Accessibility Mac: Cache Accessible Elements and Notify about changes

The big change is that we now keep the id objects representing accessibles
around so that they are persistent for ATs.
This improves performance of Mac accessibility significantly.

This is required for notifications which are now sent so that many things work much better,
for example the VoiceOver focus follows the keyboard focus.

The parent element in QCocoaAccessibleElement was removed, we can
dynamically access it more reliably.

Change-Id: I686d212f40d28b392dcc22f16f3c3430f08bdc98
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>

1 files changed, 73 insertions, 23 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoaaccessibilityelement.mm b/src/plugins/platforms/cocoa/qcocoaaccessibilityelement.mm
index d9bfdbd55d..1df4230385 100644
--- a/src/plugins/platforms/cocoa/qcocoaaccessibilityelement.mm
+++ b/src/plugins/platforms/cocoa/qcocoaaccessibilityelement.mm
@@ -41,6 +41,8 @@
 #include "qcocoaaccessibilityelement.h"
 #include "qcocoaaccessibility.h"
 #include "qcocoahelpers.h"
+#include "qcocoawindow.h"
+#include "private/qaccessiblecache_p.h"
 
 #include <QtGui/qaccessible.h>
 
@@ -48,7 +50,7 @@
 
 @implementation QCocoaAccessibleElement
 
-- (id)initWithId:(QAccessible::Id)anId parent:(id)aParent
+- (id)initWithId:(QAccessible::Id)anId
 {
     Q_ASSERT((int)anId < 0);
     self = [super init];
@@ -57,15 +59,35 @@
         QAccessibleInterface *iface = QAccessible::accessibleInterface(axid);
         Q_ASSERT(iface);
         role = QCocoaAccessible::macRole(iface);
-        parent = aParent;
     }
 
     return self;
 }
 
-+ (QCocoaAccessibleElement *)createElementWithId:(QAccessible::Id)anId parent:(id)aParent
++ (id)elementWithId:(QAccessible::Id)anId
 {
-    return [[self alloc] initWithId:anId parent:aParent];
+    Q_ASSERT(anId);
+    if (!anId)
+        return nil;
+
+    QAccessibleCache *cache = QAccessibleCache::instance();
+
+    QCocoaAccessibleElement *element = cache->elementForId(anId);
+    if (!element) {
+        QAccessibleInterface *iface = QAccessible::accessibleInterface(anId);
+        Q_ASSERT(iface);
+        if (!iface)
+            return nil;
+        element = [[self alloc] initWithId:anId];
+        cache->insertElement(anId, element);
+    }
+    return element;
+}
+
+- (void)invalidate {
+    axid = 0;
+    NSAccessibilityPostNotification(self, NSAccessibilityUIElementDestroyedNotification);
+    [self release];
 }
 
 - (void)dealloc {
@@ -98,6 +120,10 @@
     return [NSNumber numberWithInt: newlines];
 }
 
+- (BOOL) accessibilityNotifiesWhenDestroyed {
+    return YES;
+}
+
 - (NSArray *)accessibilityAttributeNames {
     static NSArray *defaultAttributes = nil;
 
