1 files changed, 88 insertions, 0 deletions
diff --git a/Source/WebCore/style/StyleChange.cpp b/Source/WebCore/style/StyleChange.cpp
new file mode 100644
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+++ b/Source/WebCore/style/StyleChange.cpp
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+/*
+ * Copyright (C) 2013, 2016 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "StyleChange.h"
+
+#include "RenderStyle.h"
+
+namespace WebCore {
+namespace Style {
+
+Change determineChange(const RenderStyle& s1, const RenderStyle& s2)
+{
+    if (s1.display() != s2.display())
+        return Detach;
+    if (s1.hasPseudoStyle(FIRST_LETTER) != s2.hasPseudoStyle(FIRST_LETTER))
+        return Detach;
+    // We just detach if a renderer acquires or loses a column-span, since spanning elements
+    // typically won't contain much content.
+    if (s1.columnSpan() != s2.columnSpan())
+        return Detach;
+    if (!s1.contentDataEquivalent(&s2))
+        return Detach;
+    // When text-combine property has been changed, we need to prepare a separate renderer object.
+    // When text-combine is on, we use RenderCombineText, otherwise RenderText.
+    // https://bugs.webkit.org/show_bug.cgi?id=55069
+    if (s1.hasTextCombine() != s2.hasTextCombine())
+        return Detach;
+    // We need to reattach the node, so that it is moved to the correct RenderFlowThread.
+    if (s1.flowThread() != s2.flowThread())
+        return Detach;
+    // When the region thread has changed, we need to prepare a separate render region object.
+    if (s1.regionThread() != s2.regionThread())
+        return Detach;
+    // FIXME: Multicolumn regions not yet supported (http://dev.w3.org/csswg/css-regions/#multi-column-regions)
+    // When the node has region style and changed its multicol style, we have to prepare
+    // a separate render region object.
+    if (s1.hasFlowFrom() && (s1.specifiesColumns() != s2.specifiesColumns()))
+        return Detach;
+
+    if (s1 != s2) {
+        if (s1.inheritedNotEqual(&s2))
+            return Inherit;
+
+        return NoInherit;
+    }
+    // If the pseudoStyles have changed, we want any StyleChange that is not NoChange
+    // because setStyle will do the right thing with anything else.
+    if (s1.hasAnyPublicPseudoStyles()) {
+        for (PseudoId pseudoId = FIRST_PUBLIC_PSEUDOID; pseudoId < FIRST_INTERNAL_PSEUDOID; pseudoId = static_cast<PseudoId>(pseudoId + 1)) {
+            if (s1.hasPseudoStyle(pseudoId)) {
+                RenderStyle* ps2 = s2.getCachedPseudoStyle(pseudoId);
+                if (!ps2)
+                    return NoInherit;
+                RenderStyle* ps1 = s1.getCachedPseudoStyle(pseudoId);
+                if (!ps1 || *ps1 != *ps2)
+                    return NoInherit;
+            }
+        }
+    }
+
+    return NoChange;
+}
+
+}
+}