Get rid of requiresOpenType() helper

There is already an array of writing systems for which
GSUB|GPOS table is required
(also rename it from "openType" to "capabilityForWritingSystem",
to reflect its meaning).

Change-Id: I7cfd4a80d5ca13f9312b3644b2bd738d6015c71c
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp

@@ -62,12 +62,6 @@ static inline int mapToQtWeightForRange(int fcweight, int fcLower, int fcUpper,
     return qtLower + ((fcweight - fcLower) * (qtUpper - qtLower)) / (fcUpper - fcLower);
 }
 
-static inline bool requiresOpenType(int writingSystem)
-{
-    return ((writingSystem >= QFontDatabase::Syriac && writingSystem <= QFontDatabase::Sinhala)
-            || writingSystem == QFontDatabase::Khmer || writingSystem == QFontDatabase::Nko);
-}
-
 static inline int weightFromFcWeight(int fcweight)
 {
     // Font Config uses weights from 0 to 215 (the highest enum value) while QFont ranges from
@@ -293,10 +287,10 @@ static const char *languageForWritingSystem[] = {
 Q_STATIC_ASSERT(sizeof(languageForWritingSystem) / sizeof(const char *) == QFontDatabase::WritingSystemsCount);
 
 #if FC_VERSION >= 20297
-// Newer FontConfig let's us sort out fonts that contain certain glyphs, but no
-// open type tables for is directly. Do this so we don't pick some strange
-// pseudo unicode font
-static const char *openType[] = {
+// Newer FontConfig let's us sort out fonts that report certain scripts support,
+// but no open type tables for handling them correctly.
+// Check the reported script presence in the FC_CAPABILITY's "otlayout:" section.
+static const char *capabilityForWritingSystem[] = {
     0,     // Any
     0,  // Latin
     0,  // Greek
@@ -332,7 +326,7 @@ static const char *openType[] = {
     0, // Runic
     "nko " // N'Ko
 };
-Q_STATIC_ASSERT(sizeof(openType) / sizeof(const char *) == QFontDatabase::WritingSystemsCount);
+Q_STATIC_ASSERT(sizeof(capabilityForWritingSystem) / sizeof(*capabilityForWritingSystem) == QFontDatabase::WritingSystemsCount);
 #endif
 
 static const char *getFcFamilyForStyleHint(const QFont::StyleHint style)
@@ -438,11 +432,10 @@ static void populateFromPattern(FcPattern *pattern)
 #if FC_VERSION >= 20297
     FcChar8 *cap = Q_NULLPTR;
     for (int j = 1; j < QFontDatabase::WritingSystemsCount; ++j) {
-        if (writingSystems.supported(QFontDatabase::WritingSystem(j))
-            && requiresOpenType(j) && openType[j]) {
+        if (capabilityForWritingSystem[j] && writingSystems.supported(QFontDatabase::WritingSystem(j))) {
             if (cap == Q_NULLPTR)
                 res = FcPatternGetString(pattern, FC_CAPABILITY, 0, &cap);
-            if (res == FcResultMatch && strstr(reinterpret_cast<const char *>(cap), openType[j]) == 0)
+            if (res == FcResultMatch && strstr(reinterpret_cast<const char *>(cap), capabilityForWritingSystem[j]) == 0)
                 writingSystems.setSupported(QFontDatabase::WritingSystem(j),false);
         }
     }