Permalink
Switch branches/tags
Nothing to show
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
322 lines (236 sloc) 11.9 KB
Tree and List Widgets
=====================
A :class:`Gtk.TreeView` and its associated widgets are an extremely powerful way
of displaying data. They are used in conjunction with a :class:`Gtk.ListStore`
or :class:`Gtk.TreeStore` and provide a way of displaying and manipulating data
in many ways, including:
* Automatic updates when data is added, removed or edited
* Drag and drop support
* Sorting data
* Embedding widgets such as check boxes, progress bars, etc.
* Reorderable and resizable columns
* Filtering data
With the power and flexibility of a :class:`Gtk.TreeView` comes complexity. It
is often difficult for beginner developers to be able to utilize it correctly due
to the number of methods which are required.
The Model
---------
Each :class:`Gtk.TreeView` has an associated :class:`Gtk.TreeModel`, which
contains the data displayed by the TreeView. Each :class:`Gtk.TreeModel` can be
used by more than one :class:`Gtk.TreeView`. For instance, this allows the same
underlying data to be displayed and edited in 2 different ways at the same time.
Or the 2 Views might display different columns from the same Model data, in the
same way that 2 SQL queries (or "views") might show different fields from the
same database table.
Although you can theoretically implement your own Model, you will normally use
either the :class:`Gtk.ListStore` or :class:`Gtk.TreeStore` model classes.
:class:`Gtk.ListStore` contains simple rows of data, and each row has no children,
whereas :class:`Gtk.TreeStore` contains rows of data, and each row may have child
rows.
When constructing a model you have to specify the data types for each column the
model holds.
.. code-block:: python
store = Gtk.ListStore(str, str, float)
This creates a list store with three columns, two string columns, and a float
column.
Adding data to the model is done using :meth:`Gtk.ListStore.append` or
:meth:`Gtk.TreeStore.append`, depending upon which sort of model was created.
.. code-block:: python
treeiter = store.append(["The Art of Computer Programming",
"Donald E. Knuth", 25.46])
Both methods return a :class:`Gtk.TreeIter` instance, which points to the location
of the newly inserted row. You can retrieve a :class:`Gtk.TreeIter` by calling
:meth:`Gtk.TreeModel.get_iter`.
Once data has been inserted, you can retrieve or modify data using the tree iter
and column index.
.. code-block:: python
print(store[treeiter][2]) # Prints value of third column
store[treeiter][2] = 42.15
As with Python's built-in :class:`list` object you can use :func:`len` to get the number
of rows and use slices to retrieve or set values.
.. code-block:: python
# Print number of rows
print(len(store))
# Print all but first column
print(store[treeiter][1:])
# Print last column
print(store[treeiter][-1])
# Set last two columns
store[treeiter][1:] = ["Donald Ervin Knuth", 41.99]
Iterating over all rows of a tree model is very simple as well.
.. code-block:: python
for row in store:
# Print values of all columns
print(row[:])
Keep in mind, that if you use :class:`Gtk.TreeStore`, the above code will only
iterate over the rows of the top level, but not the children of the nodes.
To iterate over all rows and its children, use the ``print_tree_store`` function.
.. code-block:: python
def print_tree_store(store):
rootiter = store.get_iter_first()
print_rows(store, rootiter, "")
def print_rows(store, treeiter, indent):
while treeiter is not None:
print(indent + str(store[treeiter][:]))
if store.iter_has_child(treeiter):
childiter = store.iter_children(treeiter)
print_rows(store, childiter, indent + "\t")
treeiter = store.iter_next(treeiter)
Apart from accessing values stored in a :class:`Gtk.TreeModel` with the list-like
method mentioned above, it is also possible to
either use :class:`Gtk.TreeIter` or :class:`Gtk.TreePath` instances. Both reference
a particular row in a tree model.
One can convert a path to an iterator by calling :meth:`Gtk.TreeModel.get_iter`.
As :class:`Gtk.ListStore` contains only one level,
i.e. nodes do not have any child nodes, a path is essentially the index of the row
you want to access.
.. code-block:: python
# Get path pointing to 6th row in list store
path = Gtk.TreePath(5)
treeiter = liststore.get_iter(path)
# Get value at 2nd column
value = liststore.get_value(treeiter, 1)
In the case of :class:`Gtk.TreeStore`, a path is a list of indexes 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.
.. code-block:: python
# Get path pointing to 5th child of 3rd row in tree store
path = Gtk.TreePath([2, 4])
treeiter = treestore.get_iter(path)
# Get value at 2nd column
value = treestore.get_value(treeiter, 1)
Instances of :class:`Gtk.TreePath` can be accessed like lists, i.e.
``len(treepath)`` returns the depth of the item ``treepath`` is pointing to,
and ``treepath[i]`` returns the child's index on the *i*-th level.
The View
--------
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 :class:`Gtk.TreeView` is not a difficult matter. It needs a
:class:`Gtk.TreeModel` to know where to retrieve its data from, either by
passing it to the :class:`Gtk.TreeView` constructor, or by calling
:meth:`Gtk.TreeView.set_model`.
.. code-block:: python
tree = Gtk.TreeView(store)
Once the :class:`Gtk.TreeView` 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+, for instance
:class:`Gtk.CellRendererText`, :class:`Gtk.CellRendererPixbuf` and
:class:`Gtk.CellRendererToggle`.
