Revert "[Cocoa] objectForEqualityCheck() is no longer necessary"

https://bugs.webkit.org/show_bug.cgi?id=263136
rdar://116934547

Reviewed by Cameron McCormack.

This reverts commit dc989b3.

267312@main [1] broke the following test:
imported/w3c/web-platform-tests/css/css-text/line-break/line-break-anywhere-overrides-uax-behavior-011.html

Before [1] we used to define a derived object from the Fonts we were trying to compare,
because we considered that CFEqual() would do a shallow comparison.

Since it is possible to generate two font objects (with different pointers) representing
the same font object, a shallow comparison wouldn’t work for us.

[1] states that CFEqual() "now” does a deep comparison, and
the derived object would have no use anymore.

However, at Source/WebCore/platform/graphics/mac/ComplexTextControllerCoreText.mm:
ComplexTextController::collectComplexTextRunsForCharacters:

We observe that the comparisons before and after [1] produce different results,
for the specific test that is failing. More specifically we can reduce it to
the render of “X͏”:

-> Without [1] the following is never true:
 if (!safeCFEqual(runFontEqualityObject.get(), font->platformData().objectForEqualityCheck().get()))

This means that the fonts are considered equal. However:

-> With [1] the following is always true:
 if (!safeCFEqual(runCTFont, font->platformData().ctFont()))

This means that the run’s font, acquired after shaping is not the same as the font passed,
so we will try to add it to the fallback font list.

* Source/WebCore/platform/graphics/FontPlatformData.h:
* Source/WebCore/platform/graphics/coretext/FontPlatformDataCoreText.cpp:
(WebCore::FontPlatformData::objectForEqualityCheck):
(WebCore::FontPlatformData::objectForEqualityCheck const):
* Source/WebCore/platform/graphics/mac/ComplexTextControllerCoreText.mm:
(WebCore::ComplexTextController::collectComplexTextRunsForCharacters):

Canonical link: https://commits.webkit.org/273377@main

Source/WebCore/platform/graphics/FontPlatformData.h

@@ -173,6 +173,8 @@ class FontPlatformData {
 
 #if USE(CORE_TEXT)
     WEBCORE_EXPORT CTFontRef registeredFont() const; // Returns nullptr iff the font is not registered, such as web fonts (otherwise returns font()).
+    static RetainPtr<CFTypeRef> objectForEqualityCheck(CTFontRef);
+    RetainPtr<CFTypeRef> objectForEqualityCheck() const;
     bool hasCustomTracking() const { return isSystemFont(); }
 
     CTFontRef font() const { return m_font.get(); }

Source/WebCore/platform/graphics/coretext/FontPlatformDataCoreText.cpp

@@ -185,6 +185,21 @@ CTFontRef FontPlatformData::ctFont() const
     return m_ctFont.get();
 }
 
+RetainPtr<CFTypeRef> FontPlatformData::objectForEqualityCheck(CTFontRef ctFont)
+{
+    auto fontDescriptor = adoptCF(CTFontCopyFontDescriptor(ctFont));
+    // FIXME: https://bugs.webkit.org/show_bug.cgi?id=138683 This is a shallow pointer compare for web fonts
+    // because the URL contains the address of the font. This means we might erroneously get false negatives.
+    auto object = adoptCF(CTFontDescriptorCopyAttribute(fontDescriptor.get(), kCTFontReferenceURLAttribute));
+    ASSERT(!object || CFGetTypeID(object.get()) == CFURLGetTypeID());
+    return object;
+}
+
+RetainPtr<CFTypeRef> FontPlatformData::objectForEqualityCheck() const
+{
+    return objectForEqualityCheck(ctFont());
+}
+
 RefPtr<SharedBuffer> FontPlatformData::openTypeTable(uint32_t table) const
 {
     if (RetainPtr<CFDataRef> data = adoptCF(CTFontCopyTable(ctFont(), table, kCTFontTableOptionNoOptions)))

Source/WebCore/platform/graphics/mac/ComplexTextControllerCoreText.mm

@@ -229,15 +229,16 @@ static CFDictionaryRef typesetterOptions()
         // Therefore, we only need to inspect which font was actually used if isSystemFallback is true.
         if (isSystemFallback) {
             CFDictionaryRef runAttributes = CTRunGetAttributes(ctRun);
-            auto runCTFont = static_cast<CTFontRef>(CFDictionaryGetValue(runAttributes, kCTFontAttributeName));
+            CTFontRef runCTFont = static_cast<CTFontRef>(CFDictionaryGetValue(runAttributes, kCTFontAttributeName));
             ASSERT(runCTFont && CFGetTypeID(runCTFont) == CTFontGetTypeID());
-            if (!safeCFEqual(runCTFont, font->platformData().ctFont())) {
+            RetainPtr<CFTypeRef> runFontEqualityObject = FontPlatformData::objectForEqualityCheck(runCTFont);
+            if (!safeCFEqual(runFontEqualityObject.get(), font->platformData().objectForEqualityCheck().get())) {
                 // Begin trying to see if runFont matches any of the fonts in the fallback list.
                 for (unsigned i = 0; !m_font.fallbackRangesAt(i).isNull(); ++i) {
                     runFont = m_font.fallbackRangesAt(i).fontForCharacter(baseCharacter);
                     if (!runFont)
                         continue;
-                    if (safeCFEqual(runFont->platformData().ctFont(), runCTFont))
+                    if (safeCFEqual(runFont->platformData().objectForEqualityCheck().get(), runFontEqualityObject.get()))
                         break;
                     runFont = nullptr;
                 }