@@ -145,6 +171,26 @@
     return [attributes autorelease];
 }
 
+- (id)parentElement {
+    QAccessibleInterface *iface = QAccessible::accessibleInterface(axid);
+    if (!iface)
+        return nil;
+
+    if (QWindow *window = iface->window()) {
+        QCocoaWindow *win = static_cast<QCocoaWindow*>(window->handle());
+        return win->qtView();
+    }
+
+    QAccessibleInterface *parent = iface->parent();
+    if (!parent) {
+        qWarning() << "INVALID PARENT FOR INTERFACE: " << iface;
+        return nil;
+    }
+
+    QAccessible::Id parentId = QAccessible::uniqueId(parent);
+    return [QCocoaAccessibleElement elementWithId: parentId];
+}
+
 - (id)accessibilityAttributeValue:(NSString *)attribute {
     QAccessibleInterface *iface = QAccessible::accessibleInterface(axid);
     if (!iface) {
@@ -157,19 +203,19 @@
     } else if ([attribute isEqualToString:NSAccessibilityRoleDescriptionAttribute]) {
         return NSAccessibilityRoleDescription(role, nil);
     } else if ([attribute isEqualToString:NSAccessibilityChildrenAttribute]) {
-        return QCocoaAccessible::unignoredChildren(self, iface);
+        return QCocoaAccessible::unignoredChildren(iface);
     } else if ([attribute isEqualToString:NSAccessibilityFocusedAttribute]) {
         // Just check if the app thinks we're focused.
         id focusedElement = [NSApp accessibilityAttributeValue:NSAccessibilityFocusedUIElementAttribute];
         return [NSNumber numberWithBool:[focusedElement isEqual:self]];
     } else if ([attribute isEqualToString:NSAccessibilityParentAttribute]) {
-        return NSAccessibilityUnignoredAncestor(parent);
+        return NSAccessibilityUnignoredAncestor([self parentElement]);
     } else if ([attribute isEqualToString:NSAccessibilityWindowAttribute]) {
         // We're in the same window as our parent.
-        return [parent accessibilityAttributeValue:NSAccessibilityWindowAttribute];
+        return [[self parentElement] accessibilityAttributeValue:NSAccessibilityWindowAttribute];
     } else if ([attribute isEqualToString:NSAccessibilityTopLevelUIElementAttribute]) {
         // We're in the same top level element as our parent.
-        return [parent accessibilityAttributeValue:NSAccessibilityTopLevelUIElementAttribute];
+        return [[self parentElement] accessibilityAttributeValue:NSAccessibilityTopLevelUIElementAttribute];
     } else if ([attribute isEqualToString:NSAccessibilityPositionAttribute]) {
         QPoint qtPosition = iface->rect().topLeft();
         QSize qtSize = iface->rect().size();
@@ -403,20 +449,26 @@
         return NSAccessibilityUnignoredAncestor(self);
     }
 
-    QAccessibleInterface *childInterface = iface->childAt(point.x, qt_mac_flipYCoordinate(point.y));
-
+    int y = qt_mac_flipYCoordinate(point.y);
+    QAccessibleInterface *childInterface = iface->childAt(point.x, y);
     // No child found, meaning we hit this element.
-    if (!childInterface) {
-//        qDebug() << "Hit test returns: " << id << iface;
+    if (!childInterface)
         return NSAccessibilityUnignoredAncestor(self);
-    }
+
+    // find the deepest child at the point
+    QAccessibleInterface *childOfChildInterface = 0;
+    do {
+        childOfChildInterface = childInterface->childAt(point.x, y);
+        if (childOfChildInterface)
+            childInterface = childOfChildInterface;
+    } while (childOfChildInterface);
 
     QAccessible::Id childId = QAccessible::uniqueId(childInterface);
     // hit a child, forward to child accessible interface.
-    QCocoaAccessibleElement *accessibleElement = [QCocoaAccessibleElement createElementWithId:childId parent:self];
-    [accessibleElement autorelease];
-
-    return [accessibleElement accessibilityHitTest:point];
+    QCocoaAccessibleElement *accessibleElement = [QCocoaAccessibleElement elementWithId:childId];
+    if (accessibleElement)
+        return NSAccessibilityUnignoredAncestor(accessibleElement);
+    return NSAccessibilityUnignoredAncestor(self);
 }
 
 - (id)accessibilityFocusedUIElement {
@@ -426,17 +478,15 @@
         qWarning() << "FocusedUIElement for INVALID";
         return nil;
     }
+
     QAccessibleInterface *childInterface = iface->focusChild();
     if (childInterface) {
         QAccessible::Id childAxid = QAccessible::uniqueId(childInterface);
-        // FIXME: parent could be wrong
-        QCocoaAccessibleElement *accessibleElement = [QCocoaAccessibleElement createElementWithId:childAxid parent:self];
-        [accessibleElement autorelease];
-        return accessibleElement;
+        QCocoaAccessibleElement *accessibleElement = [QCocoaAccessibleElement elementWithId:childAxid];
+        return NSAccessibilityUnignoredAncestor(accessibleElement);
     }
 
-    // no focus found
-    return nil;
+    return NSAccessibilityUnignoredAncestor(self);
 }
 
 @end