TableView: Re-implement accessibility support for Screen Readers

Currently TableView constructs the virtual accessibility views by
clearing and creating the entire accessibility tree for every
action (Creating, Adding, Removing, Sorting, Adding Columns, etc).
This introduces a few major problems with screen readers.

For example in UIA supported readers, the TableView is not accessible
at all, when the virtual accessibility views are being destroyed and
created, the narrator looses its context causing the focus to shift to
the parent, causing a flicker like effect and the user cannot announce
any cells. For IAccessible2 supported readers, for low end devices, it
takes time to construct all the virtual accessibility views causing
some cells to not narrate.

So instead of destroying and re-creating all the virtual accessibility
views every time there is a change to the table model or the sorting,
it will add, remove and re-arrange virtual accessibility views on an
individual basis.

and other tables in Chromium's UI.

Bug: 1078623
Change-Id: Ie2de53b4460fed87843b6ce81e90a24194b04c2a
AX-Relnotes: UIA screen readers, such as Narrator, announce all information in the Task Manager
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2379091
Commit-Queue: Mohamed Mansour <mmansour@microsoft.com>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Nektarios Paisios <nektar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813489}

ui/views/accessibility/view_accessibility.cc

@@ -59,7 +59,16 @@ ViewAccessibility::~ViewAccessibility() = default;
 
 void ViewAccessibility::AddVirtualChildView(
     std::unique_ptr<AXVirtualView> virtual_view) {
+  AddVirtualChildViewAt(std::move(virtual_view), int{virtual_children_.size()});
+}
+
+void ViewAccessibility::AddVirtualChildViewAt(
+    std::unique_ptr<AXVirtualView> virtual_view,
+    int index) {
   DCHECK(virtual_view);
+  DCHECK_GE(index, 0);
+  DCHECK_LE(size_t{index}, virtual_children_.size());
+
   if (virtual_view->parent_view() == this)
     return;
   DCHECK(!virtual_view->parent_view()) << "This |view| already has a View "
@@ -69,7 +78,8 @@ void ViewAccessibility::AddVirtualChildView(
                                                   "AXVirtualView parent. Call "
                                                   "RemoveChildView first.";
   virtual_view->set_parent_view(this);
-  virtual_children_.push_back(std::move(virtual_view));
+  auto insert_iterator = virtual_children_.begin() + index;
+  virtual_children_.insert(insert_iterator, std::move(virtual_view));
 }
 
 std::unique_ptr<AXVirtualView> ViewAccessibility::RemoveVirtualChildView(

ui/views/accessibility/view_accessibility.h

@@ -119,6 +119,11 @@ class VIEWS_EXPORT ViewAccessibility {
   // virtual children.
   void AddVirtualChildView(std::unique_ptr<AXVirtualView> virtual_view);
 
+  // Adds |virtual_view| as a child of this View at an index.
+  // We take ownership of our virtual children.
+  void AddVirtualChildViewAt(std::unique_ptr<AXVirtualView> virtual_view,
+                             int index);
+
   // Removes |virtual_view| from this View. The virtual view's parent will
   // change to nullptr. Hands ownership back to the caller.
   std::unique_ptr<AXVirtualView> RemoveVirtualChildView(

ui/views/accessibility/view_ax_platform_node_delegate_unittest.cc

@@ -434,11 +434,11 @@ class DerivedTestView : public View {
   void OnBlur() override { SetVisible(false); }
 };
 
-using ViewAccessibilityTest = ViewsTestBase;
+using AXViewTest = ViewsTestBase;
 
 // Check if the destruction of the widget ends successfully if |view|'s
 // visibility changed during destruction.
-TEST_F(ViewAccessibilityTest, LayoutCalledInvalidateRootView) {
+TEST_F(AXViewTest, LayoutCalledInvalidateRootView) {
   // TODO(jamescook): Construct a real AutomationManagerAura rather than using
   // this observer to simulate it.
   AXAuraObjCache cache;

ui/views/controls/table/table_view.h

@@ -49,7 +49,7 @@ class TableHeader;
 class TableViewObserver;
 class TableViewTestHelper;
 
-// The cells in the first column of a table can contain:
+// The cell's in the first column of a table can contain:
 // - only text
 // - a small icon (16x16) and some text
 // - a check box and some text
@@ -206,10 +206,13 @@ class VIEWS_EXPORT TableView : public views::View,
   bool GetSortOnPaint() const;
   void SetSortOnPaint(bool sort_on_paint);
 
