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

ui/views/widget/native_widget_mac_accessibility_unittest.mm

Index: ui/views/widget/native_widget_mac_accessibility_unittest.mm
diff --git a/ui/views/widget/native_widget_mac_accessibility_unittest.mm b/ui/views/widget/native_widget_mac_accessibility_unittest.mm
index 3d641d190f9eab41fa0d4a97d726766736902263..24a9def68b8e6e039be69aeea926cbbbe8bd5bf3 100644
--- a/ui/views/widget/native_widget_mac_accessibility_unittest.mm
+++ b/ui/views/widget/native_widget_mac_accessibility_unittest.mm
@@ -14,6 +14,7 @@
 #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"
@@ -102,6 +103,47 @@ class NativeWidgetMacAccessibilityTest : public test::WidgetTest {
 
 }  // 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.
+  LabelButton* button =
+      new LabelButton(nullptr, base::SysNSStringToUTF16(kTestStringValue));
+  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.

[tapted, 2016/11/29 03:12:49]

it seems odd to say this but to not call SetFocusBehavior. Can we do the test
without adding a second LabelButton. I think you just need to copy-paste the
`TestLabelButton` from label_button_unittest.cc (it's small enough to not bother
putting it in its own header). Then you can call SetFocusBehavior on the label
inside the button itself.

[Patti Lor, 2016/11/29 23:26:18]

Done.

+  LabelButton* child_button = new LabelButton(nullptr, base::string16());
+  // Make sure it's size 0 so we can hit test |button|.
+  child_button->SetSize(gfx::Size());

[tapted, 2016/11/29 03:12:49]

Is there an neat alternative to setting the size to zero? This is OK too, but
the concern is that someone why decide to change `IsDrawn` to incorporate
whether the view has zero size as well..

[Patti Lor, 2016/11/29 23:26:18]

Not sure, I think we could potentially use SetBoundsRect() and set the origin
not-inside |button_| (like, to 0, 0 relative to screen coords, or something)?
Not sure if that's very nice though. I've changed it to a 1x1 size now, let me
know if you want that reverted.

[tapted, 2016/11/29 23:43:20]

yeah - I like this better. thanks.

[Patti Lor, 2016/11/30 05:13:25]

Updated the comment to reflect the new size too - forgot to do that.

+  button->AddChildView(child_button);
+  EXPECT_EQ(
+      1u,
+      [[button->GetNativeViewAccessible()
+          accessibilityAttributeValue:NSAccessibilityChildrenAttribute] count]);
+  EXPECT_EQ(child_button->GetNativeViewAccessible(),
+            [[button->GetNativeViewAccessible()
+                accessibilityAttributeValue:NSAccessibilityChildrenAttribute]
+                objectAtIndex:0]);
+
+  // If the child is disabled, it should still work.

[tapted, 2016/11/29 03:12:49]

nit: work -> be traversable?

[Patti Lor, 2016/11/29 23:26:18]

Done.

+  child_button->SetEnabled(false);
+  EXPECT_EQ(
+      1u,
+      [[button->GetNativeViewAccessible()
+          accessibilityAttributeValue:NSAccessibilityChildrenAttribute] count]);
+  EXPECT_EQ(child_button->GetNativeViewAccessible(),
+            [[button->GetNativeViewAccessible()
+                accessibilityAttributeValue:NSAccessibilityChildrenAttribute]
+                objectAtIndex:0]);
+}
+
 // Test for NSAccessibilityChildrenAttribute, and ensure it excludes ignored
 // children from the accessibility tree.
 TEST_F(NativeWidgetMacAccessibilityTest, ChildrenAttribute) {