The purpose of tree widgets is to display hierarchically-organized data. The GtkTree widget itself is a vertical container for widgets of type GtkTreeItem. GtkTree itself is not terribly different from GtkList - both are derived directly from GtkContainer, and the GtkContainer methods work in the same way on GtkTree widgets as on GtkList widgets. The difference is that GtkTree widgets can be nested within other GtkTree widgets. We'll see how to do this shortly.
The GtkTree widget has its own window, and defaults to a white background, as does GtkList. Also, most of the GtkTree methods work in the same way as the corresponding GtkList ones. However, GtkTree is not derived from GtkList, so you cannot use them interchangeably.
A GtkTree is created in the usual way, using:
GtkWidget *gtk_tree_new( void );
Like the GtkList widget, a GtkTree will simply keep growing as more items are added to it, as well as when subtrees are expanded. For this reason, they are almost always packed into a GtkScrolledWindow. You might want to use gtk_widget_set_usize() on the scrolled window to ensure that it is big enough to see the tree's items, as the default size for GtkScrolledWindow is quite small.
Now that you have a tree, you'll probably want to add some items to it. The Tree Item Widget below explains the gory details of GtkTreeItem. For now, it'll suffice to create one, using:
GtkWidget *gtk_tree_item_new_with_label( gchar *label );
You can then add it to the tree using one of the following (see Functions and Macros below for more options):
void gtk_tree_append( GtkTree *tree,
GtkWidget *tree_item );
void gtk_tree_prepend( GtkTree *tree,
GtkWidget *tree_item );
Note that you must add items to a GtkTree one at a time - there is no equivalent to gtk_list_*_items().
A subtree is created like any other GtkTree widget. A subtree is added to another tree beneath a tree item, using:
void gtk_tree_item_set_subtree( GtkTreeItem *tree_item,
GtkWidget *subtree );
You do not need to call gtk_widget_show() on a subtree before or after adding it to a GtkTreeItem. However, you must have added the GtkTreeItem in question to a parent tree before calling gtk_tree_item_set_subtree(). This is because, technically, the parent of the subtree is not the GtkTreeItem which "owns" it, but rather the GtkTree which holds that GtkTreeItem.
When you add a subtree to a GtkTreeItem, a plus or minus sign appears beside it, which the user can click on to "expand" or "collapse" it, meaning, to show or hide its subtree. GtkTreeItems are collapsed by default. Note that when you collapse a GtkTreeItem, any selected items in its subtree remain selected, which may not be what the user expects.
As with GtkList, the GtkTree 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 GtkList widget. As with the GtkList 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 GtkTree 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 GtkTree widgets are created equal, some are more equal than others. All GtkTree widgets have their own X window, and can therefore receive events such as mouse clicks (if their GtkTreeItems 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 GtkTree widget in a hierarchy, known as the "root tree".
Thus, accessing the selectionfield directly in an arbitrary
GtkTree 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.
The GtkTree's struct definition looks like this:
struct _GtkTree
{
GtkContainer container;
GList *children;
GtkTree* root_tree; /* owner of selection list */
GtkWidget* tree_owner;
GList *selection;
guint level;
guint indent_value;
guint current_indent;
guint selection_mode : 2;
guint view_mode : 1;
guint view_line : 1;
};
The perils associated with accessing the selection field
directly have already been mentioned. The other important fields of
the struct can also be accessed with handy macros or class functions.
GTK_TREE_IS_ROOT_TREE (Tree) returns a boolean value which indicates
whether a tree is the root tree in a GtkTree hierarchy, while
GTK_TREE_ROOT_TREE (Tree) returns the root tree, an object of type
GtkTree (so, remember to cast it using GTK_WIDGET (Tree) if you want
to use one of the gtk_widget_*() functions on it).
