291 lines
10 KiB
Markdown
291 lines
10 KiB
Markdown
|
Title: Tree and List Widget Overview
|
||
|
|
Slug: gtk-treeview
|
||
|
|
|
||
|
|
This document describes the `GtkTreeView` widget and auxiliary
|
||
|
|
classes, like tree models and cell renderers. All of these have
|
||
|
|
been deprecated and will be removed in GTK 5. Their replacements
|
||
|
|
are described in the [List Widget Overview](section-list-widget.html).
|
||
|
|
|
||
|
|
## Introduction
|
||
|
|
|
||
|
|
To create a tree or list in GTK, use the `GtkTreeModel` interface in
|
||
|
|
conjunction with the `GtkTreeView` widget. This widget is designed around
|
||
|
|
a _Model/View/Controller_ design and consists of four major parts:
|
||
|
|
|
||
|
|
- The tree view widget (GtkTreeView)
|
||
|
|
- The view column (GtkTreeViewColumn)
|
||
|
|
- The cell renderers (GtkCellRenderer etc.)
|
||
|
|
- The model interface (GtkTreeModel)
|
||
|
|
|
||
|
|
The _View_ is composed of the first three objects, while the last is the
|
||
|
|
_Model_. One of the prime benefits of the MVC design is that multiple views
|
||
|
|
can be created of a single model. For example, a model mapping the file
|
||
|
|
system could be created for a file manager. Many views could be created
|
||
|
|
to display various parts of the file system, but only one copy need be
|
||
|
|
kept in memory.
|
||
|
|
|
||
|
|
The purpose of the cell renderers is to provide extensibility to the
|
||
|
|
widget and to allow multiple ways of rendering the same type of data.
|
||
|
|
For example, consider how to render a boolean variable. Should it
|
||
|
|
render it as a string of "True" or "False", "On" or "Off", or should
|
||
|
|
it be rendered as a checkbox?
|
||
|
|
|
||
|
|
## Creating a model
|
||
|
|
|
||
|
|
GTK provides two simple models that can be used: the `GtkListStore`
|
||
|
|
and the `GtkTreeStore`. `GtkListStore` is used to model list widgets,
|
||
|
|
while the `GtkTreeStore` models trees. It is possible to develop a new
|
||
|
|
type of model, but the existing models should be satisfactory for all
|
||
|
|
but the most specialized of situations. Creating the model is quite
|
||
|
|
|
||
|
|
``` {.c}
|
||
|
|
GtkListStore *store = gtk_list_store_new (2, G_TYPE_STRING, G_TYPE_BOOLEAN);
|
||
|
|
```
|
||
|
|
|
||
|
|
This creates a list store with two columns: a string column and a boolean
|
||
|
|
column. Typically the 2 is never passed directly like that; usually an
|
||
|
|
enum is created wherein the different columns are enumerated, followed by
|
||
|
|
a token that represents the total number of columns. The next example will
|
||
|
|
illustrate this, only using a tree store instead of a list store. Creating
|
||
|
|
a tree store operates almost exactly the same.
|
||
|
|
|
||
|
|
``` {.c}
|
||
|
|
enum
|
||
|
|
{
|
||
|
|
TITLE_COLUMN,
|
||
|
|
AUTHOR_COLUMN,
|
||
|
|
CHECKED_COLUMN,
|
||
|
|
N_COLUMNS
|
||
|
|
};
|
||
|
|
|
||
|
|
GtkTreeStore *store = gtk_tree_store_new (N_COLUMNS, /* Total number of columns */
|
||
|
|
G_TYPE_STRING, /* Book title */
|
||
|
|
G_TYPE_STRING, /* Author */
|
||
|
|
G_TYPE_BOOLEAN); /* Is checked out? */
|
||
|
|
```
|
||
|
|
|
||
|
|
Adding data to the model is done using gtk_tree_store_set() or
|
||
|
|
gtk_list_store_set(), depending upon which sort of model was
|
||
|
|
created. To do this, a `GtkTreeIter` must be acquired. The iterator
|
||
|
|
points to the location where data will be added.
|
||
|
|
|
||
|
|
Once an iterator has been acquired, gtk_tree_store_set() is used to
|
||
|
|
apply data to the part of the model that the iterator points to.
|
||
|
|
Consider the following example:
|
||
|
|
|
||
|
|
``` {.c}
|
||
|
|
GtkTreeIter iter;
|
||
|
|
|
||
|
|
gtk_tree_store_append (store, &iter, NULL); /* Acquire an iterator */
|
||
|
|
|
||
|
|
gtk_tree_store_set (store, &iter,
|
||
|
|
TITLE_COLUMN, "The Principle of Reason",
|
||
|
|
AUTHOR_COLUMN, "Martin Heidegger",
|
||
|
|
CHECKED_COLUMN, FALSE,
|
||
|
|
-1);
|
||
|
|
```
|
||
|
|
|
||
|
|
Notice that the last argument is -1. This is always done because
|
||
|
|
this is a variable-argument function and it needs to know when to stop
|
||
|
|
processing arguments. It can be used to set the data in any or all
|
||
|
|
columns in a given row.
