Allow pages on the OSX app launcher to be turned while dragging.

ui/app_list/cocoa/apps_grid_controller.mm

 // Copyright 2013 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.
 
 #import "ui/app_list/cocoa/apps_grid_controller.h"
 
 #include "base/mac/foundation_util.h"
 #include "ui/app_list/app_list_model.h"
 #include "ui/app_list/app_list_model_observer.h"
 #include "ui/app_list/app_list_view_delegate.h"
@@ skipping 15 matching lines @@
 
 // Preferred tile size when showing in fixed layout. These should be even
 // numbers to ensure that if they are grown 50% they remain integers.
 const CGFloat kPreferredTileWidth = 88;
 const CGFloat kPreferredTileHeight = 98;
 
 const CGFloat kViewWidth =
     kFixedColumns * kPreferredTileWidth + 2 * kLeftRightPadding;
 const CGFloat kViewHeight = kFixedRows * kPreferredTileHeight;
 
+const NSTimeInterval kScrollWhileDraggingDelay = 1.0;
 NSTimeInterval g_scroll_duration = 0.18;
 
 }  // namespace
 
 @interface AppsGridController ()
 
+- (void)scrollToPageWithTimer:(size_t)targetPage;
+- (void)onTimer:(NSTimer*)theTimer;
+
 // Cancel a currently running scroll animation.
 - (void)cancelScrollAnimation;
 
 // Index of the page with the most content currently visible.
 - (size_t)nearestPageIndex;
 
 // Bootstrap the views this class controls.
 - (void)loadAndSetView;
 
 - (void)boundsDidChange:(NSNotification*)notification;
@@ skipping 186 matching lines @@
     [[self collectionViewAtPageIndex:visiblePage_]
         setSelectionIndexes:[NSIndexSet indexSet]];
   }
 
   newOrigin.x = pageIndex * kViewWidth;
   [NSAnimationContext beginGrouping];
   [[NSAnimationContext currentContext] setDuration:g_scroll_duration];
   [[clipView animator] setBoundsOrigin:newOrigin];
   [NSAnimationContext endGrouping];
   animatingScroll_ = YES;
+  targetScrollPage_ = pageIndex;
+  [self cancelScrollTimer];
+}
+
+- (void)maybeChangePageForPoint:(NSPoint)locationInWindow {
+  NSPoint pointInView = [[self view] convertPoint:locationInWindow
+                                         fromView:nil];
+  // Check if the point is outside the view on the left or right.
+  if (pointInView.x <= 0 || pointInView.x >= NSWidth([[self view] bounds])) {
+    size_t targetPage = visiblePage_;
+    if (pointInView.x <= 0)
+      targetPage -= targetPage != 0 ? 1 : 0;
+    else
+      targetPage += targetPage < [pages_ count] - 1 ? 1 : 0;
+    [self scrollToPageWithTimer:targetPage];
+    return;
+  }
+
+  if (paginationObserver_) {
+    NSInteger segment =
+        [paginationObserver_ pagerSegmentAtLocation:locationInWindow];
+    if (segment >= 0 && static_cast<size_t>(segment) != targetScrollPage_) {
+      [self scrollToPageWithTimer:segment];
+      return;
+    }
+  }
+
+  // Otherwise the point may have moved back into the view.
+  [self cancelScrollTimer];
+}
+
+- (void)cancelScrollTimer {
+  scheduledScrollPage_ = targetScrollPage_;
+  [scrollWhileDraggingTimer_ invalidate];
+}
+
+- (void)scrollToPageWithTimer:(size_t)targetPage {
+  if (targetPage == targetScrollPage_) {
+    [self cancelScrollTimer];
+    return;
+  }
+
+  if (targetPage == scheduledScrollPage_)
+    return;
+
+  scheduledScrollPage_ = targetPage;
+  [scrollWhileDraggingTimer_ invalidate];
+  scrollWhileDraggingTimer_.reset(
+      [[NSTimer scheduledTimerWithTimeInterval:kScrollWhileDraggingDelay
+                                        target:self
+                                      selector:@selector(onTimer:)
+                                      userInfo:nil
+                                       repeats:NO] retain]);
+}
+
+- (void)onTimer:(NSTimer*)theTimer {
+  if (scheduledScrollPage_ == targetScrollPage_)
+    return;  // Already animating scroll.
+
+  [self scrollToPage:scheduledScrollPage_];
 }
 
 - (void)cancelScrollAnimation {
   NSClipView* clipView = [[self gridScrollView] contentView];
   [NSAnimationContext beginGrouping];
   [[NSAnimationContext currentContext] setDuration:0];
   [[clipView animator] setBoundsOrigin:[clipView bounds].origin];
   [NSAnimationContext endGrouping];
   animatingScroll_ = NO;
 }
@@ skipping 203 matching lines @@
 
   model_->apps()->RemoveObserver(bridge_.get());
   model_->apps()->Move(itemIndex, modelIndex);
   model_->apps()->AddObserver(bridge_.get());
 }
 
 - (AppsCollectionViewDragManager*)dragManager {
   return dragManager_;
 }
 
+- (size_t)scheduledScrollPage {
+  return scheduledScrollPage_;
+}
+
 - (void)listItemsAdded:(size_t)start
                  count:(size_t)count {
   // Cancel any drag, to ensure the model stays consistent.
   [dragManager_ cancelDrag];
 
   for (size_t i = start; i < start + count; ++i) {
     app_list::AppListItemModel* itemModel = model_->apps()->GetItemAt(i);
     [items_ insertObject:[NSValue valueWithPointer:itemModel]
                  atIndex:i];
   }
@@ skipping 97 matching lines @@
     return [self moveSelectionByDelta:-kItemsPerPage];
 
   if (command == @selector(pageDown:) ||
       command == @selector(scrollPageDown:))
     return [self moveSelectionByDelta:kItemsPerPage];
 
   return NO;
 }
 
 @end