Instead of directly accessing the children field of a GtkTree widget, it's probably best to cast it using GTK_CONTAINER (Tree), and pass it to the gtk_container_children() function. This creates a duplicate of the original list, so it's advisable to free it up using g_list_free() after you're done with it, or to iterate on it destructively, like this:
children = gtk_container_children (GTK_CONTAINER (tree));
while (children) {
do_something_nice (GTK_TREE_ITEM (children->data));
children = g_list_remove_link (children, children);
}
The tree_owner field is defined only in subtrees, where it
points to the GtkTreeItem widget which holds the tree in question.
The level field indicates how deeply nested a particular tree
is; root trees have level 0, and each successive level of subtrees has
a level one greater than the parent level. This field is set only
after a GtkTree widget is actually mapped (i.e. drawn on the screen).
void selection_changed( GtkTree *tree );
This signal will be emitted whenever the selection field of a
GtkTree has changed. This happens when a child of the GtkTree is
selected or deselected.
void select_child( GtkTree *tree,
GtkWidget *child );
This signal is emitted when a child of the GtkTree is about to get selected. This happens on calls to gtk_tree_select_item(), gtk_tree_select_child(), on all button presses and calls to gtk_tree_item_toggle() and gtk_item_toggle(). It may sometimes be indirectly triggered on other occasions where children get added to or removed from the GtkTree.
void unselect_child (GtkTree *tree,
GtkWidget *child);
This signal is emitted when a child of the GtkTree is about to get deselected. As of GTK+ 1.0.4, this seems to only occur on calls to gtk_tree_unselect_item() or gtk_tree_unselect_child(), and perhaps on other occasions, but not when a button press deselects a child, nor on emission of the "toggle" signal by gtk_item_toggle().
guint gtk_tree_get_type( void );
Returns the `GtkTree' type identifier.
GtkWidget* gtk_tree_new( void );
Create a new GtkTree object. The new widget is returned as a pointer to a GtkWidget object. NULL is returned on failure.
void gtk_tree_append( GtkTree *tree,
GtkWidget *tree_item );
Append a tree item to a GtkTree.
void gtk_tree_prepend( GtkTree *tree,
GtkWidget *tree_item );
Prepend a tree item to a GtkTree.
void gtk_tree_insert( GtkTree *tree,
GtkWidget *tree_item,
gint position );
Insert a tree item into a GtkTree at the position in the list
specified by position.
void gtk_tree_remove_items( GtkTree *tree,
GList *items );
Remove a list of items (in the form of a GList *) from a GtkTree. Note that removing an item from a tree dereferences (and thus usually) destroys it and its subtree, if it has one, and all subtrees in that subtree. If you want to remove only one item, you can use gtk_container_remove().
void gtk_tree_clear_items( GtkTree *tree,
gint start,
gint end );
Remove the items from position start to position end
from a GtkTree. The same warning about dereferencing applies here, as
gtk_tree_clear_items() simply constructs a list and passes it to
gtk_tree_remove_items().
void gtk_tree_select_item( GtkTree *tree,
gint item );
Emits the "select_item" signal for the child at position
item, thus selecting the child (unless you unselect it in a
signal handler).
void gtk_tree_unselect_item( GtkTree *tree,
gint item );
Emits the "unselect_item" signal for the child at position
item, thus unselecting the child.
void gtk_tree_select_child( GtkTree *tree,
GtkWidget *tree_item );
Emits the "select_item" signal for the child tree_item, thus
selecting it.
void gtk_tree_unselect_child( GtkTree *tree,
GtkWidget *tree_item );
Emits the "unselect_item" signal for the child tree_item,
thus unselecting it.
gint gtk_tree_child_position( GtkTree *tree,
GtkWidget *child );
Returns the position in the tree of child, unless
child is not in the tree, in which case it returns -1.
void gtk_tree_set_selection_mode( GtkTree *tree,
GtkSelectionMode mode );
Sets the selection mode, which can be one of GTK_SELECTION_SINGLE (the default), GTK_SELECTION_BROWSE, GTK_SELECTION_MULTIPLE, or GTK_SELECTION_EXTENDED. This is only defined for root trees, which makes sense, since the root tree "owns" the selection. Setting it for subtrees has no effect at all; the value is simply ignored.
void gtk_tree_set_view_mode( GtkTree *tree,
GtkTreeViewMode mode );
Sets the "view mode", which can be either GTK_TREE_VIEW_LINE (the default) or GTK_TREE_VIEW_ITEM. The view mode propagates from a tree to its subtrees, and can't be set exclusively to a subtree (this is not exactly true - see the example code comments).
