Switch track compositing to frei0r.cairoblend by default instead of qtblend.

Slightly slower but fixes scaling issues like #1216

src/doc/documentvalidator.cpp

@@ -2218,10 +2218,10 @@ bool DocumentValidator::checkMovit()
     bool hasWB = EffectsRepository::get()->exists(QStringLiteral("frei0r.colgate"));
     bool hasBlur = EffectsRepository::get()->exists(QStringLiteral("frei0r.IIRblur"));
     QString compositeTrans;
-    if (TransitionsRepository::get()->exists(QStringLiteral("qtblend"))) {
-        compositeTrans = QStringLiteral("qtblend");
-    } else if (TransitionsRepository::get()->exists(QStringLiteral("frei0r.cairoblend"))) {
+    if (TransitionsRepository::get()->exists(QStringLiteral("frei0r.cairoblend"))) {
         compositeTrans = QStringLiteral("frei0r.cairoblend");
+    } else if (TransitionsRepository::get()->exists(QStringLiteral("qtblend"))) {
+        compositeTrans = QStringLiteral("qtblend");
     }
 
     // Parse all effects in document

src/transitions/transitionsrepository.cpp

@@ -158,12 +158,12 @@ const QString TransitionsRepository::getCompositingTransition()
     if (KdenliveSettings::gpu_accel()) {
         return QStringLiteral("movit.overlay");
     }
-    if (exists(QStringLiteral("qtblend"))) {
-        return QStringLiteral("qtblend");
-    }
     if (exists(QStringLiteral("frei0r.cairoblend"))) {
         return QStringLiteral("frei0r.cairoblend");
     }
+    if (exists(QStringLiteral("qtblend"))) {
+        return QStringLiteral("qtblend");
+    }
     if (exists(QStringLiteral("composite"))) {
         return QStringLiteral("composite");
     }