diff -pruN qtbase-everywhere-src-5.15.8.orig/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp qtbase-everywhere-src-5.15.8/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp
--- qtbase-everywhere-src-5.15.8.orig/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp	2023-03-24 14:40:24.844713011 +0900
+++ qtbase-everywhere-src-5.15.8/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp	2023-03-24 21:22:35.466115667 +0900
@@ -954,6 +954,7 @@ void QFontconfigDatabase::setupFontEngin
     QFontEngine::GlyphFormat format;
     // try and get the pattern
     FcPattern *pattern = FcPatternCreate();
+    FcPattern *match = NULL;
 
     FcValue value;
     value.type = FcTypeString;
@@ -980,7 +981,41 @@ void QFontconfigDatabase::setupFontEngin
     FcConfigSubstitute(nullptr, pattern, FcMatchPattern);
     FcDefaultSubstitute(pattern);
 
-    FcPattern *match = FcFontMatch(nullptr, pattern, &result);
+    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];
+            for (int fnum = 0; fnum < fcfs->nfont; fnum++) {
+                FcPattern *fcpat = fcfs->fonts[fnum];
+                FcChar8 *fcfile;
+                FcBool variable;
+                int fcindex;
+
+                // FIXME: Ignore a FcPattern which has variable=true at this point.
+                if (FcPatternGetBool(fcpat, FC_VARIABLE, 0, &variable) == FcResultMatch &&
+                    variable == FcTrue)
+                    continue;
+                if (FcPatternGetString(fcpat, FC_FILE, 0, &fcfile) == FcResultMatch &&
+                    FcPatternGetInteger(fcpat, FC_INDEX, 0, &fcindex) == FcResultMatch) {
+                    QByteArray f = QByteArray::fromRawData((const char *)fcfile,
+                                                           strlen((const char *)fcfile));
+                    if (f == fid.filename && fcindex == fid.index) {
+                        // We found it.
+                        match = FcFontRenderPrepare(nullptr, pattern, fcpat);
+                        goto bail;
+                    }
+                }
+            }
+        }
+    }
+bail:
+    if (!match)
+        match = FcFontMatch(nullptr, pattern, &result);
     if (match) {
         engine->setDefaultHintStyle(defaultHintStyleFromMatch((QFont::HintingPreference)fontDef.hintingPreference, match, useXftConf));
 
diff -pruN qtbase-everywhere-src-5.15.8.orig/src/platformsupport/fontdatabases/freetype/qfontengine_ft.cpp qtbase-everywhere-src-5.15.8/src/platformsupport/fontdatabases/freetype/qfontengine_ft.cpp
--- qtbase-everywhere-src-5.15.8.orig/src/platformsupport/fontdatabases/freetype/qfontengine_ft.cpp	2022-11-11 16:29:17.000000000 +0900
+++ qtbase-everywhere-src-5.15.8/src/platformsupport/fontdatabases/freetype/qfontengine_ft.cpp	2023-03-24 23:03:02.165756803 +0900
@@ -68,6 +68,7 @@
 #include FT_GLYPH_H
 #include FT_MODULE_H
 #include FT_LCD_FILTER_H
+#include FT_MULTIPLE_MASTERS_H
 
 #if defined(FT_CONFIG_OPTIONS_H)
 #include FT_CONFIG_OPTIONS_H
@@ -740,6 +741,29 @@ bool QFontEngineFT::init(FaceId faceId,
     freetype->computeSize(fontDef, &xsize, &ysize, &defaultGlyphSet.outline_drawing, &scalableBitmapScaleFactor);
 
     FT_Face face = lockFace();
+    FT_MM_Var *master = nullptr;
+    FT_Error ftresult;
+    double weight_mult = 1.0;
+
+    ftresult = FT_Get_MM_Var(face, &master);
+    if (face_id.index >> 16 && ftresult == FT_Err_Ok) {
+        if ((face_id.index >> 16) - 1 < master->num_namedstyles) {
+            // Pull out weight and width from named-instance.
+            FT_Var_Named_Style *instance = &master->namedstyle[(face_id.index >> 16) - 1];
+
+            for (unsigned int i = 0; i < master->num_axis; i++) {
+                double value = instance->coords[i] / (double) (1U << 16);
+                double default_value = master->axis[i].def / (double) (1U << 16);
+                double mult = default_value ? value / default_value : 1;
+
+                switch (master->axis[i].tag) {
+                case FT_MAKE_TAG('w', 'g', 'h', 't'):
+                    weight_mult = mult;
+                    break;
+                }
+            }
+        }
+    }
 
     if (FT_IS_SCALABLE(face)) {
         bool fake_oblique = (fontDef.style != QFont::StyleNormal) && !(face->style_flags & FT_STYLE_FLAG_ITALIC) && !qEnvironmentVariableIsSet("QT_NO_SYNTHESIZED_ITALIC");
@@ -750,7 +774,7 @@ bool QFontEngineFT::init(FaceId faceId,
         // fake bold
         if ((fontDef.weight >= QFont::Bold) && !(face->style_flags & FT_STYLE_FLAG_BOLD) && !FT_IS_FIXED_WIDTH(face) && !qEnvironmentVariableIsSet("QT_NO_SYNTHESIZED_BOLD")) {
             if (const TT_OS2 *os2 = reinterpret_cast<const TT_OS2 *>(FT_Get_Sfnt_Table(face, ft_sfnt_os2))) {
-                if (os2->usWeightClass < 700 && fontDef.pixelSize < 64)
+                if (os2->usWeightClass * weight_mult < 700 && fontDef.pixelSize < 64)
                     embolden = true;
             }
         }
@@ -829,6 +853,8 @@ bool QFontEngineFT::init(FaceId faceId,
     } else {
         Q_ASSERT(!face_);
     }
+    if (master && face->glyph)
+        FT_Done_MM_Var(face->glyph->library, master);
     // we share the HB face in QFreeTypeFace, so do not let ~QFontEngine() destroy it
     face_ = Holder(freetype->hbFace.get(), dont_delete);