There's "mainwin", a window containing a reorderable treeview, and it has a
signal handler connected to row-activated on the treeview.

Creating a dialog in that handler, with another handler connected to the
dialogs response signal, and in the first handler doing just
gtk_widget_show(_all) on the dialog instead of using dialog_run and still
in that handler setting mainwin insensitive; and closing the dialog in it's
response handler while setting mainwin sensitive again, causes the mouse
pointer to be in row drag mode when it gets over mainwin again.

Making the treeview not reorderable also makes the drag mode be gone, for
fairly obvious reasons.