a11y: Add a11y information to views::Tab and manually ignore its a11y children.

ui/views/controls/tabbed_pane/tabbed_pane.cc

 // Copyright (c) 2012 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.
 
 #include "ui/views/controls/tabbed_pane/tabbed_pane.h"
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "third_party/skia/include/core/SkPaint.h"
 #include "third_party/skia/include/core/SkPath.h"
+#include "ui/accessibility/ax_action_data.h"
 #include "ui/accessibility/ax_node_data.h"
 #include "ui/base/default_style.h"
 #include "ui/base/material_design/material_design_controller.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/events/keycodes/keyboard_codes.h"
 #include "ui/gfx/animation/animation_delegate.h"
 #include "ui/gfx/animation/linear_animation.h"
 #include "ui/gfx/animation/tween.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/font_list.h"
 #include "ui/native_theme/native_theme.h"
 #include "ui/views/border.h"
 #include "ui/views/controls/label.h"
 #include "ui/views/controls/tabbed_pane/tabbed_pane_listener.h"
 #include "ui/views/layout/box_layout.h"
 #include "ui/views/layout/fill_layout.h"
 #include "ui/views/layout/layout_manager.h"
 #include "ui/views/widget/widget.h"
 
+namespace views {
+
 namespace {
 
 // TODO(markusheintz|msw): Use NativeTheme colors.
 const SkColor kTabTitleColor_Inactive = SkColorSetRGB(0x64, 0x64, 0x64);
 const SkColor kTabTitleColor_Active = SK_ColorBLACK;
 const SkColor kTabTitleColor_Hovered = SK_ColorBLACK;
 const SkColor kTabBorderColor = SkColorSetRGB(0xC8, 0xC8, 0xC8);
 const SkScalar kTabBorderThickness = 1.0f;
 
 const gfx::Font::Weight kHoverWeight = gfx::Font::Weight::NORMAL;
 const gfx::Font::Weight kActiveWeight = gfx::Font::Weight::BOLD;
 const gfx::Font::Weight kInactiveWeight = gfx::Font::Weight::NORMAL;
 
 const int kHarmonyTabStripTabHeight = 40;
 
+// views::Tab shouldn't expose any of its children in the a11y tree. Instead, it

[tapted, 2017/01/03 00:29:27]

nit: move comment into GetAccessibleNodeData. the comment here should just be
something like "The View containing the text for each tab in the tab strip."

[Patti Lor, 2017/01/06 02:02:29]

Done.

+// should provide the a11y information itself. Normally, non-keyboard-focusable
+// children of keyboard-focusable parents are ignored, but Tabs only mark the
+// currently selected tab as keyboard-focusable. This means all unselected Tabs
+// expose their children to the a11y tree. To fix, manually ignore the children.
+class TabLabel : public Label {
+ public:
+  TabLabel(const base::string16& tab_title)

[tapted, 2017/01/03 00:29:27]

nit; explicit

[Patti Lor, 2017/01/06 02:02:29]

Done.

+      : Label(tab_title,
+              ui::ResourceBundle::GetSharedInstance().GetFontListWithDelta(
+                  ui::kLabelFontSizeDelta,
+                  gfx::Font::NORMAL,
+                  kActiveWeight)) {}
+
+  void GetAccessibleNodeData(ui::AXNodeData* data) override {

[tapted, 2017/01/03 00:29:27]

nit: // Label:

[Patti Lor, 2017/01/06 02:02:30]

Done.

+    data->role = ui::AX_ROLE_IGNORED;
+  }
+};
+
 }  // namespace
 
-namespace views {
-
 // static
 const char TabbedPane::kViewClassName[] = "TabbedPane";
 
 // A subclass of Tab that implements the Harmony visual styling.
 class MdTab : public Tab {
  public:
   MdTab(TabbedPane* tabbed_pane, const base::string16& title, View* contents);
   ~MdTab() override;
 
   // Overridden from Tab:
@@ skipping 66 matching lines @@
   gfx::Range animating_to_;
 
   DISALLOW_COPY_AND_ASSIGN(MdTabStrip);
 };
 
 // static
 const char Tab::kViewClassName[] = "Tab";
 
 Tab::Tab(TabbedPane* tabbed_pane, const base::string16& title, View* contents)
     : tabbed_pane_(tabbed_pane),
-      title_(new Label(
-          title,
-          ui::ResourceBundle::GetSharedInstance().GetFontListWithDelta(
-              ui::kLabelFontSizeDelta,
-              gfx::Font::NORMAL,
-              kActiveWeight))),
+      title_(new TabLabel(title)),
       tab_state_(TAB_ACTIVE),
       contents_(contents) {
   // Calculate this now while the font list is guaranteed to be bold.
   preferred_title_size_ = title_->GetPreferredSize();
 
   const int kTabVerticalPadding = 5;
   const int kTabHorizontalPadding = 10;
 
   SetBorder(CreateEmptyBorder(
       gfx::Insets(kTabVerticalPadding, kTabHorizontalPadding)));
@@ skipping 80 matching lines @@
 }
 
 void Tab::SetState(TabState tab_state) {
   if (tab_state == tab_state_)
     return;
   tab_state_ = tab_state;
   OnStateChanged();
   SchedulePaint();
 }
 
+void Tab::GetAccessibleNodeData(ui::AXNodeData* data) {
+  data->role = ui::AX_ROLE_TAB;
+  data->SetName(title()->text());
+  data->AddStateFlag(ui::AX_STATE_SELECTABLE);
+  if (selected())
+    data->AddStateFlag(ui::AX_STATE_SELECTED);
+}
+
+bool Tab::HandleAccessibleAction(const ui::AXActionData& action_data) {
+  if (action_data.action != ui::AX_ACTION_SET_SELECTION || !enabled())
+    return false;
+  // It's not clear what should happen if a tab is 'deselected', so having the
+  // AX_ACTION_SET_SELECTION action always selects the tab.
+  if (!selected())

[tapted, 2017/01/03 00:29:27]

Can we just ignore requests to SET_SELECTION to 0/false? Then I would remove
this check (just call SelectTab(this).

The hpothetical risk is that if we have Tab(0) selected, something might decide
to do a sequence like: Select(Tab(1)) && Unselect(Tab(0))

[Patti Lor, 2017/01/06 02:02:30]

Yep - so on Mac, I've done this by reporting selected tabs's AXValue as
'uneditable', so as long as the a11y client respects that the "if" here won't be
needed. I mostly just left that in there kinda "just in case". Have deleted it
now.

+    tabbed_pane_->SelectTab(this);
+  return true;
+}
+
 void Tab::OnFocus() {
   OnStateChanged();
   // When the tab gains focus, send an accessibility event indicating that the
   // contents are focused. When the tab loses focus, whichever new View ends up
   // with focus will send an AX_EVENT_FOCUS of its own, so there's no need to
   // send one in OnBlur().
   if (contents())
     contents()->NotifyAccessibilityEvent(ui::AX_EVENT_FOCUS, true);
   SchedulePaint();
 }
@@ skipping 368 matching lines @@
 
 View* TabbedPane::GetSelectedTabContentView() {
   return GetSelectedTab() ? GetSelectedTab()->contents() : nullptr;
 }
 
 void TabbedPane::GetAccessibleNodeData(ui::AXNodeData* node_data) {
   node_data->role = ui::AX_ROLE_TAB_LIST;
 }
 
 }  // namespace views