In addition, it is relatively easy to write a custom renderer yourself.
A :class:`Gtk.TreeViewColumn` is the object that :class:`Gtk.TreeView` 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.
.. code-block:: python
renderer = Gtk.CellRendererText()
column = Gtk.TreeViewColumn("Title", renderer, text=0)
tree.append_column(column)
To render more than one model column in a view column, you need to create a
:class:`Gtk.TreeViewColumn` instance and use :meth:`Gtk.TreeViewColumn.pack_start`
to add the model columns to it.
.. code-block:: python
column = Gtk.TreeViewColumn("Title and Author")
title = Gtk.CellRendererText()
author = Gtk.CellRendererText()
column.pack_start(title, True)
column.pack_start(author, True)
column.add_attribute(title, "text", 0)
column.add_attribute(author, "text", 1)
tree.append_column(column)
The Selection
-------------
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 "changed" signal.
.. code-block:: python
select = tree.get_selection()
select.connect("changed", on_tree_selection_changed)
Then to retrieve data for the row selected:
.. code-block:: python
def on_tree_selection_changed(selection):
model, treeiter = selection.get_selected()
if treeiter is not None:
print("You selected", model[treeiter][0])
You can control what selections are allowed by calling
:meth:`Gtk.TreeSelection.set_mode`.
:meth:`Gtk.TreeSelection.get_selected` does not work if the selection mode is
set to :attr:`Gtk.SelectionMode.MULTIPLE`, use
:meth:`Gtk.TreeSelection.get_selected_rows` instead.
Sorting
-------
Sorting is an important feature for tree views and is supported by the standard tree models (:class:`Gtk.TreeStore` and :class:`Gtk.ListStore`), which implement the :class:`Gtk.TreeSortable` interface.
Sorting by clicking on columns
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
A column of a :class:`Gtk.TreeView` can easily made sortable with a call to :meth:`Gtk.TreeViewColumn.set_sort_column_id`.
Afterwards the column can be sorted by clicking on its header.
First we need a simple :class:`Gtk.TreeView` and a :class:`Gtk.ListStore` as a model.
.. code-block:: python
model = Gtk.ListStore(str)
model.append(["Benjamin"])
model.append(["Charles"])
model.append(["alfred"])
model.append(["Alfred"])
model.append(["David"])
model.append(["charles"])
model.append(["david"])
model.append(["benjamin"])
treeView = Gtk.TreeView(model)
cellRenderer = Gtk.CellRendererText()
column = Gtk.TreeViewColumn("Title", renderer, text=0)
The next step is to enable sorting. Note that the *column_id* (``0`` in the example) refers to the column of the model and **not** to the TreeView's column.
.. code-block:: python
column.set_sort_column_id(0)
Setting a custom sort function
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
It is also possible to set a custom comparison function in order to change the sorting behaviour.
As an example we will create a comparison function that sorts case-sensitive.
In the example above the sorted list looked like::
alfred
Alfred
benjamin
Benjamin
charles
Charles
david
David
The case-sensitive sorted list will look like::
Alfred
Benjamin
Charles
David
alfred
benjamin
charles
david
First of all a comparison function is needed.
This function gets two rows and has to return a negative integer if the first one should come before the second one, zero if they are equal and a positive integer if the second one should come before the second one.
.. code-block:: python
def compare(model, row1, row2, user_data):
sort_column, _ = model.get_sort_column_id()
value1 = model.get_value(row1, sort_column)
value2 = model.get_value(row2, sort_column)
if value1 < value2:
return -1
elif value1 == value2:
return 0
else:
return 1
Then the sort function has to be set by :meth:`Gtk.TreeSortable.set_sort_func`.
.. code-block:: python
model.set_sort_func(0, compare, None)
Filtering
---------
Unlike sorting, filtering is not handled by the two models we previously saw, but by the :class:`Gtk.TreeModelFilter` class. This class, like :class:`Gtk.TreeStore` and :class:`Gtk.ListStore`, is a :class:`Gtk.TreeModel`. It acts as a layer between the "real" model (a :class:`Gtk.TreeStore` or a :class:`Gtk.ListStore`), hiding some elements to the view. In practice, it supplies the :class:`Gtk.TreeView` with a subset of the underlying model. Instances of :class:`Gtk.TreeModelFilter` can be stacked one onto another, to use multiple filters on the same model (in the same way you'd use "AND" clauses in a SQL request). They can also be chained with :class:`Gtk.TreeModelSort` instances.
You can create a new instance of a :class:`Gtk.TreeModelFilter` and give it a model to filter, but the easiest way is to spawn it directly from the filtered model, using the :meth:`Gtk.TreeModel.filter_new` method.
.. code-block:: python
filter = model.filter_new()
In the same way the sorting function works, the :class:`Gtk.TreeModelFilter` needs a "visibility" function, which, given a row from the underlying model, will return a boolean indicating if this row should be filtered out or not. It's set by :meth:`Gtk.TreeModelFilter.set_visible_func`:
.. code-block:: python
filter.set_visible_func(filter_func, data=None)
Let's look at a full example which uses the whole :class:`Gtk.ListStore` - :class:`Gtk.TreeModelFilter` - :class:`Gtk.TreeModelFilter` - :class:`Gtk.TreeView` stack.
.. image:: ../images/treeview_filter_example.png
.. literalinclude:: ../examples/treeview_filter_example.py
:linenos: