Table Of Contents
Source code for kivy.uix.widget
'''
Widget class
============
The :class:`Widget` class is the base class required for creating Widgets.
This widget class was designed with a couple of principles in mind:
* *Event Driven*
Widget interaction is built on top of events that occur. If a property
changes, the widget can respond to the change in the 'on_<propname>'
callback. If nothing changes, nothing will be done. That's the main
goal of the :class:`~kivy.properties.Property` class.
* *Separation Of Concerns (the widget and its graphical representation)*
Widgets don't have a `draw()` method. This is done on purpose: The idea
is to allow you to create your own graphical representation outside the
widget class.
Obviously you can still use all the available properties to do that, so
that your representation properly reflects the widget's current state.
Every widget has its own :class:`~kivy.graphics.Canvas` that you
can use to draw. This separation allows Kivy to run your
application in a very efficient manner.
* *Bounding Box / Collision*
Often you want to know if a certain point is within the bounds of your
widget. An example would be a button widget where you only want to
trigger an action when the button itself is actually touched.
For this, you can use the :meth:`~Widget.collide_point` method, which
will return True if the point you pass to it is inside the axis-aligned
bounding box defined by the widget's position and size.
If a simple AABB is not sufficient, you can override the method to
perform the collision checks with more complex shapes, e.g. a polygon.
You can also check if a widget collides with another widget with
:meth:`~Widget.collide_widget`.
We also have some default values and behaviors that you should be aware of:
* A :class:`Widget` is not a :class:`~kivy.uix.layout.Layout`: it will not
change the position or the size of its children. If you want control over
positioning or sizing, use a :class:`~kivy.uix.layout.Layout`.
* The default size of a widget is (100, 100). This is only changed if the
parent is a :class:`~kivy.uix.layout.Layout`.
For example, if you add a :class:`Label` inside a
:class:`Button`, the label will not inherit the button's size or position
because the button is not a *Layout*: it's just another *Widget*.
* The default size_hint is (1, 1). If the parent is a :class:`Layout`, then the
widget size will be the parent layout's size.
* :meth:`~Widget.on_touch_down`, :meth:`~Widget.on_touch_move`,
:meth:`~Widget.on_touch_up` don't do any sort of collisions. If you want to
know if the touch is inside your widget, use :meth:`~Widget.collide_point`.
Using Properties
----------------
When you read the documentation, all properties are described in the format::
<name> is a <property class> and defaults to <default value>.
e.g.
:attr:`~kivy.uix.label.Label.text` is a
:class:`~kivy.properties.StringProperty` and defaults to ''.
If you want to be notified when the pos attribute changes, i.e. when the
widget moves, you can bind your own callback function like this::
def callback_pos(instance, value):
print('The widget', instance, 'moved to', value)
wid = Widget()
wid.bind(pos=callback_pos)
Read more about :doc:`/api-kivy.properties`.
Basic drawing
-------------
Widgets support a range of drawing instructions that you can use to customize
the look of your widgets and layouts. For example, to draw a background image
for your widget, you can do the following:
.. code-block:: python
def redraw(self, args):
self.bg_rect.size = self.size
self.bg_rect.pos = self.pos
widget = Widget()
with widget.canvas:
widget.bg_rect = Rectangle(source="cover.jpg", pos=self.pos, \
size=self.size)
widget.bind(pos=redraw, size=redraw)
To draw a background in kv:
.. code-block:: kv
Widget:
canvas:
Rectangle:
source: "cover.jpg"
size: self.size
pos: self.pos
These examples only scratch the surface. Please see the :mod:`kivy.graphics`
documentation for more information.
.. _widget-event-bubbling:
Widget touch event bubbling
---------------------------
When you catch touch events between multiple widgets, you often
need to be aware of the order in which these events are propagated. In Kivy,
events bubble up from the first child upwards through the other children.
If a widget has children, the event is passed through its children before
being passed on to the widget after it.
As the :meth:`~kivy.uix.widget.Widget.on_touch_up` method inserts widgets at
index 0 by default, this means the event goes from the most recently added
widget back to the first one added. Consider the following:
.. code-block:: python
box = BoxLayout()
box.add_widget(Label(text="a"))
box.add_widget(Label(text="b"))
box.add_widget(Label(text="c"))
The label with text "c" gets the event first, "b" second and "a" last. You can
reverse this order by manually specifying the index:
.. code-block:: python
box = BoxLayout()
box.add_widget(Label(text="a"), index=0)
box.add_widget(Label(text="b"), index=1)
box.add_widget(Label(text="c"), index=2)
Now the order would be "a", "b" then "c". One thing to keep in mind when using
kv is that declaring a widget uses the
:meth:`~kivy.uix.widget.Widget.add_widget` method for insertion. Hence, using
.. code-block:: kv
BoxLayout:
MyLabel:
text: "a"
MyLabel:
text: "b"
MyLabel:
text: "c"
would result in the event order "c", "b" then "a" as "c" was actually the last
added widget. It thus has index 0, "b" index 1 and "a" index 2. Effectively,
the child order is the reverse of its listed order.
This ordering is the same for the :meth:`~kivy.uix.widget.Widget.on_touch_move`
and :meth:`~kivy.uix.widget.Widget.on_touch_up` events.