|
||
|
|
|
||
|
|
The third argument to gtk_tree_store_append() is the parent iterator.
|
||
|
|
It is used to add a row to a GtkTreeStore as a child of an existing row.
|
||
|
|
This means that the new row will only be visible when its parent is visible
|
||
|
|
and in its expanded state. Consider the following example:
|
||
|
|
|
||
|
|
``` {.c}
|
||
|
|
GtkTreeIter iter1; /* Parent iter */
|
||
|
|
GtkTreeIter iter2; /* Child iter */
|
||
|
|
|
||
|
|
gtk_tree_store_append (store, &iter1, NULL); /* Acquire a top-level iterator */
|
||
|
|
gtk_tree_store_set (store, &iter1,
|
||
|
|
TITLE_COLUMN, "The Art of Computer Programming",
|
||
|
|
AUTHOR_COLUMN, "Donald E. Knuth",
|
||
|
|
CHECKED_COLUMN, FALSE,
|
||
|
|
-1);
|
||
|
|
|
||
|
|
gtk_tree_store_append (store, &iter2, &iter1); /* Acquire a child iterator */
|
||
|
|
gtk_tree_store_set (store, &iter2,
|
||
|
|
TITLE_COLUMN, "Volume 1: Fundamental Algorithms",
|
||
|
|
-1);
|
||
|
|
|
||
|
|
gtk_tree_store_append (store, &iter2, &iter1);
|
||
|
|
gtk_tree_store_set (store, &iter2,
|
||
|
|
TITLE_COLUMN, "Volume 2: Seminumerical Algorithms",
|
||
|
|
-1);
|
||
|
|
|
||
|
|
gtk_tree_store_append (store, &iter2, &iter1);
|
||
|
|
gtk_tree_store_set (store, &iter2,
|
||
|
|
TITLE_COLUMN, "Volume 3: Sorting and Searching",
|
||
|
|
-1);
|
||
|
|
```
|
||
|
|
|
||
|
|
## Creating the view component
|
||
|
|
|
||
|
|
While there are several different models to choose from, there is
|
||
|
|
only one view widget to deal with. It works with either the list
|
||
|
|
or the tree store. Setting up a `GtkTreeView` is not a difficult
|
||
|
|
matter. It needs a `GtkTreeModel` to know where to retrieve its data
|
||
|
|
from.
|
||
|
|
|
||
|
|
``` {.c}
|
||
|
|
GtkWidget *tree;
|
||
|
|
|
||
|
|
tree = gtk_tree_view_new_with_model (GTK_TREE_MODEL (store));
|
||
|
|
```
|
||
|
|
|
||
|
|
## Columns and cell renderers
|
||
|
|
|
||
|
|
Once the `GtkTreeView` widget has a model, it will need to know how
|
||
|
|
to display the model. It does this with columns and cell renderers.
|
||
|
|
|
||
|
|
Cell renderers are used to draw the data in the tree model in a
|
||
|
|
way. There are a number of cell renderers that come with GTK,
|
||
|
|
including the `GtkCellRendererText`, `GtkCellRendererPixbuf` and
|
||
|
|
the `GtkCellRendererToggle`. It is relatively easy to write a
|
||
|
|
custom renderer.
|
||
|
|
|
||
|
|
A `GtkTreeViewColumn` is the object that `GtkTreeView` uses to organize
|
||
|
|
the vertical columns in the tree view. It needs to know the name of
|
||
|
|
the column to label for the user, what type of cell renderer to use,
|
||
|
|
and which piece of data to retrieve from the model for a given row.
|
||
|
|
|
||
|
|
``` {.c}
|
||
|
|
GtkCellRenderer *renderer;
|
||
|
|
GtkTreeViewColumn *column;
|
||
|
|
|
||
|
|
renderer = gtk_cell_renderer_text_new (<!-- -->);
|
||
|
|
column = gtk_tree_view_column_new_with_attributes ("Author",
|
||
|
|
renderer,
|
||
|
|
"text", AUTHOR_COLUMN,
|
||
|
|
NULL);
|
||
|
|
gtk_tree_view_append_column (GTK_TREE_VIEW (tree), column);
|
||
|
|
```
|
||
|
|
|
||
|
|
At this point, all the steps in creating a displayable tree have been
|
||
|
|
covered. The model is created, data is stored in it, a tree view is
|
||
|
|
created and columns are added to it.
|
||
|
|
|
||
|
|
## Selection handling
|
||
|
|
|
||
|
|
Most applications will need to not only deal with displaying data,
|
||
|
|
but also receiving input events from users. To do this, simply get
|
||
|
|
a reference to a selection object and connect to the
|
||
|
|
`GtkTreeSelection::changed` signal.
