Refactor app list event handling and prerendering.

ContentsView should not be responsible for apps-grid-specific logic.

To this end, moved scroll and gesture event handling from ContentsView
to AppsGridView, removing the special cases for NAMED_PAGE_APPS. Also
moved some of the prerender logic from ContentsView to AppsGridView.

BUG=377381

Review URL: https://codereview.chromium.org/497413003

Cr-Commit-Position: refs/heads/master@{#292591}

4 files changed, 86 insertions, 100 deletions

diff --git a/ui/app_list/views/apps_grid_view.cc b/ui/app_list/views/apps_grid_view.cc
index f150eb6..1605c88 100644
--- a/ui/app_list/views/apps_grid_view.cc
+++ b/ui/app_list/views/apps_grid_view.cc
@@ -92,6 +92,12 @@ const int kFolderItemReparentDelay = 50;
 // 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
@@ -846,11 +852,12 @@ void AppsGridView::SetDragAndDropHostOfCurrentAppList(
   drag_and_drop_host_ = drag_and_drop_host;
 }
 
-void AppsGridView::Prerender(int page_index) {
+void AppsGridView::Prerender() {
   Layout();
-  int start = std::max(0, (page_index - kPrerenderPages) * tiles_per_page());
+  int selected_page = std::max(0, pagination_model_.selected_page());
+  int start = std::max(0, (selected_page - kPrerenderPages) * tiles_per_page());
   int end = std::min(view_model_.view_size(),
-                     (page_index + 1 + kPrerenderPages) * tiles_per_page());
+                     (selected_page + 1 + kPrerenderPages) * tiles_per_page());
   for (int i = start; i < end; i++) {
     AppListItemView* v = static_cast<AppListItemView*>(view_model_.view_at(i));
     v->Prerender();
@@ -953,6 +960,23 @@ bool AppsGridView::OnKeyReleased(const ui::KeyEvent& event) {
   return handled;
 }
 
+bool AppsGridView::OnMouseWheel(const ui::MouseWheelEvent& event) {
+  int offset;
+  if (abs(event.x_offset()) > abs(event.y_offset()))
+    offset = event.x_offset();
+  else
+    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;
+}
+
 void AppsGridView::ViewHierarchyChanged(
     const ViewHierarchyChangedDetails& details) {
   if (!details.is_add && details.parent == this) {
@@ -971,6 +995,57 @@ void AppsGridView::ViewHierarchyChanged(
   }
 }
 
+void AppsGridView::OnGestureEvent(ui::GestureEvent* event) {
+  switch (event->type()) {
+    case ui::ET_GESTURE_SCROLL_BEGIN:
+      pagination_model_.StartScroll();
+      event->SetHandled();
+      return;
+    case ui::ET_GESTURE_SCROLL_UPDATE:
+      // event->details.scroll_x() > 0 means moving contents to right. That is,
+      // transitioning to previous page.
+      pagination_model_.UpdateScroll(event->details().scroll_x() /
+                                     GetContentsBounds().width());
+      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: {
+      pagination_model_.EndScroll(true);
+      if (fabs(event->details().velocity_x()) > kMinHorizVelocityToSwitchPage) {
+        pagination_model_.SelectPageRelative(
+            event->details().velocity_x() < 0 ? 1 : -1, true);
+      }
+      event->SetHandled();
+      return;
+    }
+    default:
+      break;
+  }
+}
+
+void AppsGridView::OnScrollEvent(ui::ScrollEvent* event) {
+  if (event->type() == ui::ET_SCROLL_FLING_CANCEL)
+    return;
+
+  float offset;
+  if (std::abs(event->x_offset()) > std::abs(event->y_offset()))
+    offset = event->x_offset();
+  else
+    offset = event->y_offset();
+
+  if (std::abs(offset) > kMinScrollToSwitchPage) {
+    if (!pagination_model_.has_transition()) {
+      pagination_model_.SelectPageRelative(offset > 0 ? -1 : 1, true);
+    }
+    event->SetHandled();
+    event->StopPropagation();
+  }
+}
+
 void AppsGridView::Update() {
   DCHECK(!selected_view_ && !drag_view_);
   view_model_.Clear();
diff --git a/ui/app_list/views/apps_grid_view.h b/ui/app_list/views/apps_grid_view.h
index 6a94e40..0e470a2 100644
--- a/ui/app_list/views/apps_grid_view.h
+++ b/ui/app_list/views/apps_grid_view.h
@@ -117,8 +117,8 @@ class APP_LIST_EXPORT AppsGridView : public views::View,
   void SetDragAndDropHostOfCurrentAppList(
       ApplicationDragAndDropHost* drag_and_drop_host);
 