The term "view mode" is rather ambiguous - basically, it controls the way the highlight is drawn when one of a tree's children is selected. If it's GTK_TREE_VIEW_LINE, the entire GtkTreeItem widget is highlighted, while for GTK_TREE_VIEW_ITEM, only the child widget (i.e. usually the label) is highlighted.
void gtk_tree_set_view_lines( GtkTree *tree,
guint flag );
Controls whether connecting lines between tree items are drawn.
flag is either TRUE, in which case they are, or FALSE, in
which case they aren't.
GtkTree *GTK_TREE (gpointer obj);
Cast a generic pointer to `GtkTree *'.
GtkTreeClass *GTK_TREE_CLASS (gpointer class);
Cast a generic pointer to `GtkTreeClass*'.
gint GTK_IS_TREE (gpointer obj);
Determine if a generic pointer refers to a `GtkTree' object.
gint GTK_IS_ROOT_TREE (gpointer obj)
Determine if a generic pointer refers to a `GtkTree' object and is a root tree. Though this will accept any pointer, the results of passing it a pointer that does not refer to a GtkTree are undefined and possibly harmful.
GtkTree *GTK_TREE_ROOT_TREE (gpointer obj)
Return the root tree of a pointer to a `GtkTree' object. The above warning applies.
GList *GTK_TREE_SELECTION( gpointer obj)
Return the selection list of the root tree of a `GtkTree' object. The above warning applies here, too.
The GtkTreeItem widget, like GtkListItem, is derived from GtkItem,
which in turn is derived from GtkBin. Therefore, the item itself is a
generic container holding exactly one child widget, which can be of
any type. The GtkTreeItem widget has a number of extra fields, but
the only one we need be concerned with is the subtree field.
The definition for the GtkTreeItem struct looks like this:
struct _GtkTreeItem
{
GtkItem item;
GtkWidget *subtree;
GtkWidget *pixmaps_box;
GtkWidget *plus_pix_widget, *minus_pix_widget;
GList *pixmaps; /* pixmap node for this items color depth */
guint expanded : 1;
};
The pixmaps_box field is a GtkEventBox which catches clicks
on the plus/minus symbol which controls expansion and collapsing. The
pixmaps field points to an internal data structure. Since
you can always obtain the subtree of a GtkTreeItem in a (relatively)
type-safe manner with the GTK_TREE_ITEM_SUBTREE (Item) macro, it's
probably advisable never to touch the insides of a GtkTreeItem unless
you really know what you're doing.
Since it is directly derived from a GtkItem it can be treated as such by using the GTK_ITEM (TreeItem) macro. A GtkTreeItem usually holds a label, so the convenience function gtk_list_item_new_with_label() is provided. The same effect can be achieved using code like the following, which is actually copied verbatim from gtk_tree_item_new_with_label():
tree_item = gtk_tree_item_new ();
label_widget = gtk_label_new (label);
gtk_misc_set_alignment (GTK_MISC (label_widget), 0.0, 0.5);
gtk_container_add (GTK_CONTAINER (tree_item), label_widget);
gtk_widget_show (label_widget);
As one is not forced to add a GtkLabel to a GtkTreeItem, you could also add a GtkHBox or a GtkArrow, or even a GtkNotebook (though your app will likely be quite unpopular in this case) to the GtkTreeItem.
