qBound seem to accept only function attributes that are same type.

There's multiple places where constants are given without type. Default type is double precission float(double). Fix could be to change constant to have float specifier ie. 0.0f. Or by casting, like it's done in most of places.

-    size = qBound(0.0, size, 1.0);
+    size = qBound(qreal(0.0), size, qreal(1.0));