app_list: Improve visual feedback for invalid touch scroll.

ui/app_list/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/apps_grid_view.h"
 
 #include <algorithm>
 
 #include "ui/app_list/app_list_item_view.h"
 #include "ui/app_list/pagination_model.h"
 #include "ui/views/border.h"
 
 namespace {
 
 // Padding space in pixels for fixed layout.
 const int kLeftRightPadding = 20;
 const int kTopPadding = 1;
 
 // Padding space in pixels between pages.
 const int kPagePadding = 40;
 
 // Preferred tile size when showing in fixed layout.
 const int kPreferredTileWidth = 88;
 const int kPreferredTileHeight = 98;
 
 // Max extra column padding space in pixels for invalid page transition.
-const int kMaxExtraColPaddingForInvalidTransition = 80;
+const int kMaxExtraColPaddingForInvalidTransition = 15;
+
+// Extra column padding space in pixels of first column for invalid page
+// transition.
+const int kBaseExtraColPaddingForInvalidTransition = 50;
 
 }  // namespace
 
 namespace app_list {
 
 AppsGridView::AppsGridView(views::ButtonListener* listener,
                            PaginationModel* pagination_model)
     : model_(NULL),
       listener_(listener),
       pagination_model_(pagination_model),
@@ skipping 83 matching lines @@
   const PaginationModel::Transition& transition =
       pagination_model_->transition();
   const bool is_valid =
       pagination_model_->is_valid_page(transition.target_page);
 
   // Transition to right means negative offset.
   const int dir = transition.target_page > current_page ? -1 : 1;
   const int transition_offset = is_valid ?
       transition.progress * page_width * dir :
       transition.progress * kMaxExtraColPaddingForInvalidTransition * dir;
+  const int base_transition_offset = is_valid ? 0 :
+      transition.progress * kBaseExtraColPaddingForInvalidTransition * dir;
 
   const int first_visible_index = current_page * tiles_per_page();
   const int last_visible_index = (current_page + 1) * tiles_per_page() - 1;
   gfx::Rect tile_slot(grid_rect.origin(), tile_size);
   for (int i = 0; i < child_count(); ++i) {
     views::View* view = child_at(i);
 
     // Decides an x_offset for current item.
     int x_offset = 0;
     if (i < first_visible_index)
       x_offset = -page_width;
     else if (i > last_visible_index)
       x_offset = page_width;
 
     int page = i / tiles_per_page();
     if (is_valid) {
       if (page == current_page || page == transition.target_page)
         x_offset += transition_offset;
     } else {
       const int col = i % cols_;
+      x_offset += base_transition_offset;
       if (transition_offset > 0)
-        x_offset += transition_offset * (col + 1);
+        x_offset += transition_offset * col;
       else
-        x_offset += transition_offset * (cols_ - col);
+        x_offset += transition_offset * (cols_ - col - 1);
     }
 
     gfx::Rect adjusted_slot(tile_slot);
     adjusted_slot.Offset(x_offset, 0);
     view->SetBoundsRect(adjusted_slot);
 
     tile_slot.Offset(tile_size.width(), 0);
     if ((i + 1) % tiles_per_page() == 0) {
       tile_slot.set_origin(grid_rect.origin());
     } else if ((i + 1) % cols_ == 0) {
@@ skipping 146 matching lines @@
 
 void AppsGridView::SelectedPageChanged(int old_selected, int new_selected) {
   Layout();
 }
 
 void AppsGridView::TransitionChanged() {
   Layout();
 }
 
 }  // namespace app_list