If you remove all the items from a subtree, it will be destroyed and unparented, unless you reference it beforehand, and the GtkTreeItem which owns it will be collapsed. So, if you want it to stick around, do something like the following:
gtk_widget_ref (tree);
owner = GTK_TREE(tree)->tree_owner;
gtk_container_remove (GTK_CONTAINER(tree), item);
if (tree->parent == NULL){
gtk_tree_item_expand (GTK_TREE_ITEM(owner));
gtk_tree_item_set_subtree (GTK_TREE_ITEM(owner), tree);
}
else
gtk_widget_unref (tree);
Finally, drag-n-drop does work with GtkTreeItems. You just have to make sure that the GtkTreeItem you want to make into a drag item or a drop site has not only been added to a GtkTree, but that each successive parent widget has a parent itself, all the way back to a toplevel or dialog window, when you call gtk_widget_dnd_drag_set() or gtk_widget_dnd_drop_set(). Otherwise, strange things will happen.
GtkTreeItem inherits the "select", "deselect", and "toggle" signals from GtkItem. In addition, it adds two signals of its own, "expand" and "collapse".
void select( GtkItem *tree_item );
This signal is emitted when an item is about to be selected, either after it has been clicked on by the user, or when the program calls gtk_tree_item_select(), gtk_item_select(), or gtk_tree_select_child().
void deselect( GtkItem *tree_item );
This signal is emitted when an item is about to be unselected, either after it has been clicked on by the user, or when the program calls gtk_tree_item_deselect() or gtk_item_deselect(). In the case of GtkTreeItems, it is also emitted by gtk_tree_unselect_child(), and sometimes gtk_tree_select_child().
void toggle( GtkItem *tree_item );
This signal is emitted when the program calls gtk_item_toggle(). The effect it has when emitted on a GtkTreeItem is to call gtk_tree_select_child() (and never gtk_tree_unselect_child()) on the item's parent tree, if the item has a parent tree. If it doesn't, then the highlight is reversed on the item.
void expand( GtkTreeItem *tree_item );
This signal is emitted when the tree item's subtree is about to be expanded, that is, when the user clicks on the plus sign next to the item, or when the program calls gtk_tree_item_expand().
void collapse( GtkTreeItem *tree_item );
This signal is emitted when the tree item's subtree is about to be collapsed, that is, when the user clicks on the minus sign next to the item, or when the program calls gtk_tree_item_collapse().
guint gtk_tree_item_get_type( void );
Returns the `GtkTreeItem' type identifier.
GtkWidget* gtk_tree_item_new( void );
Create a new GtkTreeItem object. The new widget is returned as a pointer to a GtkWidget object. NULL is returned on failure.
GtkWidget* gtk_tree_item_new_with_label (gchar *label);
Create a new GtkTreeItem object, having a single GtkLabel as the sole child. The new widget is returned as a pointer to a GtkWidget object. NULL is returned on failure.
void gtk_tree_item_select( GtkTreeItem *tree_item );
This function is basically a wrapper around a call to gtk_item_select (GTK_ITEM (tree_item)) which will emit the select signal.
void gtk_tree_item_deselect( GtkTreeItem *tree_item );
This function is basically a wrapper around a call to gtk_item_deselect (GTK_ITEM (tree_item)) which will emit the deselect signal.
void gtk_tree_item_set_subtree( GtkTreeItem *tree_item,
GtkWidget *subtree );
This function adds subtree to tree_item, showing it if tree_item is expanded, or hiding it if tree_item is collapsed. Again, remember that the tree_item must have already been added to a tree for this to work.
void gtk_tree_item_remove_subtree( GtkTreeItem *tree_item );
This removes all of tree_item's subtree's children (thus unreferencing and destroying it, any of its children's subtrees, and so on...), then removes the subtree itself, and hides the plus/minus sign.
void gtk_tree_item_expand( GtkTreeItem *tree_item );
This emits the "expand" signal on tree_item, which expands it.
void gtk_tree_item_collapse( GtkTreeItem *tree_item );
This emits the "collapse" signal on tree_item, which collapses it.
GtkTreeItem *GTK_TREE_ITEM (gpointer obj)
Cast a generic pointer to `GtkTreeItem*'.
