AX: Move attributedStringForNSRange off the main thread when possible.

https://bugs.webkit.org/show_bug.cgi?id=255789
<rdar://problem/108369924>

Reviewed by Chris Fleizach.

This patch avoids hitting the main thread for requests of the AttributedString for NSRanges contained in a text control. That is the most common case during text editing. To accomplish this, textMarkerRangeForNSRange needs to build a TextMarkerRange based on CharacterOffsets and not in VisiblePositions. In addition, the ranges used in caching the TextContent and the AttributedString also need to be based on CharacterOffsets.

* Source/WebCore/accessibility/AXTextMarker.h:
(WebCore::AXTextMarkerRange::operator bool const): Clean up.
* Source/WebCore/accessibility/AccessibilityObject.cpp:
(WebCore::AccessibilityObject::textContent const):
* Source/WebCore/accessibility/cocoa/AccessibilityObjectCocoa.mm:
(WebCore::AccessibilityObject::textMarkerRangeForNSRange const):
* Source/WebCore/accessibility/isolatedtree/mac/AXIsolatedObjectMac.mm:
(WebCore::AXIsolatedObject::initializePlatformProperties):
(WebCore::AXIsolatedObject::textMarkerRangeForNSRange const):
(WebCore::AXIsolatedObject::attributedStringForTextMarkerRange const):
(WebCore::AXIsolatedObject::cachedAttributedStringForTextMarkerRange const): Deleted.
* Source/WebCore/accessibility/isolatedtree/AXIsolatedObject.h:
* Source/WebCore/accessibility/mac/WebAccessibilityObjectWrapperMac.mm:
(-[WebAccessibilityObjectWrapper attributedStringForNSRange:]):
(-[WebAccessibilityObjectWrapper rtfForNSRange:]):
(-[WebAccessibilityObjectWrapper accessibilityAttributeValue:forParameter:]):
(-[WebAccessibilityObjectWrapper doAXAttributedStringForRange:]): Renamed.
(-[WebAccessibilityObjectWrapper doAXRTFForRange:]): Renamed.

Canonical link: https://commits.webkit.org/263270@main

Source/WebCore/accessibility/AXTextMarker.h

@@ -151,7 +151,7 @@ class AXTextMarkerRange {
     AXTextMarkerRange(AXID treeID, AXID objectID, unsigned offset, unsigned length);
     AXTextMarkerRange() = default;
 
-    operator bool() const { return !m_start.isNull() && !m_end.isNull(); }
+    operator bool() const { return m_start && m_end; }
     operator VisiblePositionRange() const;
     std::optional<SimpleRange> simpleRange() const;
 

Source/WebCore/accessibility/AccessibilityObject.cpp

@@ -2846,7 +2846,12 @@ std::optional<String> AccessibilityObject::textContent() const
     if (!hasTextContent())
         return std::nullopt;
 
-    if (auto range = simpleRange())
+    std::optional<SimpleRange> range;
+    if (isTextControl())
+        range = rangeForPlainTextRange({ 0, text().length() });
+    else
+        range = simpleRange();
+    if (range)
         return stringForRange(*range);
     return std::nullopt;
 }

Source/WebCore/accessibility/cocoa/AccessibilityObjectCocoa.mm

@@ -217,7 +217,19 @@ static bool isDescriptiveText(AccessibilityTextSource textSource)
 {
     if (range.location == NSNotFound)
         return { };
-    return { visiblePositionForIndex(range.location), visiblePositionForIndex(range.location + range.length) };
+
+    if (!isTextControl())
+        return { visiblePositionForIndex(range.location), visiblePositionForIndex(range.location + range.length) };
+
+    if (range.location + range.length > text().length())
+        return { };
+
+    if (auto* cache = axObjectCache()) {
+        auto start = cache->characterOffsetForIndex(range.location, this);
+        auto end = cache->characterOffsetForIndex(range.location + range.length, this);
+        return cache->rangeForUnorderedCharacterOffsets(start, end);
+    }
+    return { };
 }
 
 // NSAttributedString support.

Source/WebCore/accessibility/isolatedtree/AXIsolatedObject.h

@@ -473,7 +473,6 @@ class AXIsolatedObject final : public AXCoreObject {
     unsigned textLength() const override;
 #if PLATFORM(COCOA)
     RetainPtr<NSAttributedString> attributedStringForTextMarkerRange(AXTextMarkerRange&&, SpellCheck) const override;
-    NSAttributedString *cachedAttributedStringForTextMarkerRange(const AXTextMarkerRange&, SpellCheck) const;
 #endif
     AXObjectCache* axObjectCache() const override;
     Element* actionElement() const override;

Source/WebCore/accessibility/isolatedtree/mac/AXIsolatedObjectMac.mm

@@ -41,7 +41,12 @@
 
     RetainPtr<NSAttributedString> attributedText;
     if (object->hasAttributedText()) {
-        if (auto range = object->simpleRange()) {
+        std::optional<SimpleRange> range;
+        if (isTextControl())
+            range = rangeForPlainTextRange({ 0, object->text().length() });
+        else
+            range = object->simpleRange();
+        if (range) {
             if ((attributedText = object->attributedStringForRange(*range, SpellCheck::Yes)))
                 setProperty(AXPropertyName::AttributedText, attributedText);
         }
@@ -163,29 +168,25 @@
 
