Reverse fontconfig dominance logic

This changes four things:
1. The detection of Xft using platforms is now reversed assumed true,
unless the desktop environment is traditionally Qt based.
2. When Xft using platforms are detected the Xft settings win over
fontconfig settings.
3. On other platforms, Xft settings can still be used as a fallback if
no fontconfig settings are found.
4. In case of no fontconfig match Xft settings are now applied, where
before they would never be.

Fixes: QTBUG-43745
Change-Id: I52372a6e2315441668eaf384046514fd6653e64a
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

1 files changed, 62 insertions, 40 deletions

diff --git a/src/gui/text/unix/qfontconfigdatabase.cpp b/src/gui/text/unix/qfontconfigdatabase.cpp
index 975a583220..d607d38235 100644
--- a/src/gui/text/unix/qfontconfigdatabase.cpp
+++ b/src/gui/text/unix/qfontconfigdatabase.cpp
@@ -642,7 +642,7 @@ QFontEngineMulti *QFontconfigDatabase::fontEngineMulti(QFontEngine *fontEngine,
 }
 
 namespace {
-QFontEngine::HintStyle defaultHintStyleFromMatch(QFont::HintingPreference hintingPreference, FcPattern *match, bool useXftConf)
+QFontEngine::HintStyle defaultHintStyleFromMatch(QFont::HintingPreference hintingPreference, FcPattern *match, bool preferXftConf)
 {
     switch (hintingPreference) {
     case QFont::PreferNoHinting:
@@ -658,6 +658,13 @@ QFontEngine::HintStyle defaultHintStyleFromMatch(QFont::HintingPreference hintin
     if (isDprScaling())
         return QFontEngine::HintNone;
 
+    void *hintStyleResource =
+            QGuiApplication::platformNativeInterface()->nativeResourceForScreen("hintstyle",
+                                                                                QGuiApplication::primaryScreen());
+    int xftHintStyle =  int(reinterpret_cast<qintptr>(hintStyleResource));
+    if (preferXftConf && xftHintStyle > 0)
+        return QFontEngine::HintStyle(xftHintStyle - 1);
+
     int hint_style = 0;
     if (FcPatternGetInteger (match, FC_HINT_STYLE, 0, &hint_style) == FcResultMatch) {
         switch (hint_style) {
@@ -674,21 +681,21 @@ QFontEngine::HintStyle defaultHintStyleFromMatch(QFont::HintingPreference hintin
             break;
         }
     }
-
-    if (useXftConf) {
-        void *hintStyleResource =
-                QGuiApplication::platformNativeInterface()->nativeResourceForScreen("hintstyle",
-                                                                                    QGuiApplication::primaryScreen());
-        int hintStyle = int(reinterpret_cast<qintptr>(hintStyleResource));
-        if (hintStyle > 0)
-            return QFontEngine::HintStyle(hintStyle - 1);
-    }
+    if (xftHintStyle > 0)
+        return QFontEngine::HintStyle(xftHintStyle - 1);
 
     return QFontEngine::HintFull;
 }
 
-QFontEngine::SubpixelAntialiasingType subpixelTypeFromMatch(FcPattern *match, bool useXftConf)
+QFontEngine::SubpixelAntialiasingType subpixelTypeFromMatch(FcPattern *match, bool preferXftConf)
 {
+    void *subpixelTypeResource =
+            QGuiApplication::platformNativeInterface()->nativeResourceForScreen("subpixeltype",
+                                                                                QGuiApplication::primaryScreen());
+    int xftSubpixelType = int(reinterpret_cast<qintptr>(subpixelTypeResource));
+    if (preferXftConf && xftSubpixelType > 0)
+        return QFontEngine::SubpixelAntialiasingType(xftSubpixelType - 1);
+
     int subpixel = FC_RGBA_UNKNOWN;
     if (FcPatternGetInteger(match, FC_RGBA, 0, &subpixel) == FcResultMatch) {
         switch (subpixel) {
@@ -709,14 +716,8 @@ QFontEngine::SubpixelAntialiasingType subpixelTypeFromMatch(FcPattern *match, bo
         }
     }
 
