App list uses PaginationModel to transition between pages.

ui/app_list/views/contents_view.h

Index: ui/app_list/views/contents_view.h
diff --git a/ui/app_list/views/contents_view.h b/ui/app_list/views/contents_view.h
index 0a7bfc5cca48011abd644264cb2801597a2fb4af..751079a7f3c3731e570bf56442e471ee7d9eb8a6 100644
--- a/ui/app_list/views/contents_view.h
+++ b/ui/app_list/views/contents_view.h
@@ -11,6 +11,8 @@
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/app_list/app_list_export.h"
+#include "ui/app_list/pagination_model.h"
+#include "ui/app_list/pagination_model_observer.h"
 #include "ui/views/view.h"
 
 namespace content {
@@ -18,7 +20,6 @@ class WebContents;
 }
 
 namespace views {
-class BoundsAnimator;
 class ViewModel;
 }
 
@@ -40,7 +41,8 @@ class StartPageView;
 // one of which can be active at a given time. ContentsView provides the user
 // interface for switching between launcher pages, and animates the transition
 // between them.
-class APP_LIST_EXPORT ContentsView : public views::View {
+class APP_LIST_EXPORT ContentsView : public views::View,
+                                     public PaginationModelObserver {
  public:
   // Values of this enum denote special launcher pages that require hard-coding.
   // Launcher pages are not required to have a NamedPage enum value.
@@ -70,7 +72,7 @@ class APP_LIST_EXPORT ContentsView : public views::View {
   void SetActivePage(int page_index);
 
   // The index of the currently active launcher page.
-  int active_page_index() const { return active_page_; }
+  int GetActivePageIndex() const;
 
   // True if |named_page| is the current active laucher page.
   bool IsNamedPageActive(NamedPage named_page) const;
@@ -83,18 +85,30 @@ class APP_LIST_EXPORT ContentsView : public views::View {
   AppsContainerView* apps_container_view() { return apps_container_view_; }
   StartPageView* start_page_view() { return start_page_view_; }
 
+  // Ends the current animation abruptly (for use in tests).
+  void FinishCurrentAnimationForTests();
+
   // Overridden from views::View:
   virtual gfx::Size GetPreferredSize() const OVERRIDE;
   virtual void Layout() OVERRIDE;
   virtual bool OnKeyPressed(const ui::KeyEvent& event) OVERRIDE;
   virtual bool OnMouseWheel(const ui::MouseWheelEvent& event) OVERRIDE;
 
+  // Overridden from PaginationModelObserver:
+  virtual void TotalPagesChanged() OVERRIDE;
+  virtual void SelectedPageChanged(int old_selected, int new_selected) OVERRIDE;
+  virtual void TransitionStarted() OVERRIDE;
+  virtual void TransitionChanged() OVERRIDE;
+
  private:
   // Invoked when active view is changed.
   void ActivePageChanged();
 
-  void CalculateIdealBounds();
-  void AnimateToIdealBounds();
+  // Calculates and sets the bounds for the subviews. If |ideal| is true, this
+  // calculates the ideal bounds (for after the current animation completes),
+  // which will be used when Layout() is called; otherwise, calculates the
+  // actual bounds (potentially mid-animation) and directly moves the views.
+  void CalculateAndSetBounds(bool ideal);

[calamity, 2014/06/12 03:05:08]

Doesn't the ideal=true case go against the method name since no bounds are
actually set?

Can we just move the SetViewBoundsToIdealBounds call into CalculateAndSetBounds
and change the argument to |animate| instead?

[Matt Giuca, 2014/06/16 00:59:05]

The implication was that "SetBounds" was non-specific about whether the bounds
being set were ideal or actual, and the Boolean flag clears that up.
I don't see how that would work. Doesn't that mean that if animate=true, we
would be setting the ideal bounds to the partial position during the animation?

[Matt Giuca, 2014/06/16 07:20:28]

OK as discussed, no more ideal bounds. This method always sets the bounds
directly; the argument determines whether it ignores the animation or not. (Also
renamed the method.)

 
   // Adds |view| as a new page to the end of the list of launcher pages. The
   // view is inserted as a child of the ContentsView. There is no name
@@ -107,15 +121,14 @@ class APP_LIST_EXPORT ContentsView : public views::View {
   int AddLauncherPage(views::View* view, NamedPage named_page);
 
   // Gets the PaginationModel owned by the AppsGridView.
+  // Note: This is different to |pagination_model_|, which manages top-level
+  // launcher-page pagination.
   PaginationModel* GetAppsPaginationModel();
 
   // Overridden from ui::EventHandler:
   virtual void OnGestureEvent(ui::GestureEvent* event) OVERRIDE;
   virtual void OnScrollEvent(ui::ScrollEvent* event) OVERRIDE;
 
-  // Index into |view_model_| of the currently active page.
-  int active_page_;
-
   // Special sub views of the ContentsView. All owned by the views hierarchy.
   AppsContainerView* apps_container_view_;
   SearchResultListView* search_results_view_;
@@ -126,7 +139,9 @@ class APP_LIST_EXPORT ContentsView : public views::View {
   scoped_ptr<views::ViewModel> view_model_;
   // Maps NamedPage onto |view_model_| indices.
   std::map<NamedPage, int> named_page_to_view_;
-  scoped_ptr<views::BoundsAnimator> bounds_animator_;
+
+  // Manages the pagination for the launcher pages.
+  PaginationModel pagination_model_;
 
   DISALLOW_COPY_AND_ASSIGN(ContentsView);
 };