As with CList, the Tree type has a selection field, and
it is possible to control the behaviour of the tree (somewhat) by
setting the selection type using:
void gtk_tree_set_selection_mode( GtkTree *tree,
GtkSelectionMode mode ); |
The semantics associated with the various selection modes are
described in the section on the CList widget. As with the CList
widget, the "select_child", "unselect_child" (not really - see Signals below for an explanation),
and "selection_changed" signals are emitted when list items are
selected or unselected. However, in order to take advantage of these
signals, you need to know which Tree widget they will be
emitted by, and where to find the list of selected items.
This is a source of potential confusion. The best way to explain this
is that though all Tree widgets are created equal, some are more equal
than others. All Tree widgets have their own X window, and can
therefore receive events such as mouse clicks (if their TreeItems or
their children don't catch them first!). However, to make
GTK_SELECTION_SINGLE and GTK_SELECTION_BROWSE selection
types behave in a sane manner, the list of selected items is specific
to the topmost Tree widget in a hierarchy, known as the "root tree".
Thus, accessing the selection field directly in an arbitrary
Tree widget is not a good idea unless you know it's the root
tree. Instead, use the GTK_TREE_SELECTION (Tree) macro, which
gives the root tree's selection list as a GList pointer. Of course,
this list can include items that are not in the subtree in question if
the selection type is GTK_SELECTION_MULTIPLE.
Finally, the "select_child" (and "unselect_child", in theory) signals
are emitted by all trees, but the "selection_changed" signal is only
emitted by the root tree. Consequently, if you want to handle the
"select_child" signal for a tree and all its subtrees, you will have
to call gtk_signal_connect() for every subtree.