-    if (useXftConf) {
-        void *subpixelTypeResource =
-                QGuiApplication::platformNativeInterface()->nativeResourceForScreen("subpixeltype",
-                                                                                    QGuiApplication::primaryScreen());
-        int subpixelType = int(reinterpret_cast<qintptr>(subpixelTypeResource));
-        if (subpixelType > 0)
-            return QFontEngine::SubpixelAntialiasingType(subpixelType - 1);
-    }
+    if (xftSubpixelType > 0)
+        return QFontEngine::SubpixelAntialiasingType(xftSubpixelType - 1);
 
     return QFontEngine::Subpixel_None;
 }
@@ -965,20 +966,11 @@ void QFontconfigDatabase::setupFontEngine(QFontEngineFT *engine, const QFontDef
     bool forcedAntialiasSetting = !antialias || isDprScaling();
 
     const QPlatformServices *services = QGuiApplicationPrivate::platformIntegration()->services();
-    bool useXftConf = false;
+    bool preferXftConf = false;
 
     if (services) {
         const QList<QByteArray> desktopEnv = services->desktopEnvironment().split(':');
-        useXftConf = desktopEnv.contains("GNOME") || desktopEnv.contains("UNITY") || desktopEnv.contains("XFCE");
-    }
-
-    if (useXftConf && !forcedAntialiasSetting) {
-        void *antialiasResource =
-                QGuiApplication::platformNativeInterface()->nativeResourceForScreen("antialiasingEnabled",
-                                                                                    QGuiApplication::primaryScreen());
-        int antialiasingEnabled = int(reinterpret_cast<qintptr>(antialiasResource));
-        if (antialiasingEnabled > 0)
-            antialias = antialiasingEnabled - 1;
+        preferXftConf = !(desktopEnv.contains("KDE") || desktopEnv.contains("LXQT") || desktopEnv.contains("UKUI"));
     }
 
     QFontEngine::GlyphFormat format;
@@ -1060,8 +1052,19 @@ bail:
     if (!match)
         match = FcFontMatch(nullptr, pattern, &result);
 
+    int xftAntialias = 0;
+    if (!forcedAntialiasSetting) {
+        void *antialiasResource =
+                QGuiApplication::platformNativeInterface()->nativeResourceForScreen("antialiasingEnabled",
+                                                                                    QGuiApplication::primaryScreen());
+        xftAntialias = int(reinterpret_cast<qintptr>(antialiasResource));
+        if ((preferXftConf || !match) && xftAntialias > 0) {
+            antialias = xftAntialias - 1;
+            forcedAntialiasSetting = true;
+        }
+    }
     if (match) {
-        engine->setDefaultHintStyle(defaultHintStyleFromMatch((QFont::HintingPreference)fontDef.hintingPreference, match, useXftConf));
+        engine->setDefaultHintStyle(defaultHintStyleFromMatch((QFont::HintingPreference)fontDef.hintingPreference, match, preferXftConf));
 
         FcBool fc_autohint;
         if (FcPatternGetBool(match, FC_AUTOHINT,0, &fc_autohint) == FcResultMatch)
@@ -1082,18 +1085,37 @@ bail:
         if (antialias) {
             QFontEngine::SubpixelAntialiasingType subpixelType = QFontEngine::Subpixel_None;
             if (!(fontDef.styleStrategy & QFont::NoSubpixelAntialias))
-                subpixelType = subpixelTypeFromMatch(match, useXftConf);
+                subpixelType = subpixelTypeFromMatch(match, preferXftConf);
             engine->subpixelType = subpixelType;
-
-            format = (subpixelType == QFontEngine::Subpixel_None)
-                    ? QFontEngine::Format_A8
-                    : QFontEngine::Format_A32;
-        } else
-            format = QFontEngine::Format_Mono;
+        }
 
         FcPatternDestroy(match);
-    } else
-        format = antialias ? QFontEngine::Format_A8 : QFontEngine::Format_Mono;
+    } else {
+        void *hintStyleResource =
+                QGuiApplication::platformNativeInterface()->nativeResourceForScreen("hintstyle",
+                                                                                    QGuiApplication::primaryScreen());
+        int xftHintStyle =  int(reinterpret_cast<qintptr>(hintStyleResource));
+        if (xftHintStyle > 0)
+            engine->setDefaultHintStyle(QFontEngine::HintStyle(xftHintStyle - 1));
+        if (antialias) {
+            engine->subpixelType = QFontEngine::Subpixel_None;
+            if (!(fontDef.styleStrategy & QFont::NoSubpixelAntialias)) {
+                void *subpixelTypeResource =
+                        QGuiApplication::platformNativeInterface()->nativeResourceForScreen("subpixeltype",
+                                                                                            QGuiApplication::primaryScreen());
+                int xftSubpixelType = int(reinterpret_cast<qintptr>(subpixelTypeResource));
+                if (xftSubpixelType > 1)
+                    engine->subpixelType = QFontEngine::SubpixelAntialiasingType(xftSubpixelType - 1);
+            }
+        }
+    }
+    if (antialias) {
+        format = (engine->subpixelType == QFontEngine::Subpixel_None)
+                ? QFontEngine::Format_A8
+                : QFontEngine::Format_A32;
+    } else {
+        format = QFontEngine::Format_Mono;
+    }
 
     FcPatternDestroy(pattern);