+  // Returns the proper ax sort direction.
+  ax::mojom::SortDirection GetFirstSortDescriptorDirection() const;
+
   TableTypes GetTableType() const;
 
   // Updates the relative bounds of the virtual accessibility children created
-  // in UpdateVirtualAccessibilityChildren(). This function is public so that
+  // in RebuildVirtualAccessibilityChildren(). This function is public so that
   // the table's |header_| can trigger an update when its visible bounds are
   // changed, because its accessibility information is also contained in the
   // table's virtual accessibility children.
@@ -248,7 +251,7 @@ class VIEWS_EXPORT TableView : public views::View,
   struct GroupSortHelper;
   struct SortHelper;
 
-  // Used during painting to determine the range of cells that need to be
+  // Used during painting to determine the range of cell's that need to be
   // painted.
   // NOTE: the row indices returned by this are in terms of the view and column
   // indices in terms of |visible_columns_|.
@@ -272,9 +275,6 @@ class VIEWS_EXPORT TableView : public views::View,
   // in a cell.
   int GetCellElementSpacing() const;
 
-  // Invoked when the number of rows changes in some way.
-  void NumRowsChanged();
-
   // Does the actual sort and updates the mappings (|view_to_model_| and
   // |model_to_view_|) appropriately. If |schedule_paint| is true,
   // schedules a paint. This should be true, unless called from
@@ -308,7 +308,7 @@ class VIEWS_EXPORT TableView : public views::View,
   // Updates the |x| and |width| of each of the columns in |visible_columns_|.
   void UpdateVisibleColumnSizes();
 
-  // Returns the cells that need to be painted for the specified region.
+  // Returns the cell's that need to be painted for the specified region.
   // |bounds| is in terms of |this|.
   PaintRegion GetPaintRegion(const gfx::Rect& bounds) const;
 
@@ -353,17 +353,17 @@ class VIEWS_EXPORT TableView : public views::View,
 
   // Updates a set of accessibility views that expose the visible table contents
   // to assistive software.
-  void UpdateVirtualAccessibilityChildren();
+  void RebuildVirtualAccessibilityChildren();
 
   // Clears the set of accessibility views set up in
-  // UpdateVirtualAccessibilityChildren(). Useful when the model is in the
+  // RebuildVirtualAccessibilityChildren(). Useful when the model is in the
   // process of changing but the virtual accessibility children haven't been
   // updated yet, e.g. showing or hiding a column via SetColumnVisibility().
   void ClearVirtualAccessibilityChildren();
 
   // Helper functions used in UpdateVirtualAccessibilityChildrenBounds() for
   // calculating the accessibility bounds for the header and table rows and
-  // cells.
+  // cell's.
   gfx::Rect CalculateHeaderRowAccessibilityBounds() const;
   gfx::Rect CalculateHeaderCellAccessibilityBounds(
       const int visible_column_index) const;
@@ -386,6 +386,37 @@ class VIEWS_EXPORT TableView : public views::View,
   // |visible_column_index| indexes into |visible_columns_|.
   AXVirtualView* GetVirtualAccessibilityCell(int row, int visible_column_index);
 
+  // Creates a virtual accessibility view that is used to expose information
+  // about the row at |view_index| to assistive software.
+  std::unique_ptr<AXVirtualView> CreateRowAccessibilityView(int view_index);
+
+  // Creates a virtual accessibility view that is used to expose information
+  // about the cell at the provided coordinates |row_index| and |column_index|
+  // to assistive software.
+  std::unique_ptr<AXVirtualView> CreateCellAccessibilityView(
+      int row_index,
+      size_t column_index);
+
+  // Creates a virtual accessibility view that is used to expose information
+  // about this header to assistive software.
+  std::unique_ptr<AXVirtualView> CreateHeaderAccessibilityView();
+
+  // Updates the accessibility data for |ax_row| to match the data in the view
+  // at |view_index| in the table. Returns false if row data not changed.
+  bool UpdateVirtualAccessibilityRowData(AXVirtualView* ax_row,
+                                         int view_index,
+                                         int model_index);
+
+  // The accessibility view |ax_row| callback function that populates the
+  // accessibility data for a table row.
+  void PopulateAccessibilityRowData(AXVirtualView* ax_row,
+                                    ui::AXNodeData* data);
+
+  // The accessibility view |ax_cell| callback function that populates the
+  // accessibility data for a table cell.
+  void PopulateAccessibilityCellData(AXVirtualView* ax_cell,
+                                     ui::AXNodeData* data);
+
   ui::TableModel* model_ = nullptr;
 
   std::vector<ui::TableColumn> columns_;