QFontDatabase (Windows): Sanitize font requests early

After the windows font engine was no longer marking everything as
scalable we started limiting the font size of requests to the maximum
of Courier when it was requested. This was a regression from 5.8 and not
in agreement with our documentation.

The problem is that we would only make the switch from Courier to
Courier New after having already gone through the foundry-lookup and
found a closest-available font size for Courier.

With this sanitization step in the backend we can make these changes
early enough that we haven't yet adjusted e.g. the font size.

Pick-to: 6.2 5.15
Fixes: QTBUG-58995
Change-Id: I319e93e6b78c7c3c5539964ac5ab4e05f8902ab6
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

3 files changed, 34 insertions, 11 deletions

diff --git a/src/gui/text/qfontdatabase.cpp b/src/gui/text/qfontdatabase.cpp
index 887fb8eb2e..e2898b078c 100644
--- a/src/gui/text/qfontdatabase.cpp
+++ b/src/gui/text/qfontdatabase.cpp
@@ -62,6 +62,10 @@
 
 #include <qtgui_tracepoints_p.h>
 
+#ifdef Q_OS_WIN
+#include <QtGui/private/qwindowsfontdatabasebase_p.h>
+#endif
+
 QT_BEGIN_NAMESPACE
 
 Q_LOGGING_CATEGORY(lcFontDb, "qt.text.font.db")
@@ -2350,7 +2354,7 @@ bool QFontDatabase::removeAllApplicationFonts()
 /*!
     \internal
 */
-QFontEngine *QFontDatabasePrivate::findFont(const QFontDef &request,
+QFontEngine *QFontDatabasePrivate::findFont(const QFontDef &req,
                                             int script,
                                             bool preferScriptOverFamily)
 {
@@ -2361,6 +2365,14 @@ QFontEngine *QFontDatabasePrivate::findFont(const QFontDef &request,
 
     QFontEngine *engine;
 
+#ifdef Q_OS_WIN
+    const QFontDef request = static_cast<QWindowsFontDatabaseBase *>(
+                                     QGuiApplicationPrivate::platformIntegration()->fontDatabase())
+                                     ->sanitizeRequest(req);
+#else
+    const QFontDef &request = req;
+#endif
+
 #if defined(QT_BUILD_INTERNAL)
     // For testing purpose only, emulates an exact-matching monospace font
     if (qt_enable_test_font && request.families.first() == QLatin1String("__Qt__Box__Engine__")) {
diff --git a/src/gui/text/windows/qwindowsfontdatabasebase.cpp b/src/gui/text/windows/qwindowsfontdatabasebase.cpp
index 49586063b9..47ef300cfa 100644
--- a/src/gui/text/windows/qwindowsfontdatabasebase.cpp
+++ b/src/gui/text/windows/qwindowsfontdatabasebase.cpp
@@ -696,16 +696,6 @@ LOGFONT QWindowsFontDatabaseBase::fontDefToLOGFONT(const QFontDef &request, cons
         fam.truncate(LF_FACESIZE - 1);
     }
 
-    if (fam.isEmpty())
-        fam = QStringLiteral("MS Sans Serif");
-
-    if (fam == QLatin1String("MS Sans Serif")
-        && (request.style == QFont::StyleItalic || (-lf.lfHeight > 18 && -lf.lfHeight != 24))) {
-        fam = QStringLiteral("Arial"); // MS Sans Serif has bearing problems in italic, and does not scale
-    }
-    if (fam == QLatin1String("Courier") && !(request.styleStrategy & QFont::PreferBitmap))
-        fam = QStringLiteral("Courier New");
-
     memcpy(lf.lfFaceName, fam.utf16(), fam.size() * sizeof(wchar_t));
 
     return lf;
@@ -947,4 +937,23 @@ QStringList QWindowsFontDatabaseBase::extraTryFontsForFamily(const QString &fami
     return result;
 }
 
+QFontDef QWindowsFontDatabaseBase::sanitizeRequest(QFontDef request) const
+{
+    QFontDef req = request;
+    const QString fam = request.families.front();
+    if (fam.isEmpty())
+        req.families[0] = QStringLiteral("MS Sans Serif");
+
+    if (fam == QLatin1String("MS Sans Serif")) {
+        int height = -qRound(request.pixelSize);
+        // MS Sans Serif has bearing problems in italic, and does not scale
+        if (request.style == QFont::StyleItalic || (height > 18 && height != 24))
+            req.families[0] = QStringLiteral("Arial");
+    }
+
+    if (!(request.styleStrategy & QFont::StyleStrategy::PreferBitmap) && fam == u"Courier")
+        req.families[0] = QStringLiteral("Courier New");
+    return req;
+}
+
 QT_END_NAMESPACE
diff --git a/src/gui/text/windows/qwindowsfontdatabasebase_p.h b/src/gui/text/windows/qwindowsfontdatabasebase_p.h
index 873912f8ef..158991a796 100644
--- a/src/gui/text/windows/qwindowsfontdatabasebase_p.h
+++ b/src/gui/text/windows/qwindowsfontdatabasebase_p.h
@@ -122,6 +122,8 @@ public:
         QByteArray m_fontData;
     };
 
+    QFontDef sanitizeRequest(QFontDef request) const;
+
 protected:
 
 #if QT_CONFIG(directwrite)