If a QLineEdit has an input mask containing both optional and compulsory characters (which have mask A, N, X, 9, D, H, B) it would be nice if the compulsory characters are entered in first when the widget is filled via setText(const QString&) .

The current behavior does not do this.

Consider the case of creating a simple IP address filter, such as "009.009.009.009;0"
If it is populated with "1.2.3.4" via setText().
The result is "100.200.300.400"
which is not optimal.