Experimental app list: Change transition animations of top-level pages.

ui/app_list/views/contents_view.cc

Index: ui/app_list/views/contents_view.cc
diff --git a/ui/app_list/views/contents_view.cc b/ui/app_list/views/contents_view.cc
index 19c9dd93836895343e2c8637f186e69053dbf31e..f0c8dc1aefdc891f8410f4ef27513473e9d8f226 100644
--- a/ui/app_list/views/contents_view.cc
+++ b/ui/app_list/views/contents_view.cc
@@ -118,11 +118,17 @@ int ContentsView::GetActivePageIndex() const {
 }
 
 bool ContentsView::IsNamedPageActive(NamedPage named_page) const {
+  return IndexIsNamedPage(GetActivePageIndex(), named_page);
+}
+
+bool ContentsView::IndexIsNamedPage(int page_index,
+                                    NamedPage named_page) const {
+  // Find the index of the view corresponding to the given named_page.
   std::map<NamedPage, int>::const_iterator it =
       named_page_to_view_.find(named_page);
   if (it == named_page_to_view_.end())
     return false;
-  return it->second == GetActivePageIndex();
+  return it->second == page_index;
 }
 
 int ContentsView::GetPageIndexForNamedPage(NamedPage named_page) const {
@@ -184,6 +190,15 @@ bool ContentsView::IsShowingSearchResults() const {
              : IsNamedPageActive(NAMED_PAGE_SEARCH_RESULTS);
 }
 
+int ContentsView::PageOrigin(const gfx::Rect& bounds, int page_index) const {

[calamity, 2014/09/10 01:56:40]

This is cleaner without |bounds| and I don't think calling GetContentsBounds()
here every time will have a noticeable performance impact.

[Matt Giuca, 2014/09/10 03:15:30]

Done.

+  // The start page and search page origins are above; all other pages' origins
+  // are below.
+  int page_height = bounds.height();
+  bool origin_above = IndexIsNamedPage(page_index, NAMED_PAGE_START) ||
+                      IndexIsNamedPage(page_index, NAMED_PAGE_SEARCH_RESULTS);
+  return origin_above ? -page_height : page_height;
+}
+
 void ContentsView::UpdatePageBounds() {
   gfx::Rect rect(GetContentsBounds());
   if (rect.IsEmpty())
@@ -203,20 +218,17 @@ void ContentsView::UpdatePageBounds() {
     }
   }
 
-  gfx::Rect incoming_target(rect);
-  gfx::Rect outgoing_target(rect);
-  int dir = target_page > current_page ? -1 : 1;
-
-  // Pages transition vertically.
-  int page_height = rect.height();
-  int transition_offset = progress * page_height * dir;
-
-  outgoing_target.set_y(transition_offset);
-  incoming_target.set_y(dir < 0 ? transition_offset + page_height
-                                : transition_offset - page_height);
-
-  view_model_->view_at(current_page)->SetBoundsRect(outgoing_target);
-  view_model_->view_at(target_page)->SetBoundsRect(incoming_target);
+  // Move |current_page| from 0 to its origin. Move |target_page| from its
+  // origin to 0.
+  gfx::Rect current_page_rect(rect);
+  gfx::Rect target_page_rect(rect);
+  int current_page_origin = PageOrigin(rect, current_page);
+  int target_page_origin = PageOrigin(rect, target_page);
+  current_page_rect.set_y(progress * current_page_origin);
+  target_page_rect.set_y((1 - progress) * target_page_origin);
+
+  view_model_->view_at(current_page)->SetBoundsRect(current_page_rect);
+  view_model_->view_at(target_page)->SetBoundsRect(target_page_rect);
 }
 
 PaginationModel* ContentsView::GetAppsPaginationModel() {