Modify screen reader detection to use the AXEnhancedUserInterface attribute set on AXApplication when VoiceOver's turned on. This gives us the ability to turn on ax even after a render widget host has started.

BUG=none
TEST=manually with VoiceOver.  Launch Chrome, VoiceOver, windows, tabs (permuted order) and verify that ax is on.  This sometimes required navigation to a different page or efreshing the current page.
Review URL: http://codereview.chromium.org/6909013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@83940 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 26 insertions, 18 deletions

diff --git a/chrome/browser/accessibility/browser_accessibility_state.h b/chrome/browser/accessibility/browser_accessibility_state.h
index bdd7bcc..65d6b42 100644
--- a/chrome/browser/accessibility/browser_accessibility_state.h
+++ b/chrome/browser/accessibility/browser_accessibility_state.h
@@ -22,8 +22,11 @@ template <typename T> struct DefaultSingletonTraits;
 // we attempt to dynamically detect a MSAA client screen reader by calling
 // NotifiyWinEvent in WidgetWin with a custom ID and wait to see if the ID
 // is requested by a subsequent call to WM_GETOBJECT.
-// (2) On mac we detect if VoiceOver is running. This is stored in a preference
-// file for Universal Access with the key "voiceOverOnOffKey".
+// (2) On mac we detect dynamically if VoiceOver is running.  We rely upon the
+// undocumented accessibility attribute @"AXEnhancedUserInterface" which is set
+// when VoiceOver is launched and unset when VoiceOver is closed.  This is an
+// improvement over reading defaults preference values (which has no callback
+// mechanism).
 class BrowserAccessibilityState {
  public:
   // Returns the singleton instance.
diff --git a/chrome/browser/chrome_browser_application_mac.mm b/chrome/browser/chrome_browser_application_mac.mm
index 7ba8cda..745e0ab 100644
--- a/chrome/browser/chrome_browser_application_mac.mm
+++ b/chrome/browser/chrome_browser_application_mac.mm
@@ -9,9 +9,13 @@
 #import "base/memory/scoped_nsobject.h"
 #import "base/sys_string_conversions.h"
 #import "chrome/app/breakpad_mac.h"
+#include "chrome/browser/accessibility/browser_accessibility_state.h"
 #import "chrome/browser/app_controller_mac.h"
+#include "chrome/browser/ui/browser_list.h"
 #import "chrome/browser/ui/cocoa/objc_method_swizzle.h"
 #import "chrome/browser/ui/cocoa/objc_zombie.h"
+#include "chrome/browser/ui/tab_contents/tab_contents_wrapper.h"
+#include "content/browser/renderer_host/render_view_host.h"
 
 // The implementation of NSExceptions break various assumptions in the
 // Chrome code.  This category defines a replacement for
@@ -384,4 +388,21 @@ BOOL SwizzleNSExceptionInit() {
   [super reportException:anException];
 }
 
+- (void)accessibilitySetValue:(id)value forAttribute:(NSString*)attribute {
+  if ([attribute isEqualToString:@"AXEnhancedUserInterface"] &&
+      [value intValue] == 1) {
+    BrowserAccessibilityState::GetInstance()->OnScreenReaderDetected();
+    for (TabContentsIterator it;
+         !it.done();
+         ++it) {
+      if (TabContentsWrapper* contents = *it) {
+        if (RenderViewHost* rvh = contents->render_view_host()) {
+          rvh->EnableRendererAccessibility();
+        }
+      }
+    }
+  }
+  return [super accessibilitySetValue:value forAttribute:attribute];
+}
+
 @end
diff --git a/chrome/browser/renderer_host/render_widget_host_view_mac.h b/chrome/browser/renderer_host/render_widget_host_view_mac.h
index dc06563..d2a3f33c 100644
--- a/chrome/browser/renderer_host/render_widget_host_view_mac.h
+++ b/chrome/browser/renderer_host/render_widget_host_view_mac.h
@@ -354,9 +354,6 @@ class RenderWidgetHostViewMac : public RenderWidgetHostView {
   // invoke it from the message loop.
   void ShutdownHost();
 
-  // Used to determine whether or not to enable accessibility.
-  bool IsVoiceOverRunning();
-
   // The associated view. This is weak and is inserted into the view hierarchy
   // to own this RenderWidgetHostViewMac object.
   RenderWidgetHostViewCocoa* cocoa_view_;
diff --git a/chrome/browser/renderer_host/render_widget_host_view_mac.mm b/chrome/browser/renderer_host/render_widget_host_view_mac.mm
index 2b2d785..7eb5631 100644
--- a/chrome/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/chrome/browser/renderer_host/render_widget_host_view_mac.mm
@@ -16,7 +16,6 @@
 #include "base/sys_info.h"
 #include "base/sys_string_conversions.h"
 #import "chrome/browser/accessibility/browser_accessibility_cocoa.h"
-#include "chrome/browser/accessibility/browser_accessibility_state.h"
 #include "chrome/browser/browser_trial.h"
 #import "chrome/browser/renderer_host/text_input_client_mac.h"
 #include "chrome/browser/spellchecker_platform_engine.h"
@@ -642,12 +641,6 @@ RenderWidgetHostViewMac::RenderWidgetHostViewMac(RenderWidgetHost* widget)
                   initWithRenderWidgetHostViewMac:this] autorelease];
   render_widget_host_->set_view(this);
 
-  // Turn on accessibility only if VoiceOver is running.
-  if (IsVoiceOverRunning()) {
-    BrowserAccessibilityState::GetInstance()->OnScreenReaderDetected();
-    render_widget_host_->EnableRendererAccessibility();
-  }
-
   if (render_widget_host_->IsRenderView()) {
     new SpellCheckRenderViewObserver(
         static_cast<RenderViewHost*>(widget), this);
@@ -1346,12 +1339,6 @@ void RenderWidgetHostViewMac::ShutdownHost() {
   // Do not touch any members at this point, |this| has been deleted.
 }
 
-bool RenderWidgetHostViewMac::IsVoiceOverRunning() {
-  NSUserDefaults* user_defaults = [NSUserDefaults standardUserDefaults];
-  [user_defaults addSuiteNamed:@"com.apple.universalaccess"];
-  return 1 == [user_defaults integerForKey:@"voiceOverOnOffKey"];
-}
-
 gfx::Rect RenderWidgetHostViewMac::GetViewCocoaBounds() const {
   return gfx::Rect(NSRectToCGRect([cocoa_view_ bounds]));
 }