Description
The GtkTreeModel interface defines a generic tree interface for use by
the GtkTreeView widget. It is an abstract interface, and is designed
to be usable with any appropriate data structure. The programmer just
has to implement this interface on their own data type for it to be
viewable by a GtkTreeView widget.
The model is represented as a hierarchical tree of strongly-typed,
columned data. In other words, the model can be seen as a tree where
every node has different values depending on which column is being
queried. The type of data found in a column is determined by using the
GType system (ie. G_TYPE_INT, GTK_TYPE_BUTTON, G_TYPE_POINTER, etc.).
The types are homogeneous per column across all nodes. It is important
to note that this interface only provides a way of examining a model and
observing changes. The implementation of each individual model decides
how and if changes are made.
In order to make life simpler for programmers who do not need to write
their own specialized model, two generic models are provided — the
GtkTreeStore and the GtkListStore. To use these, the developer simply
pushes data into these models as necessary. These models provide the
data structure as well as all appropriate tree interfaces. As a result,
implementing drag and drop, sorting, and storing data is trivial. For
the vast majority of trees and lists, these two models are sufficient.
Models are accessed on a node/column level of granularity. One can
query for the value of a model at a certain node and a certain column
on that node. There are two structures used to reference a particular
node in a model. They are the GtkTreePath and the GtkTreeIter
[1]
Most of the interface consists of operations on a GtkTreeIter.
A path is essentially a potential node. It is a location on a model
that may or may not actually correspond to a node on a specific model.
The GtkTreePath struct can be converted into either an array of
unsigned integers or a string. The string form is a list of numbers
separated by a colon. Each number refers to the offset at that level.
Thus, the path "0" refers to the root node and the path
"2:4" refers to the fifth child of the third node.
By contrast, a GtkTreeIter is a reference to a specific node on a
specific model. It is a generic struct with an integer and three
generic pointers. These are filled in by the model in a model-specific
way. One can convert a path to an iterator by calling
gtk_tree_model_get_iter(). These iterators are the primary way of
accessing a model and are similar to the iterators used by
GtkTextBuffer. They are generally statically allocated on the heap and
only used for a short time. The model interface defines a set of
operations using them for navigating the model.
It is expected that models fill in the iterator with private data. For
example, the GtkListStore model, which is internally a simple linked
list, stores a list node in one of the pointers. The GtkTreeModelSort
stores an array and an offset in two of the pointers. Additionally,
there is an integer field. This field is generally filled with a unique
stamp per model. This stamp is for catching errors resulting from using
invalid iterators with a model.
The lifecycle of an iterator can be a little confusing at first.
Iterators are expected to always be valid for as long as the model is
unchanged (and doesn't emit a signal). The model is considered to own
all outstanding iterators and nothing needs to be done to free them from
the user's point of view. Additionally, some models guarantee that an
iterator is valid for as long as the node it refers to is valid (most
notably the GtkTreeStore and GtkListStore). Although generally
uninteresting, as one always has to allow for the case where iterators
do not persist beyond a signal, some very important performance
enhancements were made in the sort model. As a result, the
GTK_TREE_MODEL_ITERS_PERSIST flag was added to indicate this behavior.
To help show some common operation of a model, some examples are
provided. The first example shows three ways of getting the iter at the
location "3:2:5". While the first method shown is easier,
the second is much more common, as you often get paths from callbacks.
Example 1. Acquiring a GtkTreeIter
/* Three ways of getting the iter pointing to the location
*/
{
GtkTreePath *path;
GtkTreeIter iter;
GtkTreeIter parent_iter;
/* get the iterator from a string */
gtk_tree_model_get_iter_from_string (model, &iter, "3:2:5");
/* get the iterator from a path */
path = gtk_tree_path_new_from_string ("3:2:5");
gtk_tree_model_get_iter (model, &iter, path);
gtk_tree_path_free (path);
/* walk the tree to find the iterator */
gtk_tree_model_get_nth_child (model, &iter, NULL, 3);
parent_iter = iter;
gtk_tree_model_get_nth_child (model, &iter, &parent_iter, 2);
parent_iter = iter;
gtk_tree_model_get_nth_child (model, &iter, NULL, 5);
} |
This second example shows a quick way of iterating through a list and
getting a string and an integer from each row. The
populate_model function used below is not shown, as
it is specific to the GtkListStore. For information on how to write
such a function, see the GtkListStore documentation.
