MacViews a11y: Sync VoiceOver cursor with keyboard focus.

ui/views/cocoa/bridged_content_view.mm

Index: ui/views/cocoa/bridged_content_view.mm
diff --git a/ui/views/cocoa/bridged_content_view.mm b/ui/views/cocoa/bridged_content_view.mm
index 1623e32b8ede82ff2b578ad5500010dca09f991c..41e0ac4cf3dfa7f6abc262cb8fd39a0b2fbe16ff 100644
--- a/ui/views/cocoa/bridged_content_view.mm
+++ b/ui/views/cocoa/bridged_content_view.mm
@@ -25,6 +25,7 @@
 #include "ui/gfx/path.h"
 #import "ui/gfx/path_mac.h"
 #include "ui/gfx/scoped_ns_graphics_context_save_gstate_mac.h"
+#include "ui/views/accessibility/native_view_accessibility.h"
 #import "ui/views/cocoa/bridged_native_widget.h"
 #import "ui/views/cocoa/drag_drop_client_mac.h"
 #include "ui/views/controls/menu/menu_config.h"
@@ -1362,4 +1363,10 @@ ui::KeyEvent GetCharacterEventFromNSEvent(NSEvent* event) {
   return [hostedView_->GetNativeViewAccessible() accessibilityHitTest:point];
 }
 
+- (id)accessibilityFocusedUIElement {
+  if (!hostedView_)
+    return nil;
+  return hostedView_->GetNativeViewAccessibility()->GetFocus();

[tapted, 2016/09/28 01:03:20]

What about 

`return [hostedView_->GetNativeViewAccessibility()
accessibilityFocusedUIElement];`

and implementing - (id)accessibilityFocusedUIElement; in ax_platform_node_mac.mm
-- I think one of the objectives is that both BridgedNativeWidget and
AXPlatformNodeCocoa have a fully-fleshed-out implementation of the
NSAccessibility protocol.

I think one problem is that

NativeViewHostMac::GetNativeViewAccessible() 

probably won't actually have a views::NativeViewAccessibility to return.

In fact, GetNativeViewAccessible() currently returns NULL -- it can probably
return |native_view_|, on the assumption that the hosted view (probably a
RenderWidgetHostViewCocoa) implements the NSAccessiblity protocol. Which it
does, so the above suggestion should allow BridgedContentView to invoke the
accessibilityFocusedUIElement in render_widget_host_view_mac.mm

(maybe this is even a clue to the outstanding TODO?)

[dmazzoni, 2016/09/29 16:06:15]

Another alternative, this is the preferred method that I had in mind:

First get hostedView_->GetNativeViewAccessible().

Then use AXPlatformNode::FromNativeViewAccessible, which
will succeed if the NSAccessibility is backed by an AXPlatformNode.

Then AXPlatformNode::delegate()->GetFocus(), which is implemented
by NativeViewAccessibility in this specific case, but you don't have to
assume that.

Let me know if that will work.

Right now this might seem slightly roundabout because every
AXPlatformNode is backed by a NativeViewAccessibility, so why not
just cut out the middleman? My eventual goal is that the web accessibility
classes will eventually inherit from AXPlatformNodeDelegate, so 99% of
the accessible objects will all be implemented by AXPlatformNode, but
some will be views and some will be web.

[Patti Lor, 2016/10/04 05:45:14]

dmazzoni@: I don't think that will work - as far as I can tell, the definition
for non-Windows calls to FromNativeViewAccessible() just returns a nullptr (see
https://cs.chromium.org/chromium/src/ui/accessibility/platform/ax_platform_no...).
I went ahead and tried anyway just to double check, and it seems there's a
couple of other things required too, like making FromNativeViewAccessible public
(it's protected) and fixing a linker error for
ui::AXPlatformNode::FromNativeViewAccessible not being found. That's as far as I
got, because I wasn't sure if these were also intended consequences of your
suggestion - let me know.

tapted@: Have gone with your change for patchset 4, but it doesn't seem to make
a difference with drawing the cursor in the right place. The NativeViewHostMac
|native_view_| member variable always seems to be null, including when
traversing focus inside the web content area.

+}
+
 @end