[Webkit-unassigned] [Bug 229556] AX: Make PDFs loaded via <embed> accessible

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=229556

--- Comment #15 from Andres Gonzalez <andresg_22 at apple.com> ---
(In reply to Tyler Wilcock from comment #13)
> Created attachment 437808 [details]
> Patch

--- a/Source/WebCore/accessibility/mac/WebAccessibilityObjectWrapperMac.mm
+++ a/Source/WebCore/accessibility/mac/WebAccessibilityObjectWrapperMac.mm

@@ -2944,6 +2948,25 @@ ALLOW_DEPRECATED_IMPLEMENTATIONS_END
     if (axObject) {
         if (axObject->isAttachment() && [axObject->wrapper() attachmentView])
             return [axObject->wrapper() attachmentView];
+        auto* widget = axObject->widget();
+        if (is<PluginViewBase>(widget)) {
+            id hitTestResult = widget->accessibilityHitTest(IntPoint(point));
+            BOOL accessibilityIsIgnored = YES;
+            BOOL isAccessibilityElement = NO;
+
+            ALLOW_DEPRECATED_DECLARATIONS_BEGIN
+            if ([hitTestResult respondsToSelector:@selector(accessibilityIsIgnored)])
+                accessibilityIsIgnored = [hitTestResult accessibilityIsIgnored];
+            ALLOW_DEPRECATED_DECLARATIONS_END
+
+            if ([hitTestResult respondsToSelector:@selector(isAccessibilityElement)])
+                isAccessibilityElement = [hitTestResult isAccessibilityElement];
+
+            // Check if either selector exposes the element, because some classes
+            // have conflicting implementations (such as PDFLayerController which returns YES in both cases).
+            if (!accessibilityIsIgnored || isAccessibilityElement)
+                return hitTestResult;
+        }
         return NSAccessibilityUnignoredAncestor(axObject->wrapper());
     }
     return NSAccessibilityUnignoredAncestor(self);

I would suggest getting rid of the bools and changing this logic to:

if (![hitTestResult respondsToSelector:@selector(isAccessibilityElement)]
    || ![hitTestResult isAccessibilityElement])
    return NSAccessibilityUnignoredAncestor(axObject->wrapper());
// isAccessibilityElement is a required selector for all platform accessible objects.

ALLOW_DEPRECATED_DECLARATIONS_BEGIN
if ([hitTestResult respondsToSelector:@selector(accessibilityIsIgnored)])
    && [hitTestResult accessibilityIsIgnored];
    return NSAccessibilityUnignoredAncestor(axObject->wrapper());
ALLOW_DEPRECATED_DECLARATIONS_END
// accessibilityIsIgnored is optional, implemented by web objects, but not necessarily by plugins.

return hitTestResult;

@@ -3694,6 +3717,16 @@ enum class TextUnit {
     });
 }

+static BOOL isPluginMatchingCriteria(AXCoreObject* axObject, const AccessibilitySearchCriteria& criteria)

What is the purpose of this function? Searches can start at any object, plug-in or not, and the results should include all matching objects plug-in or not.

@@ -3797,6 +3830,10 @@ ALLOW_DEPRECATED_IMPLEMENTATIONS_END

     if ([attribute isEqualToString:NSAccessibilityUIElementCountForSearchPredicateParameterizedAttribute]) {
         AccessibilitySearchCriteria criteria = accessibilitySearchCriteriaForSearchPredicateParameterizedAttribute(dictionary);
+        if (isPluginMatchingCriteria(backingObject, criteria)) {
+            auto* widgetChildren = [self renderWidgetChildren];
+            return @(std::min([widgetChildren count], NSUInteger(criteria.resultsLimit)));
+        }

There is no matching performed here, we don't want to return all the children of the starting object.

@@ -3804,6 +3841,13 @@ ALLOW_DEPRECATED_IMPLEMENTATIONS_END

     if ([attribute isEqualToString:NSAccessibilityUIElementsForSearchPredicateParameterizedAttribute]) {
         AccessibilitySearchCriteria criteria = accessibilitySearchCriteriaForSearchPredicateParameterizedAttribute(dictionary);
+        // If our object is a plugin, it won't have non-widget children to search through.
+        // If the criteria allows, search through `renderWidgetChildren` instead.
+        if (isPluginMatchingCriteria(backingObject, criteria)) {
+            auto* widgetChildren = [self renderWidgetChildren];
+            NSUInteger matchingChildrenCount = std::min([widgetChildren count], NSUInteger(criteria.resultsLimit));
+            return [widgetChildren subarrayWithRange:NSMakeRange(0, matchingChildrenCount)];
+        }

Same here, there is no matching done, we don't want to return just the children of the start object.

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