Example 2. Reading data from a GtkTreeModel
enum
{
STRING_COLUMN,
INT_COLUMN,
N_COLUMNS
};
{
GtkTreeModel *list_store;
GtkTreeIter iter;
gboolean valid;
gint row_count = 0;
/* make a new list_store */
list_store = gtk_list_store_new (N_COLUMNS, G_TYPE_STRING, G_TYPE_INT);
/* Fill the list store with data */
populate_model (list_store);
/* Get the first iter in the list */
valid = gtk_tree_model_get_iter_first (model, &iter);
while (valid)
{
/* Walk through the list, reading each row */
gchar *str_data;
gint int_data;
/* Make sure you terminate calls to gtk_tree_model_get()
* with a '-1' value
*/
gtk_tree_model_get (list_store, &iter,
STRING_COLUMN, &str_data,
INT_COLUMN, &int_data,
-1);
/* Do something with the data */
g_print ("Row %d: (%s,%d)\n", row_count, str_data, int_data);
g_free (str_data);
row_count ++;
valid = gtk_tree_model_iter_next (model, &iter))
}
} |
Details
struct GtkTreeIter
struct GtkTreeIter
{
gint stamp;
gpointer user_data;
gpointer user_data2;
gpointer user_data3;
}; |
The GtkTreeIter is the primary structure for
accessing a structure. Models are expected to put a unique integer in
the stamp member, and put model-specific
data in the three user_data members.
struct GtkTreeRowReference
struct GtkTreeRowReference; |
struct GtkTreeModelIface
struct GtkTreeModelIface
{
GTypeInterface g_iface;
/* Signals */
void (* row_changed) (GtkTreeModel *tree_model,
GtkTreePath *path,
GtkTreeIter *iter);
void (* row_inserted) (GtkTreeModel *tree_model,
GtkTreePath *path,
GtkTreeIter *iter);
void (* row_has_child_toggled) (GtkTreeModel *tree_model,
GtkTreePath *path,
GtkTreeIter *iter);
void (* row_deleted) (GtkTreeModel *tree_model,
GtkTreePath *path);
void (* rows_reordered) (GtkTreeModel *tree_model,
GtkTreePath *path,
GtkTreeIter *iter,
gint *new_order);
/* Virtual Table */
GtkTreeModelFlags (* get_flags) (GtkTreeModel *tree_model);
gint (* get_n_columns) (GtkTreeModel *tree_model);
GType (* get_column_type) (GtkTreeModel *tree_model,
gint index);
gboolean (* get_iter) (GtkTreeModel *tree_model,
GtkTreeIter *iter,
GtkTreePath *path);
GtkTreePath *(* get_path) (GtkTreeModel *tree_model,
GtkTreeIter *iter);
void (* get_value) (GtkTreeModel *tree_model,
GtkTreeIter *iter,
gint column,
GValue *value);
gboolean (* iter_next) (GtkTreeModel *tree_model,
GtkTreeIter *iter);
gboolean (* iter_children) (GtkTreeModel *tree_model,
GtkTreeIter *iter,
GtkTreeIter *parent);
gboolean (* iter_has_child) (GtkTreeModel *tree_model,
GtkTreeIter *iter);
gint (* iter_n_children) (GtkTreeModel *tree_model,
GtkTreeIter *iter);
gboolean (* iter_nth_child) (GtkTreeModel *tree_model,
GtkTreeIter *iter,
GtkTreeIter *parent,
gint n);
gboolean (* iter_parent) (GtkTreeModel *tree_model,
GtkTreeIter *iter,
GtkTreeIter *child);
void (* ref_node) (GtkTreeModel *tree_model,
GtkTreeIter *iter);
void (* unref_node) (GtkTreeModel *tree_model,
GtkTreeIter *iter);
}; |
GtkTreeModelForeachFunc ()
enum GtkTreeModelFlags
typedef enum
{
GTK_TREE_MODEL_ITERS_PERSIST = 1 << 0,
GTK_TREE_MODEL_LIST_ONLY = 1 << 1
} GtkTreeModelFlags; |
These flags indicate various properties of a GtkTreeModel. They are
returned by gtk_tree_model_get_flags(), and must be static for the
lifetime of the object. A more complete description of
GTK_TREE_MODEL_ITERS_PERSIST can be found in the overview of this
section.
gtk_tree_path_new ()
Creates a new GtkTreePath. This structure refers to a row.
gtk_tree_path_new_from_string ()
GtkTreePath* gtk_tree_path_new_from_string (const gchar *path); |
Creates a new GtkTreePath initialized to path. path is expected to be a
colon separated list of numbers. For example, the string "10:4:0" would
create a path of depth 3 pointing to the 11th child of the root node, the 5th
child of that 11th child, and the 1st child of that 5th child. If an invalid
path string is passed in, NULL is returned.
