qfreetype: Fix caching of memory fonts

Make QFreetypeFace::getFace() not return the same font
face for all memory fonts.

QtFreetypeData has a cache which maps QFontEngine::FaceId
to QFreetypeFace instances. Each FaceId should then
have a unique hash value, which is accomplished by
by hashing the font file name and a stored uuid.

However, we were not setting the uuid in all cases,
which means that in-memory fonts (which do not have
a file name) would hash identically.

Fix this by setting the uuid to a value based on the
address of the FontFile, which should be unique.

Pick-to: 6.7
Change-Id: I45de37b512fb666c26490551c831c0db824b5f35
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

src/gui/text/freetype/qfreetypefontdatabase.cpp

@@ -11,6 +11,7 @@
 #include <QtCore/QDir>
 #include <QtCore/QtEndian>
 #include <QtCore/QLoggingCategory>
+#include <QtCore/QUuid>
 
 #undef QT_NO_FREETYPE
 #include "qfontengine_ft_p.h"
@@ -64,6 +65,14 @@ QFontEngine *QFreeTypeFontDatabase::fontEngine(const QFontDef &fontDef, void *us
     faceId.instanceIndex = fontfile->instanceIndex;
     faceId.variableAxes = fontDef.variableAxisValues;
 
+    // Make sure the FaceId compares uniquely in cases where a
+    // file name is not provided.
+    if (faceId.filename.isEmpty()) {
+        QUuid::Id128Bytes id{};
+        memcpy(&id, &usrPtr, sizeof(usrPtr));
+        faceId.uuid = QUuid(id).toByteArray();
+    }
+
     return QFontEngineFT::create(fontDef, faceId, fontfile->data);
 }