a11y: Exclude children of nested keyboard accessible controls from a11y tree.

ui/views/widget/native_widget_mac_accessibility_unittest.mm

 // Copyright 2016 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 <memory>
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/mac/mac_util.h"
 #import "base/mac/sdk_forward_declarations.h"
+#include "base/strings/string16.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #import "testing/gtest_mac.h"
 #include "ui/accessibility/ax_enums.h"
 #include "ui/accessibility/ax_node_data.h"
 #import "ui/accessibility/platform/ax_platform_node_mac.h"
 #include "ui/base/ime/text_input_type.h"
 #import "ui/gfx/mac/coordinate_conversion.h"
+#include "ui/views/controls/button/label_button.h"
 #include "ui/views/controls/label.h"
 #include "ui/views/controls/textfield/textfield.h"
 #include "ui/views/test/widget_test.h"
 #include "ui/views/widget/widget.h"
 
 // Expose some methods from AXPlatformNodeCocoa for testing purposes only.
 @interface AXPlatformNodeCocoa (Testing)
 - (NSString*)AXRole;
 @end
 
@@ skipping 30 matching lines @@
     return false;
   }
 
  private:
   ui::AXRole role_;
   bool mouse_was_pressed_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(FlexibleRoleTestView);
 };
 
+class TestLabelButton : public LabelButton {
+ public:
+  TestLabelButton() : LabelButton(nullptr, base::string16()) {
+    // Make sure the label doesn't cover the hit test co-ordinates.
+    label()->SetSize(gfx::Size(1, 1));
+  }
+
+  using LabelButton::label;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TestLabelButton);
+};
+
 class NativeWidgetMacAccessibilityTest : public test::WidgetTest {
  public:
   NativeWidgetMacAccessibilityTest() {}
 
   void SetUp() override {
     test::WidgetTest::SetUp();
     widget_ = CreateTopLevelPlatformWidget();
     widget_->SetBounds(gfx::Rect(50, 50, 100, 100));
     widget()->Show();
   }
@@ skipping 28 matching lines @@
   gfx::Rect GetWidgetBounds() { return widget_->GetClientAreaBoundsInScreen(); }
 
  private:
   Widget* widget_ = nullptr;
 
   DISALLOW_COPY_AND_ASSIGN(NativeWidgetMacAccessibilityTest);
 };
 
 }  // namespace
 
+// Check that potentially keyboard-focusable elements are always leaf nodes.
+TEST_F(NativeWidgetMacAccessibilityTest, FocusableElementsAreLeafNodes) {
+  // LabelButtons will have a label inside the button. The label should be
+  // ignored because the button is potentially keyboard focusable.
+  TestLabelButton* button = new TestLabelButton();
+  button->SetSize(widget()->GetContentsView()->size());
+  widget()->GetContentsView()->AddChildView(button);
+  EXPECT_NSEQ(NSAccessibilityButtonRole,
+              AttributeValueAtMidpoint(NSAccessibilityRoleAttribute));
+  EXPECT_EQ(
+      0u,
+      [[button->GetNativeViewAccessible()
+          accessibilityAttributeValue:NSAccessibilityChildrenAttribute] count]);
+
+  // The exception is if the child is explicitly marked accessibility focusable.
+  button->label()->SetFocusBehavior(View::FocusBehavior::ACCESSIBLE_ONLY);
+  EXPECT_EQ(
+      1u,
+      [[button->GetNativeViewAccessible()
+          accessibilityAttributeValue:NSAccessibilityChildrenAttribute] count]);
+  EXPECT_EQ(button->label()->GetNativeViewAccessible(),
+            [[button->GetNativeViewAccessible()
+                accessibilityAttributeValue:NSAccessibilityChildrenAttribute]
+                objectAtIndex:0]);
+
+  // If the child is disabled, it should still be traversable.
+  button->label()->SetEnabled(false);
+  EXPECT_EQ(
+      1u,
+      [[button->GetNativeViewAccessible()
+          accessibilityAttributeValue:NSAccessibilityChildrenAttribute] count]);
+  EXPECT_EQ(button->label()->GetNativeViewAccessible(),
+            [[button->GetNativeViewAccessible()
+                accessibilityAttributeValue:NSAccessibilityChildrenAttribute]
+                objectAtIndex:0]);
+}
+
 // Test for NSAccessibilityChildrenAttribute, and ensure it excludes ignored
 // children from the accessibility tree.
 TEST_F(NativeWidgetMacAccessibilityTest, ChildrenAttribute) {
   // Check childless views don't have accessibility children.
   EXPECT_EQ(0u,
             [AttributeValueAtMidpoint(NSAccessibilityChildrenAttribute) count]);
 
   const size_t kNumChildren = 3;
   for (size_t i = 0; i < kNumChildren; ++i) {
     // Make sure the labels won't interfere with the hit test.
@@ skipping 386 matching lines @@
 
   for (NSString* attribute_name in expected_unsupported_attributes) {
     SCOPED_TRACE(base::SysNSStringToUTF8([NSString
         stringWithFormat:@"Missing attribute is: %@", attribute_name]));
     EXPECT_FALSE([views_attributes containsObject:attribute_name]);
     EXPECT_FALSE([cocoa_attributes containsObject:attribute_name]);
   }
 }
 
 }  // namespace views