-  // Prerenders the icons on and around |page_index|.
-  void Prerender(int page_index);
+  // Prerenders the icons on and around the currently selected page.
+  void Prerender();
 
   // Return true if the |bounds_animator_| is animating |view|.
   bool IsAnimatingView(views::View* view);
@@ -134,6 +134,7 @@ class APP_LIST_EXPORT AppsGridView : public views::View,
   virtual void Layout() OVERRIDE;
   virtual bool OnKeyPressed(const ui::KeyEvent& event) OVERRIDE;
   virtual bool OnKeyReleased(const ui::KeyEvent& event) OVERRIDE;
+  virtual bool OnMouseWheel(const ui::MouseWheelEvent& event) OVERRIDE;
   virtual void ViewHierarchyChanged(
       const ViewHierarchyChangedDetails& details) OVERRIDE;
   virtual bool GetDropFormats(
@@ -142,6 +143,10 @@ class APP_LIST_EXPORT AppsGridView : public views::View,
   virtual bool CanDrop(const OSExchangeData& data) OVERRIDE;
   virtual int OnDragUpdated(const ui::DropTargetEvent& event) OVERRIDE;
 
+  // Overridden from ui::EventHandler:
+  virtual void OnGestureEvent(ui::GestureEvent* event) OVERRIDE;
+  virtual void OnScrollEvent(ui::ScrollEvent* event) OVERRIDE;
+
   // Stops the timer that triggers a page flip during a drag.
   void StopPageFlipTimer();
 
diff --git a/ui/app_list/views/contents_view.cc b/ui/app_list/views/contents_view.cc
index e6ae0a8..86f7e7b5 100644
--- a/ui/app_list/views/contents_view.cc
+++ b/ui/app_list/views/contents_view.cc
@@ -25,16 +25,6 @@
 
 namespace app_list {
 
-namespace {
-
-const int kMinMouseWheelToSwitchPage = 20;
-const int kMinScrollToSwitchPage = 20;
-const int kMinHorizVelocityToSwitchPage = 800;
-
-const double kFinishTransitionThreshold = 0.33;
-
-}  // namespace
-
 ContentsView::ContentsView(AppListMainView* app_list_main_view)
     : search_results_view_(NULL),
       start_page_view_(NULL),
@@ -236,9 +226,7 @@ void ContentsView::ShowFolderContent(AppListFolderItem* item) {
 }
 
 void ContentsView::Prerender() {
-  const int selected_page =
-      std::max(0, GetAppsPaginationModel()->selected_page());
-  apps_container_view_->apps_grid_view()->Prerender(selected_page);
+  apps_container_view_->apps_grid_view()->Prerender();
 }
 
 views::View* ContentsView::GetPageView(int index) {
@@ -303,26 +291,6 @@ bool ContentsView::OnKeyPressed(const ui::KeyEvent& event) {
   return view_model_->view_at(GetActivePageIndex())->OnKeyPressed(event);
 }
 