GtkTreeItemClass *GTK_TREE_ITEM_CLASS (gpointer obj)
Cast a generic pointer to `GtkTreeItemClass'.
gint GTK_IS_TREE_ITEM (gpointer obj)
Determine if a generic pointer refers to a `GtkTreeItem' object.
GtkWidget GTK_TREE_ITEM_SUBTREE (gpointer obj)
Returns a tree item's subtree (obj should point to a `GtkTreeItem' object).
This is somewhat like the tree example in testgtk.c, but a lot less complete (although much better commented). It puts up a window with a tree, and connects all the signals for the relevant objects, so you can see when they are emitted.
/* example-start tree tree.c */
#include <gtk/gtk.h>
/* for all the GtkItem:: and GtkTreeItem:: signals */
static void cb_itemsignal (GtkWidget *item, gchar *signame)
{
gchar *name;
GtkLabel *label;
/* It's a GtkBin, so it has one child, which we know to be a
label, so get that */
label = GTK_LABEL (GTK_BIN (item)->child);
/* Get the text of the label */
gtk_label_get (label, &name);
/* Get the level of the tree which the item is in */
g_print ("%s called for item %s->%p, level %d\n", signame, name,
item, GTK_TREE (item->parent)->level);
}
/* Note that this is never called */
static void cb_unselect_child (GtkWidget *root_tree, GtkWidget *child,
GtkWidget *subtree)
{
g_print ("unselect_child called for root tree %p, subtree %p, child %p\n",
root_tree, subtree, child);
}
/* Note that this is called every time the user clicks on an item,
whether it is already selected or not. */
static void cb_select_child (GtkWidget *root_tree, GtkWidget *child,
GtkWidget *subtree)
{
g_print ("select_child called for root tree %p, subtree %p, child %p\n",
root_tree, subtree, child);
}
static void cb_selection_changed (GtkWidget *tree)
{
GList *i;
g_print ("selection_change called for tree %p\n", tree);
g_print ("selected objects are:\n");
i = GTK_TREE_SELECTION(tree);
while (i){
gchar *name;
GtkLabel *label;
GtkWidget *item;
/* Get a GtkWidget pointer from the list node */
item = GTK_WIDGET (i->data);
label = GTK_LABEL (GTK_BIN (item)->child);
gtk_label_get (label, &name);
g_print ("\t%s on level %d\n", name, GTK_TREE
(item->parent)->level);
i = i->next;
}
}
int main (int argc, char *argv[])
{
GtkWidget *window, *scrolled_win, *tree;
static gchar *itemnames[] = {"Foo", "Bar", "Baz", "Quux",
"Maurice"};
gint i;
gtk_init (&argc, &argv);
/* a generic toplevel window */
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
gtk_signal_connect (GTK_OBJECT(window), "delete_event",
GTK_SIGNAL_FUNC (gtk_main_quit), NULL);
gtk_container_set_border_width (GTK_CONTAINER(window), 5);
/* A generic scrolled window */
scrolled_win = gtk_scrolled_window_new (NULL, NULL);
gtk_scrolled_window_set_policy (GTK_SCROLLED_WINDOW (scrolled_win),
GTK_POLICY_AUTOMATIC,
GTK_POLICY_AUTOMATIC);
gtk_widget_set_usize (scrolled_win, 150, 200);
gtk_container_add (GTK_CONTAINER(window), scrolled_win);
gtk_widget_show (scrolled_win);
/* Create the root tree */
tree = gtk_tree_new();
g_print ("root tree is %p\n", tree);
/* connect all GtkTree:: signals */
gtk_signal_connect (GTK_OBJECT(tree), "select_child",
GTK_SIGNAL_FUNC(cb_select_child), tree);
gtk_signal_connect (GTK_OBJECT(tree), "unselect_child",
GTK_SIGNAL_FUNC(cb_unselect_child), tree);