|
||
|
|
|
||
|
|
``` {.c}
|
||
|
|
/* Prototype for selection handler callback */
|
||
|
|
static void tree_selection_changed_cb (GtkTreeSelection *selection, gpointer data);
|
||
|
|
|
||
|
|
/* Setup the selection handler */
|
||
|
|
GtkTreeSelection *select;
|
||
|
|
|
||
|
|
select = gtk_tree_view_get_selection (GTK_TREE_VIEW (tree));
|
||
|
|
gtk_tree_selection_set_mode (select, GTK_SELECTION_SINGLE);
|
||
|
|
g_signal_connect (G_OBJECT (select), "changed",
|
||
|
|
G_CALLBACK (tree_selection_changed_cb),
|
||
|
|
NULL);
|
||
|
|
```
|
||
|
|
|
||
|
|
Then to retrieve data for the row selected:
|
||
|
|
|
||
|
|
``` {.c}
|
||
|
|
static void
|
||
|
|
tree_selection_changed_cb (GtkTreeSelection *selection, gpointer data)
|
||
|
|
{
|
||
|
|
GtkTreeIter iter;
|
||
|
|
GtkTreeModel *model;
|
||
|
|
char *author;
|
||
|
|
|
||
|
|
if (gtk_tree_selection_get_selected (selection, &model, &iter))
|
||
|
|
{
|
||
|
|
gtk_tree_model_get (model, &iter, AUTHOR_COLUMN, &author, -1);
|
||
|
|
|
||
|
|
g_print ("You selected a book by %s\n", author);
|
||
|
|
|
||
|
|
g_free (author);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
```
|
||
|
|
|
||
|
|
## Simple Example
|
||
|
|
|
||
|
|
Here is a simple example of using a `GtkTreeView` widget in context
|
||
|
|
of the other widgets. It simply creates a simple model and view,
|
||
|
|
and puts them together. Note that the model is never populated
|
||
|
|
with data — that is left as an exercise for the reader.
|
||
|
|
More information can be found on this in the `GtkTreeModel` section.
|
||
|
|
|
||
|
|
``` {.c}
|
||
|
|
enum
|
||
|
|
{
|
||
|
|
TITLE_COLUMN,
|
||
|
|
AUTHOR_COLUMN,
|
||
|
|
CHECKED_COLUMN,
|
||
|
|
N_COLUMNS
|
||
|
|
};
|
||
|
|
|
||
|
|
void
|
||
|
|
setup_tree (void)
|
||
|
|
{
|
||
|
|
GtkTreeStore *store;
|
||
|
|
GtkWidget *tree;
|
||
|
|
GtkTreeViewColumn *column;
|
||
|
|
GtkCellRenderer *renderer;
|
||
|
|
|
||
|
|
/* Create a model. We are using the store model for now, though we
|
||
|
|
* could use any other GtkTreeModel */
|
||
|
|
store = gtk_tree_store_new (N_COLUMNS,
|
||
|
|
G_TYPE_STRING,
|
||
|
|
G_TYPE_STRING,
|
||
|
|
G_TYPE_BOOLEAN);
|
||
|
|
|
||
|
|
/* custom function to fill the model with data */
|
||
|
|
populate_tree_model (store);
|
||
|
|
|
||
|
|
/* Create a view */
|
||
|
|
tree = gtk_tree_view_new_with_model (GTK_TREE_MODEL (store));
|
||
|
|
|
||
|
|
/* The view now holds a reference. We can get rid of our own
|
||
|
|
* reference */
|
||
|
|
g_object_unref (G_OBJECT (store));
|
||
|
|
|
||
|
|
/* Create a cell render and arbitrarily make it red for demonstration
|
||
|
|
* purposes */
|
||
|
|
renderer = gtk_cell_renderer_text_new (<!-- -->);
|
||
|
|
g_object_set (G_OBJECT (renderer),
|
||
|
|
"foreground", "red",
|
||
|
|
NULL);
|
||
|
|
|
||
|
|
/* Create a column, associating the "text" attribute of the
|
||
|
|
* cell_renderer to the first column of the model */
|
||
|
|
column = gtk_tree_view_column_new_with_attributes ("Author", renderer,
|
||
|
|
"text", AUTHOR_COLUMN,
|
||
|
|
NULL);
|
||
|
|
|
||
|
|
/* Add the column to the view. */
|
||
|
|
gtk_tree_view_append_column (GTK_TREE_VIEW (tree), column);
|
||
|
|
|
||
|
|
/* Second column.. title of the book. */
|
||
|
|
renderer = gtk_cell_renderer_text_new (<!-- -->);
|
||
|
|
column = gtk_tree_view_column_new_with_attributes ("Title",
|
||
|
|
renderer,
|
||
|
|
"text", TITLE_COLUMN,
|
||
|
|
NULL);
|
||
|
|
gtk_tree_view_append_column (GTK_TREE_VIEW (tree), column);
|
||
|
|
|
||
|
|
/* Last column.. whether a book is checked out. */
|
||
|
|
renderer = gtk_cell_renderer_toggle_new (<!-- -->);
|
||
|
|
column = gtk_tree_view_column_new_with_attributes ("Checked out",
|
||
|
|
renderer,
|
||
|
|
"active", CHECKED_COLUMN,
|
||
|
|
NULL);
|
||
|
|
gtk_tree_view_append_column (GTK_TREE_VIEW (tree), column);
|
||
|
|
|
||
|
|
/* Now we can manipulate the view just like any other GTK widget */
|
||
|
|
...
|
||
|
|
}
|
||
|
|
```
|