gtk_tree_path_to_string ()
Generates a string representation of the path. This string is a ':'
separated list of numbers. For example, "4:10:0:3" would be an acceptable return value for this string.
gtk_tree_path_new_first ()
Creates a new GtkTreePath. The string representation of this path is "0"
gtk_tree_path_new_root()
#define gtk_tree_path_new_root() gtk_tree_path_new_first() |
A alternate name for gtk_tree_path_new_root() provided for
compatibility reasons; this macro will be deprecated in future
versions of GTK+.
gtk_tree_path_append_index ()
void gtk_tree_path_append_index (GtkTreePath *path,
gint index); |
Appends a new index to a path. As a result, the depth of the path is
increased.
gtk_tree_path_prepend_index ()
void gtk_tree_path_prepend_index (GtkTreePath *path,
gint index); |
Prepends a new index to a path. As a result, the depth of the path is
increased.
gtk_tree_path_get_depth ()
Returns the current depth of path.
gtk_tree_path_get_indices ()
Returns the current indices of path. This is an array of integers, each
representing a node in a tree. This value should not be freed.
gtk_tree_path_free ()
Frees path.
gtk_tree_path_copy ()
Creates a new GtkTreePath as a copy of path.
gtk_tree_path_compare ()
Compares two paths. If a appears before b in a tree, then -1 is returned.
If b appears before a, then 1 is returned. If the two nodes are equal,
then 0 is returned.
gtk_tree_path_next ()
Moves the path to point to the next node at the current depth.
gtk_tree_path_prev ()
Moves the path to point to the previous node at the current depth, if it exists.
gtk_tree_path_up ()
Moves the path to point to it's parent node, if it has a parent.
gtk_tree_path_down ()
Moves path to point to the first child of the current path.
gtk_tree_path_is_ancestor ()
Returns TRUE if descendant is a descendant of path.
gtk_tree_path_is_descendant ()
Returns TRUE if path is a descendant of ancestor.
gtk_tree_row_reference_new ()
Creates a row reference based on path. This reference will keep pointing to
the node pointed to by path, so long as it exists. It listens to all
signals emitted by model, and updates it's path appropriately. If path
isn't a valid path in model, then NULL is returned.
gtk_tree_row_reference_new_proxy ()
You do not need to use this function. Creates a row reference based on
path. This reference will keep pointing to the node pointed to by path, so
long as it exists. If path isn't a valid path in model, then NULL is
returned. However, unlike references created with
gtk_tree_row_reference_new(), it does not listen to the model for changes.
The creator of the row reference must do this explicitly using
gtk_tree_row_reference_inserted(), gtk_tree_row_reference_deleted(),
gtk_tree_row_reference_reordered(). This must be called once per signal per
proxy.
This type of row reference is primarily meant by structures that need to
carefully monitor exactly when a row_reference updates itself, and is not
generally needed by most applications.
gtk_tree_row_reference_get_path ()
Returns a path that the row reference currently points to, or NULL if the
path pointed to is no longer valid.
gtk_tree_row_reference_valid ()
Returns TRUE if the reference is non-NULL and refers to a current valid
path.
gtk_tree_row_reference_free ()
Free's reference. reference may be NULL.
gtk_tree_row_reference_inserted ()
void gtk_tree_row_reference_inserted (GObject *proxy,
GtkTreePath *path); |
Lets a set of row reference created by gtk_tree_row_reference_new_proxy()
know that the model emitted the "row_inserted" signal.
gtk_tree_row_reference_deleted ()
void gtk_tree_row_reference_deleted (GObject *proxy,
GtkTreePath *path); |
Lets a set of row reference created by gtk_tree_row_reference_new_proxy()
know that the model emitted the "row_deleted" signal.
gtk_tree_row_reference_reordered ()
void gtk_tree_row_reference_reordered
(GObject *proxy,
GtkTreePath *path,
GtkTreeIter *iter,
gint *new_order); |
Lets a set of row reference created by gtk_tree_row_reference_new_proxy()
know that the model emitted the "rows_reordered" signal.
gtk_tree_iter_copy ()
Creates a dynamically allocated tree iterator as a copy of iter. This
function is not intended for use in applications, because you can just copy
the structs by value (GtkTreeIter new_iter = iter;). You
must free this iter with gtk_tree_iter_free().
gtk_tree_iter_free ()
Frees an iterator that has been allocated on the heap. This function is
mainly used for language bindings.
gtk_tree_model_get_flags ()
Returns a set of flags supported by this interface. The flags are a bitwise
combination of GtkTreeModelFlags. The flags supported should not change
during the lifecycle of the tree_model.
gtk_tree_model_get_n_columns ()
gint gtk_tree_model_get_n_columns (GtkTreeModel *tree_model); |
Returns the number of columns supported by tree_model.
