Re: Application of preconditions for status transitions from data input in views

[Markus Elfring <Markus Elfring web de>]

Hello!

The documentation for the member function "append_column_editable" provides the
following information.
http://developer.gnome.org/gtkmm/3.2/classGtk_1_1TreeView.html#a83d537226bbbb054aa792c03248e619f

"Appends a View column with the appropriate CellRenderer for the Model column.

The compiler will attempt to instantiate appropriate template code to
automatically store user changes in the model. To intercept the user's change
and implement non-default logic, or if the compiler can't instantiate
appropriate code for your model type, you could use append_column() and connect
a signal handler to the CellRenderer."

Now I have got an use case where I appreciate some effects from this automatic
setting. But I would like to apply input validation before model attributes will
be actually changed.

I imagine that I need something from the model software infrastructure to
intercept a write request to an attribute so that it will become possible for an
enquiry in the (graphical) user interface if the desired change will need
additional information. How do you get the corresponding view to display a
required confirmation dialogue?

Regards,
Markus