Symbian^3 workaround: Avoid usage of linked fonts.

"Linked Fonts" are a new feature in Symbian^3, first used in SR11.1.
This patch prevents Qt from using linked fonts in any way.

Avkon based applications benefit from Linked Fonts because they can now
transparently render multi-script text, e.g. Latin/Chinese/Japanese (Qt
does that by its own and calls the feature 'font merging'). From Qt's
poing of view, Linked Fonts are a severe regression in Symbian's API.
1 Font table Api for linked fonts is extremely slow
2 'cmap' tables do not seem to reflect the "linkage", causing garbled
  text or crashes.
3 Linked fonts appear with cryptic type face names, and are redundant
  since they are just compounds of the other, real fonts.

This patch adds a detection of Linked Fonts using
CLinkedTypefaceSpecification and prevents their inclusion into
QFontDataBase. Furthermore, it detects if the Symbian System font is a
Linked font and if needed tries to fall back to a classical Symbian
system font, e.g. "Nokia Sans S60" or "Series 60 Sans". Fallback to
"Pure" will need to be added, later on.

Task-Number: QTBUG-20007
Co-authored-by: Miklos Vlasa
Reviewed-by: mread <qt-info@nokia.com>

2 files changed, 62 insertions, 9 deletions

diff --git a/src/gui/text/qfont_s60.cpp b/src/gui/text/qfont_s60.cpp
index a7a2547..2218617 100644
--- a/src/gui/text/qfont_s60.cpp
+++ b/src/gui/text/qfont_s60.cpp
@@ -55,6 +55,24 @@ Q_GLOBAL_STATIC_WITH_INITIALIZER(QStringList, fontFamiliesOnFontServer, {
     // Therefore, we are allowed to cache the list.
     x->append(qt_symbian_fontFamiliesOnFontServer());
 });
+
+extern bool qt_symbian_isLinkedFont(const TDesC &typefaceName); // qfontdatabase_s60.cpp
+
+static QString classicalSymbianSystemFont()
+{
+    static QString font;
+    if (font.isEmpty()) {
+        static const char* const classicSymbianSystemFonts[] = { "Nokia Sans S60", "Series 60 Sans" };
+        for (int i = 0; i < sizeof classicSymbianSystemFonts / sizeof classicSymbianSystemFonts[0]; ++i) {
+            const QString classicFont = QLatin1String(classicSymbianSystemFonts[i]);
+            if (fontFamiliesOnFontServer()->contains(classicFont)) {
+                font = classicFont;
+                break;
+            }
+        }
+    }
+    return font;
+}
 #endif // QT_NO_FREETYPE
 
 QString QFont::lastResortFont() const
@@ -84,6 +102,10 @@ QString QFont::lastResortFamily() const
         S60->screenDevice()->ReleaseFont(font);
         
         lock.relock();
+
+        // We must not return a Symbian Linked Font. See QTBUG-20007
+        if (qt_symbian_isLinkedFont(spec.iTypeface.iName) && !classicalSymbianSystemFont().isEmpty())
+            family = classicalSymbianSystemFont();
     }
     return family;
 #else // QT_NO_FREETYPE
@@ -103,14 +125,9 @@ QString QFont::defaultFamily() const
 {
 #ifdef QT_NO_FREETYPE
     switch(d->request.styleHint) {
-        case QFont::SansSerif: {
-            static const char* const preferredSansSerif[] = {"Nokia Sans S60", "Series 60 Sans"};
-            for (int i = 0; i < sizeof preferredSansSerif / sizeof preferredSansSerif[0]; ++i) {
-                const QString sansSerif = QLatin1String(preferredSansSerif[i]);
-                if (fontFamiliesOnFontServer()->contains(sansSerif))
-                    return sansSerif;
-            }
-        }
+        case QFont::SansSerif:
+        if (!classicalSymbianSystemFont().isEmpty())
+            return classicalSymbianSystemFont();
         // No break. Intentional fall through.
         default:
             return lastResortFamily();
diff --git a/src/gui/text/qfontdatabase_s60.cpp b/src/gui/text/qfontdatabase_s60.cpp
index 1eb4242..ffecca7 100644
--- a/src/gui/text/qfontdatabase_s60.cpp
+++ b/src/gui/text/qfontdatabase_s60.cpp
@@ -58,8 +58,41 @@
 #endif // SYMBIAN_ENABLE_SPLIT_HEADERS
 #endif // QT_NO_FREETYPE
 
+#ifndef SYMBIAN_VERSION_9_4
+#define SYMBIAN_LINKEDFONTS_SUPPORTED
+#endif // !SYMBIAN_VERSION_9_4
+
+#ifdef SYMBIAN_LINKEDFONTS_SUPPORTED
+#include <linkedfonts.h>
+#endif // SYMBIAN_LINKEDFONTS_SUPPORTED
+
 QT_BEGIN_NAMESPACE
 
+#ifdef SYMBIAN_LINKEDFONTS_SUPPORTED
+static bool isLinkedFontL(const TDesC &aTypefaceName)
+{
+    CLinkedTypefaceSpecification *linkedspec = CLinkedTypefaceSpecification::NewLC(aTypefaceName);
+    CFbsTypefaceStore *tfs = CFbsTypefaceStore::NewL(NULL);
+    CleanupStack::PushL(tfs);
+    linkedspec->FetchLinkedTypefaceSpecificationL(*tfs);
+    CleanupStack::PopAndDestroy(tfs);
+    CleanupStack::PopAndDestroy(linkedspec);
+    return true;
+}
+#endif // SYMBIAN_LINKEDFONTS_SUPPORTED
+
+bool qt_symbian_isLinkedFont(const TDesC &typefaceName) // Also used in qfont_s60.cpp
+{
+    bool isLinkedFont = false;
+#ifdef SYMBIAN_LINKEDFONTS_SUPPORTED
+    if (RFbsSession::Connect() == KErrNone) {
+        TRAP_IGNORE(isLinkedFont = isLinkedFontL(typefaceName));
+        RFbsSession::Disconnect();
+    }
+#endif // SYMBIAN_LINKEDFONTS_SUPPORTED
+    return isLinkedFont;
+}
+
 QStringList qt_symbian_fontFamiliesOnFontServer() // Also used in qfont_s60.cpp
 {
     QStringList result;
@@ -468,7 +501,10 @@ static bool registerScreenDeviceFont(int screenDeviceFontIndex,
                                      const QSymbianFontDatabaseExtrasImplementation *dbExtras)
 {
     TTypefaceSupport typefaceSupport;
-        S60->screenDevice()->TypefaceSupport(typefaceSupport, screenDeviceFontIndex);
+    S60->screenDevice()->TypefaceSupport(typefaceSupport, screenDeviceFontIndex);
+
+    if (qt_symbian_isLinkedFont(typefaceSupport.iTypeface.iName))
+        return false;
 
     QString familyName((const QChar*)typefaceSupport.iTypeface.iName.Ptr(), typefaceSupport.iTypeface.iName.Length());
     if (qt_symbian_fontNameHasAppFontMarker(familyName)) {