gtk_signal_connect (GTK_OBJECT(tree), "selection_changed",
GTK_SIGNAL_FUNC(cb_selection_changed), tree);
/* Add it to the scrolled window */
gtk_scrolled_window_add_with_viewport (GTK_SCROLLED_WINDOW(scrolled_win),
tree);
/* Set the selection mode */
gtk_tree_set_selection_mode (GTK_TREE(tree),
GTK_SELECTION_MULTIPLE);
/* Show it */
gtk_widget_show (tree);
for (i = 0; i < 5; i++){
GtkWidget *subtree, *item;
gint j;
/* Create a tree item */
item = gtk_tree_item_new_with_label (itemnames[i]);
/* Connect all GtkItem:: and GtkTreeItem:: signals */
gtk_signal_connect (GTK_OBJECT(item), "select",
GTK_SIGNAL_FUNC(cb_itemsignal), "select");
gtk_signal_connect (GTK_OBJECT(item), "deselect",
GTK_SIGNAL_FUNC(cb_itemsignal), "deselect");
gtk_signal_connect (GTK_OBJECT(item), "toggle",
GTK_SIGNAL_FUNC(cb_itemsignal), "toggle");
gtk_signal_connect (GTK_OBJECT(item), "expand",
GTK_SIGNAL_FUNC(cb_itemsignal), "expand");
gtk_signal_connect (GTK_OBJECT(item), "collapse",
GTK_SIGNAL_FUNC(cb_itemsignal), "collapse");
/* Add it to the parent tree */
gtk_tree_append (GTK_TREE(tree), item);
/* Show it - this can be done at any time */
gtk_widget_show (item);
/* Create this item's subtree */
subtree = gtk_tree_new();
g_print ("-> item %s->%p, subtree %p\n", itemnames[i], item,
subtree);
/* This is still necessary if you want these signals to be called
for the subtree's children. Note that selection_change will be
signalled for the root tree regardless. */
gtk_signal_connect (GTK_OBJECT(subtree), "select_child",
GTK_SIGNAL_FUNC(cb_select_child), subtree);
gtk_signal_connect (GTK_OBJECT(subtree), "unselect_child",
GTK_SIGNAL_FUNC(cb_unselect_child), subtree);
/* This has absolutely no effect, because it is completely ignored
in subtrees */
gtk_tree_set_selection_mode (GTK_TREE(subtree),
GTK_SELECTION_SINGLE);
/* Neither does this, but for a rather different reason - the
view_mode and view_line values of a tree are propagated to
subtrees when they are mapped. So, setting it later on would
actually have a (somewhat unpredictable) effect */
gtk_tree_set_view_mode (GTK_TREE(subtree), GTK_TREE_VIEW_ITEM);
/* Set this item's subtree - note that you cannot do this until
AFTER the item has been added to its parent tree! */
gtk_tree_item_set_subtree (GTK_TREE_ITEM(item), subtree);
for (j = 0; j < 5; j++){
GtkWidget *subitem;
/* Create a subtree item, in much the same way */
subitem = gtk_tree_item_new_with_label (itemnames[j]);
/* Connect all GtkItem:: and GtkTreeItem:: signals */
gtk_signal_connect (GTK_OBJECT(subitem), "select",
GTK_SIGNAL_FUNC(cb_itemsignal), "select");
gtk_signal_connect (GTK_OBJECT(subitem), "deselect",
GTK_SIGNAL_FUNC(cb_itemsignal), "deselect");
gtk_signal_connect (GTK_OBJECT(subitem), "toggle",
GTK_SIGNAL_FUNC(cb_itemsignal), "toggle");
gtk_signal_connect (GTK_OBJECT(subitem), "expand",
GTK_SIGNAL_FUNC(cb_itemsignal), "expand");
gtk_signal_connect (GTK_OBJECT(subitem), "collapse",
GTK_SIGNAL_FUNC(cb_itemsignal), "collapse");
g_print ("-> -> item %s->%p\n", itemnames[j], subitem);
/* Add it to its parent tree */
gtk_tree_append (GTK_TREE(subtree), subitem);
/* Show it */
gtk_widget_show (subitem);
}
}
/* Show the window and loop endlessly */
gtk_widget_show (window);
gtk_main();
return 0;
}
/* example-end */