Support the named instances of Variable Fonts

In the fontconfig, the fonts will be populated with the variable font
and the named instance from the variable font. In this patch, it will
skip the variable font, and populate the named instances from the variable font.
The FcFontMatch function ignores the FC_INDEX when match the font,
changed the code to match the FC_INDEX by iterate the font list.

[ChangeLog][Fonts] Added support for the named instances from the variable fonts.

Pick-to: 6.7
Fixes: QTBUG-111994
Fixes: QTBUG-112136
Co-authored-by: Peng Wu <alexepico@gmail.com>
Change-Id: Ic598d69a1e76109958fafa1226ea927656092319
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

3 files changed, 83 insertions, 22 deletions

diff --git a/src/gui/text/freetype/qfontengine_ft.cpp b/src/gui/text/freetype/qfontengine_ft.cpp
index 66a46d18cd..3d41cfda0a 100644
--- a/src/gui/text/freetype/qfontengine_ft.cpp
+++ b/src/gui/text/freetype/qfontengine_ft.cpp
@@ -278,6 +278,13 @@ QFreetypeFace *QFreetypeFace::getFace(const QFontEngine::FaceId &face_id,
         }
 #endif
         newFreetype->face = face;
+        newFreetype->mm_var = nullptr;
+        if (FT_IS_NAMED_INSTANCE(newFreetype->face)) {
+            FT_Error ftresult;
+            ftresult = FT_Get_MM_Var(face, &newFreetype->mm_var);
+            if (ftresult != FT_Err_Ok)
+                newFreetype->mm_var = nullptr;
+        }
 
         newFreetype->ref.storeRelaxed(1);
         newFreetype->xsize = 0;
@@ -351,6 +358,9 @@ QFreetypeFace *QFreetypeFace::getFace(const QFontEngine::FaceId &face_id,
 void QFreetypeFace::cleanup()
 {
     hbFace.reset();
+    if (mm_var && face && face->glyph)
+        FT_Done_MM_Var(face->glyph->library, mm_var);
+    mm_var = nullptr;
     FT_Done_Face(face);
     face = nullptr;
 }
@@ -818,16 +828,13 @@ bool QFontEngineFT::init(FaceId faceId, bool antialias, GlyphFormat format,
 
 static void dont_delete(void*) {}
 
-static FT_UShort calculateActualWeight(FT_Face face, QFontEngine::FaceId faceId)
+static FT_UShort calculateActualWeight(QFreetypeFace *freetypeFace, FT_Face face, QFontEngine::FaceId faceId)
 {
-    if (faceId.instanceIndex >= 0) {
-        FT_MM_Var *var = nullptr;
-        FT_Get_MM_Var(face, &var);
-        if (var != nullptr && FT_UInt(faceId.instanceIndex) < var->num_namedstyles) {
-            for (FT_UInt axis = 0; axis < var->num_axis; ++axis) {
-                if (var->axis[axis].tag == QFont::Tag("wght").value()) {
-                    return var->namedstyle[faceId.instanceIndex].coords[axis] >> 16;
-                }
+    FT_MM_Var *var = freetypeFace->mm_var;
+    if (var != nullptr && faceId.instanceIndex >= 0 && FT_UInt(faceId.instanceIndex) < var->num_namedstyles) {
+        for (FT_UInt axis = 0; axis < var->num_axis; ++axis) {
+            if (var->axis[axis].tag == QFont::Tag("wght").value()) {
+                return var->namedstyle[faceId.instanceIndex].coords[axis] >> 16;
             }
         }
     }
@@ -838,16 +845,13 @@ static FT_UShort calculateActualWeight(FT_Face face, QFontEngine::FaceId faceId)
     return 700;
 }
 
-static bool calculateActualItalic(FT_Face face, QFontEngine::FaceId faceId)
+static bool calculateActualItalic(QFreetypeFace *freetypeFace, FT_Face face, QFontEngine::FaceId faceId)
 {
-    if (faceId.instanceIndex >= 0) {
-        FT_MM_Var *var = nullptr;
-        FT_Get_MM_Var(face, &var);
-        if (var != nullptr && FT_UInt(faceId.instanceIndex) < var->num_namedstyles) {
-            for (FT_UInt axis = 0; axis < var->num_axis; ++axis) {
-                if (var->axis[axis].tag == QFont::Tag("ital").value()) {
-                    return (var->namedstyle[faceId.instanceIndex].coords[axis] >> 16) == 1;
-                }
+    FT_MM_Var *var = freetypeFace->mm_var;
+    if (var != nullptr && faceId.instanceIndex >= 0 && FT_UInt(faceId.instanceIndex) < var->num_namedstyles) {
+        for (FT_UInt axis = 0; axis < var->num_axis; ++axis) {
+            if (var->axis[axis].tag == QFont::Tag("ital").value()) {
+                return (var->namedstyle[faceId.instanceIndex].coords[axis] >> 16) == 1;
             }
         }
     }
@@ -886,7 +890,7 @@ bool QFontEngineFT::init(FaceId faceId, bool antialias, GlyphFormat format,
     FT_Face face = lockFace();
 
