfx::Rect bounds(GetContentsBounds());
   gfx::Size tile_size(kPreferredTileWidth, kPreferredTileHeight);
   return gfx::Rect(gfx::Point(bounds.x() + col * tile_size.width(),
                               bounds.y() + row * tile_size.height()),
                    tile_size);
 }
 
-bool AppsGridView::IsLastPossibleDropTarget(const Index& index) const {
-  int last_possible_slot = view_model_.view_size() % tiles_per_page();
-  return (index.page == pagination_model_.total_pages() - 1 &&
-          index.slot == last_possible_slot + 1);
-}
-
 views::View* AppsGridView::GetViewAtSlotOnCurrentPage(int slot) {
   if (slot < 0)
     return NULL;
 
   // Calculate the original bound of the tile at |index|.
   int row = slot / cols_;
   int col = slot % cols_;
   gfx::Rect tile_rect = GetExpectedTileBounds(row, col);
 
   for (int i = 0; i < view_model_.view_size(); ++i) {
     views::View* view = view_model_.view_at(i);
     if (view->bounds() == tile_rect && view != drag_view_)
       return view;
   }
   return NULL;
 }
 
 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);
 }
 
 }  // namespace app_list