Use maximum ascent/descent/leading from fallback fonts in shaping

When shaping a QScriptItem with a multi font engine, currently we
only take the ascent/descent/leading from the primary (first) font
engine in that multi font engine, however, subsequent engines used
during shaping may have larger ascent/descent/leading, disregarding
them may cause clipping issues in some cases.

It's fixed by checking each font engine used in the shaping process
and take the maximum value instead of the first one. On ATSUI we
merely make it compile.

Task-number: QTBUG-16719
Reviewed-by: Eskil
(cherry picked from commit c501403cb5a0c9ec21b00e0c2f640ae85566e0cf)

6 files changed, 20 insertions, 8 deletions

diff --git a/src/gui/text/qfontengine_coretext.mm b/src/gui/text/qfontengine_coretext.mm
index c4d2d47f59..d4df2183ed 100644
--- a/src/gui/text/qfontengine_coretext.mm
+++ b/src/gui/text/qfontengine_coretext.mm
@@ -162,8 +162,10 @@ uint QCoreTextFontEngineMulti::fontIndexForFont(CTFontRef font) const
     return engines.count() - 1;
 }
 
-bool QCoreTextFontEngineMulti::stringToCMap(const QChar *str, int len, QGlyphLayout *glyphs, int *nglyphs, QTextEngine::ShaperFlags flags,
-                  unsigned short *logClusters, const HB_CharAttributes *) const
+bool QCoreTextFontEngineMulti::stringToCMap(const QChar *str, int len, QGlyphLayout *glyphs,
+                                            int *nglyphs, QTextEngine::ShaperFlags flags,
+                                            unsigned short *logClusters, const HB_CharAttributes *,
+                                            QScriptItem *si) const
 {
     QCFType<CFStringRef> cfstring = CFStringCreateWithCharactersNoCopy(0,
                                                                reinterpret_cast<const UniChar *>(str),
@@ -254,7 +256,12 @@ bool QCoreTextFontEngineMulti::stringToCMap(const QChar *str, int len, QGlyphLay
             if (!runAttribs)
                 runAttribs = attributeDict;
             CTFontRef runFont = static_cast<CTFontRef>(CFDictionaryGetValue(runAttribs, NSFontAttributeName));
-            const uint fontIndex = (fontIndexForFont(runFont) << 24);
+            uint fontIndex = fontIndexForFont(runFont);
+            const QFontEngine *engine = engineAt(fontIndex);
+            fontIndex <<= 24;
+            si->ascent = qMax(engine->ascent(), si->ascent);
+            si->descent = qMax(engine->descent(), si->descent);
+            si->leading = qMax(engine->leading(), si->leading);
             //NSLog(@"Run Font Name = %@", CTFontCopyFamilyName(runFont));
             if (endWithPDF)
                 glyphCount--;
diff --git a/src/gui/text/qfontengine_coretext_p.h b/src/gui/text/qfontengine_coretext_p.h
index aa5f91a20c..bb80a9b2f3 100644
--- a/src/gui/text/qfontengine_coretext_p.h
+++ b/src/gui/text/qfontengine_coretext_p.h
@@ -120,7 +120,8 @@ public:
                               QTextEngine::ShaperFlags flags) const;
     bool stringToCMap(const QChar *str, int len, QGlyphLayout *glyphs, int *nglyphs,
                       QTextEngine::ShaperFlags flags,
-                      unsigned short *logClusters, const HB_CharAttributes *charAttributes) const;
+                      unsigned short *logClusters, const HB_CharAttributes *charAttributes,
+                      QScriptItem *si) const;
 
     virtual const char *name() const { return "CoreText"; }
 protected:
diff --git a/src/gui/text/qfontengine_mac.mm b/src/gui/text/qfontengine_mac.mm
index 673a7c86fa..9f094ad7d1 100644
--- a/src/gui/text/qfontengine_mac.mm
+++ b/src/gui/text/qfontengine_mac.mm
@@ -377,7 +377,7 @@ bool QFontEngineMacMulti::stringToCMap(const QChar *str, int len, QGlyphLayout *
 }
 
 bool QFontEngineMacMulti::stringToCMap(const QChar *str, int len, QGlyphLayout *glyphs, int *nglyphs, QTextEngine::ShaperFlags flags,
-                                       unsigned short *logClusters, const HB_CharAttributes *charAttributes) const
+                                       unsigned short *logClusters, const HB_CharAttributes *charAttributes, QScriptItem *) const
 {
     if (*nglyphs < len) {
         *nglyphs = len;
diff --git a/src/gui/text/qfontengine_mac_p.h b/src/gui/text/qfontengine_mac_p.h
index 385fa83fe9..292ea98d9a 100644
--- a/src/gui/text/qfontengine_mac_p.h
+++ b/src/gui/text/qfontengine_mac_p.h
@@ -131,7 +131,7 @@ public:
 
     virtual bool stringToCMap(const QChar *str, int len, QGlyphLayout *glyphs, int *nglyphs, QTextEngine::ShaperFlags flags) const;
     bool stringToCMap(const QChar *str, int len, QGlyphLayout *glyphs, int *nglyphs, QTextEngine::ShaperFlags flags,
-                      unsigned short *logClusters, const HB_CharAttributes *charAttributes) const;
+                      unsigned short *logClusters, const HB_CharAttributes *charAttributes, QScriptItem *) const;
 
     virtual void recalcAdvances(QGlyphLayout *, QTextEngine::ShaperFlags) const;
     virtual void doKerning(QGlyphLayout *, QTextEngine::ShaperFlags) const;
diff --git a/src/gui/text/qtextengine.cpp b/src/gui/text/qtextengine.cpp
index cc150c5965..ff27bc673f 100644
--- a/src/gui/text/qtextengine.cpp
+++ b/src/gui/text/qtextengine.cpp
@@ -1274,6 +1274,10 @@ void QTextEngine::shapeTextWithHarfbuzz(int item) const
             actualFontEngine = static_cast<QFontEngineMulti *>(font)->engine(engineIdx);
         }
 
+        si.ascent = qMax(actualFontEngine->ascent(), si.ascent);
+        si.descent = qMax(actualFontEngine->descent(), si.descent);
+        si.leading = qMax(actualFontEngine->leading(), si.leading);
+
         shaper_item.font = actualFontEngine->harfbuzzFont();
         shaper_item.face = actualFontEngine->harfbuzzFace();
 
diff --git a/src/gui/text/qtextengine_mac.cpp b/src/gui/text/qtextengine_mac.cpp
index 97e8c5b0f8..2c6e579b45 100644
--- a/src/gui/text/qtextengine_mac.cpp
+++ b/src/gui/text/qtextengine_mac.cpp
@@ -605,11 +605,11 @@ void QTextEngine::shapeTextMac(int item) const
     unsigned short *log_clusters = logClusters(&si);
 
     bool stringToCMapFailed = false;
-    if (!fe->stringToCMap(str, len, &g, &num_glyphs, flags, log_clusters, attributes())) {
+    if (!fe->stringToCMap(str, len, &g, &num_glyphs, flags, log_clusters, attributes(), &si)) {
         ensureSpace(num_glyphs);
         g = availableGlyphs(&si);
         stringToCMapFailed = !fe->stringToCMap(str, len, &g, &num_glyphs, flags, log_clusters,
-                                               attributes());
+                                               attributes(), &si);
     }
 
     if (!stringToCMapFailed) {