Fix surrogate pair handling in QCoreTextFontEngine

The number of glyphs returned should take surrogate pairs into account.
The glyphs array and advances array as well. This follows the approach
in QFontEngineFT in general.

Change-Id: Ic53faa5e38c2219b987d76aec434558dad92015a
Reviewed-by: Zeno Albisser <zeno.albisser@nokia.com>

1 files changed, 31 insertions, 5 deletions

diff --git a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
index 746cba6762..846b657bb4 100644
--- a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
+++ b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
@@ -190,20 +190,46 @@ void QCoreTextFontEngine::init()
 bool QCoreTextFontEngine::stringToCMap(const QChar *str, int len, QGlyphLayout *glyphs,
                                        int *nglyphs, QTextEngine::ShaperFlags flags) const
 {
-    *nglyphs = len;
     QCFType<CFStringRef> cfstring;
 
     QVarLengthArray<CGGlyph> cgGlyphs(len);
     CTFontGetGlyphsForCharacters(ctfont, (const UniChar*)str, cgGlyphs.data(), len);
 
-    for (int i = 0; i < len; ++i)
-        if (cgGlyphs[i])
-            glyphs->glyphs[i] = cgGlyphs[i];
+    int glyph_pos = 0;
+    for (int i = 0; i < len; ++i) {
+        if (cgGlyphs[i]) {
+            glyphs->glyphs[glyph_pos] = cgGlyphs[i];
+            if (glyph_pos < i)
+                cgGlyphs[glyph_pos] = cgGlyphs[i];
+        }
+        glyph_pos++;
+
+        // If it's a non-BMP char, skip the lower part of surrogate pair and go
+        // directly to the next char without increasing glyph_pos
+        if (str[i].isHighSurrogate() && i < len-1 && str[i+1].isLowSurrogate())
+            ++i;
+    }
 
+    *nglyphs = glyph_pos;
     if (flags & QTextEngine::GlyphIndicesOnly)
         return true;
 
-    loadAdvancesForGlyphs(ctfont, cgGlyphs, glyphs, len, flags, fontDef);
+    QVarLengthArray<CGSize> advances(glyph_pos);
+    CTFontGetAdvancesForGlyphs(ctfont, kCTFontHorizontalOrientation, cgGlyphs.data(), advances.data(), glyph_pos);
+
+    for (int i = 0; i < glyph_pos; ++i) {
+        if (glyphs->glyphs[i] & 0xff000000)
+            continue;
+        glyphs->advances_x[i] = QFixed::fromReal(advances[i].width);
+        glyphs->advances_y[i] = QFixed::fromReal(advances[i].height);
+    }
+
+    if (fontDef.styleStrategy & QFont::ForceIntegerMetrics) {
+        for (int i = 0; i < glyph_pos; ++i) {
+            glyphs->advances_x[i] = glyphs->advances_x[i].round();
+            glyphs->advances_y[i] = glyphs->advances_y[i].round();
+        }
+    }
     return true;
 }