 RetainPtr<NSAttributedString> AXIsolatedObject::attributedStringForTextMarkerRange(AXTextMarkerRange&& markerRange, SpellCheck spellCheck) const
 {
-    if (NSAttributedString *cachedString = cachedAttributedStringForTextMarkerRange(markerRange, spellCheck))
-        return cachedString;
-
-    return Accessibility::retrieveValueFromMainThread<RetainPtr<NSAttributedString>>([markerRange = WTFMove(markerRange), &spellCheck, this] () mutable -> RetainPtr<NSAttributedString> {
-        if (RefPtr axObject = associatedAXObject())
-            return axObject->attributedStringForTextMarkerRange(WTFMove(markerRange), spellCheck);
-        return { };
-    });
-}
+    if (!markerRange)
+        return nil;
 
-NSAttributedString *AXIsolatedObject::cachedAttributedStringForTextMarkerRange(const AXTextMarkerRange& markerRange, SpellCheck spellCheck) const
-{
     // At the moment we are only handling ranges that are contained in a single object, and for which we cached the AttributeString.
     // FIXME: Extend to cases where the range expands multiple objects.
 
+    auto attributedText = propertyValue<RetainPtr<NSAttributedString>>(AXPropertyName::AttributedText);
+    if (!attributedText) {
+        return Accessibility::retrieveValueFromMainThread<RetainPtr<NSAttributedString>>([markerRange = WTFMove(markerRange), &spellCheck, this] () mutable -> RetainPtr<NSAttributedString> {
+            if (RefPtr axObject = associatedAXObject())
+                return axObject->attributedStringForTextMarkerRange(WTFMove(markerRange), spellCheck);
+            return { };
+        });
+    }
+
     auto nsRange = markerRange.nsRange();
     if (!nsRange)
         return nil;
 
-    auto attributedText = propertyValue<RetainPtr<NSAttributedString>>(AXPropertyName::AttributedText);
-    if (!attributedText)
-        return nil;
-
     if (!attributedStringContainsRange(attributedText.get(), *nsRange))
         return nil;
 

Source/WebCore/accessibility/mac/WebAccessibilityObjectWrapperMac.mm

@@ -2804,16 +2804,12 @@ - (NSString*)accessibilityActionDescription:(NSString*)action
 
 // The CFAttributedStringType representation of the text associated with this accessibility
 // object that is specified by the given range.
-- (NSAttributedString *)doAXAttributedStringForRange:(NSRange)range
+- (NSAttributedString *)attributedStringForNSRange:(const NSRange&)range
 {
-    return Accessibility::retrieveAutoreleasedValueFromMainThread<NSAttributedString *>([&range, protectedSelf = retainPtr(self)] () -> RetainPtr<NSAttributedString> {
-        auto* backingObject = protectedSelf.get().axBackingObject;
-        if (!backingObject)
-            return nil;
-
-        auto webRange = backingObject->rangeForPlainTextRange(range);
-        return [protectedSelf attributedStringForTextMarkerRange:textMarkerRangeFromRange(backingObject->axObjectCache(), webRange) spellCheck:AXCoreObject::SpellCheck::Yes];
-    });
+    auto* backingObject = self.axBackingObject;
+    if (!backingObject)
+        return nil;
+    return backingObject->attributedStringForTextMarkerRange(backingObject->textMarkerRangeForNSRange(range), AXCoreObject::SpellCheck::Yes).autorelease();
 }
 
 - (NSInteger)_indexForTextMarker:(AXTextMarkerRef)markerRef
@@ -2857,9 +2853,9 @@ - (AXTextMarkerRef)_textMarkerForIndex:(NSInteger)textIndex
 
 // The RTF representation of the text associated with this accessibility object that is
 // specified by the given range.
-- (NSData *)doAXRTFForRange:(NSRange)range
+- (NSData *)rtfForNSRange:(const NSRange&)range
 {
-    NSAttributedString *attrString = [self doAXAttributedStringForRange:range];
+    NSAttributedString *attrString = [self attributedStringForNSRange:range];
     return [attrString RTFFromRange:NSMakeRange(0, attrString.length) documentAttributes:@{ }];
 }
 
@@ -3395,6 +3391,7 @@ - (id)accessibilityAttributeValue:(NSString*)attribute forParameter:(id)paramete
             auto* cache = backingObject->axObjectCache();
             if (!cache)
                 return String();
+
             auto start = cache->characterOffsetForIndex(range.location, backingObject);
             auto end = cache->characterOffsetForIndex(range.location + range.length, backingObject);
             auto range = cache->rangeForUnorderedCharacterOffsets(start, end);
@@ -3630,11 +3627,11 @@ - (id)accessibilityAttributeValue:(NSString*)attribute forParameter:(id)paramete
             return [NSValue valueWithRect:rect];
         }
 
-        if ([attribute isEqualToString: (NSString*)kAXRTFForRangeParameterizedAttribute])
-            return rangeSet ? [self doAXRTFForRange:range] : nil;
+        if ([attribute isEqualToString:(NSString *)kAXRTFForRangeParameterizedAttribute])
+            return rangeSet ? [self rtfForNSRange:range] : nil;
 
         if ([attribute isEqualToString:(NSString *)kAXAttributedStringForRangeParameterizedAttribute])
-            return rangeSet ? [self doAXAttributedStringForRange:range] : nil;
+            return rangeSet ? [self attributedStringForNSRange:range] : nil;
 
         if ([attribute isEqualToString: (NSString*)kAXStyleRangeForIndexParameterizedAttribute]) {
             PlainTextRange textRange = backingObject->doAXStyleRangeForIndex([number intValue]);