This is quite a complex method that can only be used when the selection mode is set to GTK_SELECTION_EXTENDED. It duplicates and resets the focus row (i.e. the row that is marked as selected) and highlights all the items between that and the anchor item. It has different behaviours depending on whether or not the list has keyboard grab, so that putting it into a callback function does not have the same results as calling it from the main loop.

Selection of all the items in the highlighted range requires that scroll_vertical() is also set appropriately.

In general, calling the extend_selection() method will only select the last row with focus. It needs to have toggle_add_mode() set in order to do this when scroll_vertical() is set after the list widget has grab.

As with scroll_vertical() , this method's position parameter is used only when the GtkScrollType value is set to GTK_SCROLL_JUMP, and represents a percentage of the area covered by the scroll. The final parameter negates the method's functionality completely if set to false.