gtk_tree_model_get_column_type ()
GType gtk_tree_model_get_column_type (GtkTreeModel *tree_model,
gint index); |
Returns the type of the column.
gtk_tree_model_get_iter ()
Sets iter to a valid iterator pointing to path.
gtk_tree_model_get_iter_from_string ()
gboolean gtk_tree_model_get_iter_from_string
(GtkTreeModel *tree_model,
GtkTreeIter *iter,
const gchar *path_string); |
Sets iter to a valid iterator pointing to path_string, if it
exists. Otherwise, iter is left invalid and FALSE is returned.
gtk_tree_model_get_iter_first ()
Initializes iter with the first iterator in the tree (the one at the path
"0") and returns TRUE. Returns FALSE if the tree is empty.
gtk_tree_model_get_iter_root()
#define gtk_tree_model_get_iter_root(tree_model, iter) gtk_tree_model_get_iter_first(tree_model, iter) |
A alternate name for gtk_tree_model_get_iter_root() provided for
compatibility reasons; this macro will be deprecated in future
versions of GTK+.
gtk_tree_model_get_value ()
Sets initializes and sets value to that at column. When done with value,
g_value_unset() needs to be called to free any allocated memory.
gtk_tree_model_iter_next ()
Sets iter to point to the node following it at the current level. If there
is no next iter, FALSE is returned and iter is set to be invalid.
gtk_tree_model_iter_children ()
Sets iter to point to the first child of parent. If parent has no children,
FALSE is returned and iter is set to be invalid. parent will remain a valid
node after this function has been called.
gtk_tree_model_iter_has_child ()
Returns TRUE if iter has children, FALSE otherwise.
gtk_tree_model_iter_n_children ()
Returns the number of children that iter has. As a special case, if iter
is NULL, then the number of toplevel nodes is returned.
gtk_tree_model_iter_nth_child ()
Sets iter to be the child of parent, using the given index. The first
index is 0. If index is too big, or parent has no children, iter is set
to an invalid iterator and FALSE is returned. parent will remain a valid
node after this function has been called. As a special case, if parent is
NULL, then the nth root node is set.
gtk_tree_model_iter_parent ()
Sets iter to be the parent of child. If child is at the toplevel, and
doesn't have a parent, then iter is set to an invalid iterator and FALSE
is returned. child will remain a valid node after this function has been
called.
gtk_tree_model_ref_node ()
Lets the tree ref the node. This is an optional method for models to
implement. To be more specific, models may ignore this call as it exists
primarily for performance reasons.
This function is primarily meant as a way for views to let caching model know
when nodes are being displayed (and hence, whether or not to cache that
node.) For example, a file-system based model would not want to keep the
entire file-hierarchy in memory, just the sections that are currently being
displayed by every current view.
A model should be expected to be able to get an iter independent of it's
reffed state.
gtk_tree_model_unref_node ()
Lets the tree unref the node. This is an optional method for models to
implement. To be more specific, models may ignore this call as it exists
primarily for performance reasons.
For more information on what this means, see gtk_tree_model_ref_node().
Please note that nodes that are deleted are not unreffed.
gtk_tree_model_get ()
Gets the value of one or more cells in the row referenced by iter.
The variable argument list should contain integer column numbers,
each column number followed by a place to store the value being
retrieved. The list is terminated by a -1. For example, to get a
value from column 0 with type G_TYPE_STRING, you would
write: gtk_tree_model_get (model, iter, 0, &place_string_here, -1),
where place_string_here is a gchar* to be
filled with the string.
If appropriate, the returned values have to be freed or unreferenced.
gtk_tree_model_get_valist ()
See gtk_tree_model_get(), this version takes a va_list
for language bindings to use.
gtk_tree_model_foreach ()
Calls func on each node in model in a depth-first fashion. If func returns
TRUE, then the tree ceases to be walked, and gtk_tree_model_foreach() returns.
gtk_tree_model_row_changed ()
Emits the "row_changed" signal on tree_model.
gtk_tree_model_row_inserted ()
Emits the "row_inserted" signal on tree_model
gtk_tree_model_row_has_child_toggled ()
Emits the "row_has_child_toggled" signal on tree_model. This should be
called by models after the child state of a node changes.
gtk_tree_model_row_deleted ()
Emits the "row_deleted" signal on tree_model. This should be called by
models after a row has been removed. The location pointed to by path should
be the location that the row previously was at. It may not be a valid
location anymore.
gtk_tree_model_rows_reordered ()
Emits the "rows_reordered" signal on tree_model. This should be called by
models when their rows have been reordered.