-bool ContentsView::OnMouseWheel(const ui::MouseWheelEvent& event) {
-  if (!IsNamedPageActive(NAMED_PAGE_APPS))
-    return false;
-
-  int offset;
-  if (abs(event.x_offset()) > abs(event.y_offset()))
-    offset = event.x_offset();
-  else
-    offset = event.y_offset();
-
-  if (abs(offset) > kMinMouseWheelToSwitchPage) {
-    if (!GetAppsPaginationModel()->has_transition()) {
-      GetAppsPaginationModel()->SelectPageRelative(offset > 0 ? -1 : 1, true);
-    }
-    return true;
-  }
-
-  return false;
-}
-
 void ContentsView::TotalPagesChanged() {
 }
 
@@ -336,61 +304,4 @@ void ContentsView::TransitionChanged() {
   UpdatePageBounds();
 }
 
-void ContentsView::OnGestureEvent(ui::GestureEvent* event) {
-  if (!IsNamedPageActive(NAMED_PAGE_APPS))
-    return;
-
-  switch (event->type()) {
-    case ui::ET_GESTURE_SCROLL_BEGIN:
-      GetAppsPaginationModel()->StartScroll();
-      event->SetHandled();
-      return;
-    case ui::ET_GESTURE_SCROLL_UPDATE:
-      // event->details.scroll_x() > 0 means moving contents to right. That is,
-      // transitioning to previous page.
-      GetAppsPaginationModel()->UpdateScroll(event->details().scroll_x() /
-                                             GetContentsBounds().width());
-      event->SetHandled();
-      return;
-    case ui::ET_GESTURE_SCROLL_END:
-      GetAppsPaginationModel()->EndScroll(
-          GetAppsPaginationModel()->transition().progress <
-          kFinishTransitionThreshold);
-      event->SetHandled();
-      return;
-    case ui::ET_SCROLL_FLING_START: {
-      GetAppsPaginationModel()->EndScroll(true);
-      if (fabs(event->details().velocity_x()) > kMinHorizVelocityToSwitchPage) {
-        GetAppsPaginationModel()->SelectPageRelative(
-            event->details().velocity_x() < 0 ? 1 : -1, true);
-      }
-      event->SetHandled();
-      return;
-    }
-    default:
-      break;
-  }
-}
-
-void ContentsView::OnScrollEvent(ui::ScrollEvent* event) {
-  if (!IsNamedPageActive(NAMED_PAGE_APPS) ||
-      event->type() == ui::ET_SCROLL_FLING_CANCEL) {
-    return;
-  }
-
-  float offset;
-  if (std::abs(event->x_offset()) > std::abs(event->y_offset()))
-    offset = event->x_offset();
-  else
-    offset = event->y_offset();
-
-  if (std::abs(offset) > kMinScrollToSwitchPage) {
-    if (!GetAppsPaginationModel()->has_transition()) {
-      GetAppsPaginationModel()->SelectPageRelative(offset > 0 ? -1 : 1, true);
-    }
-    event->SetHandled();
-    event->StopPropagation();
-  }
-}
-
 }  // namespace app_list
diff --git a/ui/app_list/views/contents_view.h b/ui/app_list/views/contents_view.h
index b828490..17ecf93 100644
--- a/ui/app_list/views/contents_view.h
+++ b/ui/app_list/views/contents_view.h
@@ -103,7 +103,6 @@ class APP_LIST_EXPORT ContentsView : public 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;
@@ -143,10 +142,6 @@ class APP_LIST_EXPORT ContentsView : public views::View,
   // launcher-page pagination.
   PaginationModel* GetAppsPaginationModel();
 
-  // Overridden from ui::EventHandler:
-  virtual void OnGestureEvent(ui::GestureEvent* event) OVERRIDE;
-  virtual void OnScrollEvent(ui::ScrollEvent* event) OVERRIDE;
-
   // Special sub views of the ContentsView. All owned by the views hierarchy.
   AppsContainerView* apps_container_view_;
   SearchResultListView* search_results_view_;