     if (FT_IS_SCALABLE(face)) {
-        bool isItalic = calculateActualItalic(face, faceId);
+        bool isItalic = calculateActualItalic(freetype, face, faceId);
         bool fake_oblique = (fontDef.style != QFont::StyleNormal) && !isItalic && !qEnvironmentVariableIsSet("QT_NO_SYNTHESIZED_ITALIC");
         if (fake_oblique)
             obliquen = true;
@@ -894,7 +898,7 @@ bool QFontEngineFT::init(FaceId faceId, bool antialias, GlyphFormat format,
         freetype->matrix = matrix;
         // fake bold
         if ((fontDef.weight >= QFont::Bold) && !(face->style_flags & FT_STYLE_FLAG_BOLD) && !FT_IS_FIXED_WIDTH(face)  && !qEnvironmentVariableIsSet("QT_NO_SYNTHESIZED_BOLD")) {
-            FT_UShort actualWeight = calculateActualWeight(face, faceId);
+            FT_UShort actualWeight = calculateActualWeight(freetype, face, faceId);
             if (actualWeight < 700 &&
                 (fontDef.pixelSize < 64 || qEnvironmentVariableIsSet("QT_NO_SYNTHESIZED_BOLD_LIMIT"))) {
                 embolden = true;
diff --git a/src/gui/text/freetype/qfontengine_ft_p.h b/src/gui/text/freetype/qfontengine_ft_p.h
index b6315a37d3..9245a271ad 100644
--- a/src/gui/text/freetype/qfontengine_ft_p.h
+++ b/src/gui/text/freetype/qfontengine_ft_p.h
@@ -19,6 +19,7 @@
 
 #include <ft2build.h>
 #include FT_FREETYPE_H
+#include FT_MULTIPLE_MASTERS_H
 
 
 #ifndef Q_OS_WIN
@@ -62,6 +63,7 @@ public:
     }
 
     FT_Face face;
+    FT_MM_Var *mm_var;
     int xsize; // 26.6
     int ysize; // 26.6
     FT_Matrix matrix;
diff --git a/src/gui/text/unix/qfontconfigdatabase.cpp b/src/gui/text/unix/qfontconfigdatabase.cpp
index a0b1abd14a..46e8f5724a 100644
--- a/src/gui/text/unix/qfontconfigdatabase.cpp
+++ b/src/gui/text/unix/qfontconfigdatabase.cpp
@@ -575,6 +575,12 @@ void QFontconfigDatabase::populateFontDatabase()
             FcObjectSetAdd(os, *p);
             ++p;
         }
+
+#ifdef FC_VARIABLE
+        /* Support the named instance of Variable Fonts. */
+        FcPatternAddBool(pattern, FC_VARIABLE, FcFalse);
+#endif
+
         fonts = FcFontList(nullptr, pattern, os);
         FcObjectSetDestroy(os);
         FcPatternDestroy(pattern);
@@ -974,6 +980,7 @@ void QFontconfigDatabase::setupFontEngine(QFontEngineFT *engine, const QFontDef
     QFontEngine::GlyphFormat format;
     // try and get the pattern
     FcPattern *pattern = FcPatternCreate();
+    FcPattern *match = nullptr;
 
     FcValue value;
     value.type = FcTypeString;
@@ -992,7 +999,7 @@ void QFontconfigDatabase::setupFontEngine(QFontEngineFT *engine, const QFontDef
         FcPatternAdd(pattern,FC_INDEX,value,true);
     }
 
-    if (fontDef.pixelSize > 0.1)
+    if (!qFuzzyIsNull(fontDef.pixelSize))
         FcPatternAddDouble(pattern, FC_PIXEL_SIZE, fontDef.pixelSize);
 
     FcResult result;
@@ -1000,7 +1007,55 @@ void QFontconfigDatabase::setupFontEngine(QFontEngineFT *engine, const QFontDef
     FcConfigSubstitute(nullptr, pattern, FcMatchPattern);
     FcDefaultSubstitute(pattern);
 
-    FcPattern *match = FcFontMatch(nullptr, pattern, &result);
+#ifdef FC_VARIABLE
+    if (!fid.filename.isEmpty()) {
+        // FC_INDEX is ignored during processing in FcFontMatch.
+        // So iterate FcPatterns directly and find it out.
+        FcFontSet *fcsets[2], *fcfs;
+
+        fcsets[0] = FcConfigGetFonts(nullptr, FcSetSystem);
+        fcsets[1] = FcConfigGetFonts(nullptr, FcSetApplication);
+        for (int nset = 0; nset < 2; nset++) {
+            fcfs = fcsets[nset];
+            if (fcfs == nullptr)
+                continue;
+            for (int fnum = 0; fnum < fcfs->nfont; fnum++) {
+                FcPattern *fcpat = fcfs->fonts[fnum];
+                FcChar8 *fcfile;
+                FcBool variable;
+                double fcpixelsize;
+                int fcindex;
+
+                // Skip the variable font itself, only to use the named instances and normal fonts here
+                if (FcPatternGetBool(fcpat, FC_VARIABLE, 0, &variable) == FcResultMatch &&
+                    variable == FcTrue)
+                    continue;
+
+                if (!qFuzzyIsNull(fontDef.pixelSize)) {
+                    if (FcPatternGetDouble(fcpat, FC_PIXEL_SIZE, 0, &fcpixelsize) == FcResultMatch &&
+                        fontDef.pixelSize != fcpixelsize)
+                    continue;
+                }
+
+                if (FcPatternGetString(fcpat, FC_FILE, 0, &fcfile) == FcResultMatch &&
+                    FcPatternGetInteger(fcpat, FC_INDEX, 0, &fcindex) == FcResultMatch) {
+                    QByteArray f = QByteArray::fromRawData((const char *)fcfile,
+                                                           qstrlen((const char *)fcfile));
+                    if (f == fid.filename && fcindex == fid.index) {
+                        // We found it.
+                        match = FcFontRenderPrepare(nullptr, pattern, fcpat);
+                        goto bail;
+                    }
+                }
+            }
+        }
+    }
+bail:
+#endif
+
+    if (!match)
+        match = FcFontMatch(nullptr, pattern, &result);
+
     if (match) {
         engine->setDefaultHintStyle(defaultHintStyleFromMatch((QFont::HintingPreference)fontDef.hintingPreference, match, useXftConf));