Chromium for Mac cannot print surrogate pair in vertical writing mode

Source/platform/fonts/mac/GlyphPageTreeNodeMac.cpp

Index: Source/platform/fonts/mac/GlyphPageTreeNodeMac.cpp
diff --git a/Source/platform/fonts/mac/GlyphPageTreeNodeMac.cpp b/Source/platform/fonts/mac/GlyphPageTreeNodeMac.cpp
index 704d10df7993fdb23ba8d6cf8bd8793ac8ef99ad..cb1e6a5bfdece7114ed55d41df57d5a817707d9f 100644
--- a/Source/platform/fonts/mac/GlyphPageTreeNodeMac.cpp
+++ b/Source/platform/fonts/mac/GlyphPageTreeNodeMac.cpp
@@ -45,6 +45,16 @@ static bool shouldUseCoreText(UChar* buffer, unsigned bufferLength, const Simple
 {
     if (fontData->platformData().isCompositeFontReference())
         return true;
+
+    // CoreText doesn't have vertical glyphs of surrogate pair characters, and we draw broken glyphs.

[leviw_travelin_and_unemployed, 2014/01/28 19:16:40]

If I understand this patch, your change is to make us no longer draw broken
glyphs, so this comment seems wrong.

+    // To work around that, we should not use CoreText, but this always returns horizontal glyphs.
+    // FIXME: We should use vertical glyphs.

[leviw_travelin_and_unemployed, 2014/01/28 19:16:40]

Please add a reference to a bug number.

+    if (bufferLength >= 2 && U_IS_SURROGATE(buffer[0]) && fontData->hasVerticalGlyphs()) {
+        ASSERT(U_IS_SURROGATE_LEAD(buffer[0]));
+        ASSERT(U_IS_TRAIL(buffer[1]));
+        return false;
+    }
+
     if (fontData->platformData().widthVariant() != RegularWidth || fontData->hasVerticalGlyphs()) {
         // Ideographs don't have a vertical variant or width variants.
         for (unsigned i = 0; i < bufferLength; ++i) {