In order to stop this event bubbling, a method can return `True`. This tells
Kivy the event has been handled and the event propagation stops. For example:
.. code-block:: python
class MyWidget(Widget):
def on_touch_down(self, touch):
If <some_condition>:
# Do stuff here and kill the event
return True
else:
return super(MyWidget, self).on_touch_down(touch)
This approach gives you good control over exactly how events are dispatched
and managed. Sometimes, however, you may wish to let the event be completely
propagated before taking action. You can use the
:class:`~kivy.clock.Clock` to help you here:
.. code-block:: python
class MyWidget(Label):
def on_touch_down(self, touch, after=False):
if after:
print "Fired after the event has been dispatched!"
else:
Clock.schedule_once(lambda dt: self.on_touch_down(touch, True))
return super(MyWidget, self).on_touch_down(touch)
Usage of :attr:`Widget.center`, :attr:`Widget.right`, and :attr:`Widget.top`
----------------------------------------------------------------------------
A common mistake when using one of the computed properties such as
:attr:`Widget.right` is to use it to make a widget follow its parent with a
KV rule such as `right: self.parent.right`. Consider, for example:
.. code-block:: kv
FloatLayout:
id: layout
width: 100
Widget:
id: wid
right: layout.right
The (mistaken) expectation is that this rule ensures that wid's right will
always be whatever layout's right is - that is wid.right and layout.right will
always be identical. In actual fact, this rule only says that "whenever
layout's `right` changes, wid's right will be set to that value". The
difference being that as long as `layout.right` doesn't change, `wid.right`
could be anything, even a value that will make them different.
Specifically, for the KV code above, consider the following example::
>>> print(layout.right, wid.right)
(100, 100)
>>> wid.x = 200
>>> print(layout.right, wid.right)
(100, 300)
As can be seen, initially they are in sync, however, when we change `wid.x`
they go out of sync because `layout.right` is not changed and the rule is not
triggered.
The proper way to make the widget follow its parent's right is to use
:attr:`Widget.pos_hint`. If instead of `right: layout.right` we did
`pos_hint: {'right': 1}`, then the widgets right will always be set to be
at the parent's right at each layout update.
'''
__all__ = ('Widget', 'WidgetException')
from kivy.event import EventDispatcher
from kivy.factory import Factory
from kivy.properties import (
NumericProperty, StringProperty, AliasProperty, ReferenceListProperty,
ObjectProperty, ListProperty, DictProperty, BooleanProperty)
from kivy.graphics import (
Canvas, Translate, Fbo, ClearColor, ClearBuffers, Scale)
from kivy.graphics.transformation import Matrix
from kivy.base import EventLoop
from kivy.lang import Builder
from kivy.context import get_current_context
from kivy.weakproxy import WeakProxy
from functools import partial
from itertools import islice
# References to all the widget destructors (partial method with widget uid as
# key).
_widget_destructors = {}
def _widget_destructor(uid, r):
# Internal method called when a widget is deleted from memory. the only
# thing we remember about it is its uid. Clear all the associated callbacks
# created in kv language.
del _widget_destructors[uid]
Builder.unbind_widget(uid)
class WidgetMetaclass(type):
'''Metaclass to automatically register new widgets for the
:class:`~kivy.factory.Factory`.
.. warning::
This metaclass is used by the Widget. Do not use it directly!
'''
def __init__(mcs, name, bases, attrs):
super(WidgetMetaclass, mcs).__init__(name, bases, attrs)
Factory.register(name, cls=mcs)
#: Base class used for Widget, that inherits from :class:`EventDispatcher`
WidgetBase = WidgetMetaclass('WidgetBase', (EventDispatcher, ), {})
[docs]class Widget(WidgetBase):
'''Widget class. See module documentation for more information.
:Events:
`on_touch_down`: `(touch, )`
Fired when a new touch event occurs. `touch` is the touch object.
`on_touch_move`: `(touch, )`
Fired when an existing touch moves. `touch` is the touch object.
`on_touch_up`: `(touch, )`
Fired when an existing touch disappears. `touch` is the touch
object.
`on_kv_post`: `(base_widget, )`
Fired after all the kv rules associated with the widget
and all other widgets that are in any of those rules have had
all their kv rules applied. `base_widget` is the base-most widget
whose instantiation triggered the kv rules (i.e. the widget
instantiated from Python, e.g. ``MyWidget()``).
.. versionchanged:: 1.11.0
.. warning::
Adding a `__del__` method to a class derived from Widget with Python
prior to 3.4 will disable automatic garbage collection for instances
of that class. This is because the Widget class creates reference
cycles, thereby `preventing garbage collection
<https://docs.python.org/2/library/gc.html#gc.garbage>`_.
.. versionchanged:: 1.0.9
Everything related to event properties has been moved to the
:class:`~kivy.event.EventDispatcher`. Event properties can now be used
when contructing a simple class without subclassing :class:`Widget`.
.. versionchanged:: 1.5.0
The constructor now accepts on_* arguments to automatically bind
callbacks to properties or events, as in the Kv language.
'''
__metaclass__ = WidgetMetaclass
__events__ = (
'on_touch_down', 'on_touch_move', 'on_touch_up', 'on_kv_post')
_proxy_ref = None
def __init__(self, **kwargs):
# Before doing anything, ensure the windows exist.
EventLoop.ensure_window()
# Assign the default context of the widget creation.
if not hasattr(self, '_context'):
self._context = get_current_context()
no_builder = '__no_builder' in kwargs
self._disabled_value = False
if no_builder:
del kwargs['__no_builder']
on_args = {k: v for k, v in kwargs.items() if k[:3] == 'on_'}
for key in on_args:
del kwargs[key]
self._disabled_count = 0
super(Widget, self).__init__(**kwargs)
# Create the default canvas if it does not exist.
if self.canvas is None:
self.canvas = Canvas(opacity=self.opacity)
# Apply all the styles.
if not no_builder:
rule_children = []
self.apply_class_lang_rules(
ignored_consts=self._kwargs_applied_init,
rule_children=rule_children)
for widget in rule_children:
widget.dispatch('on_kv_post', self)
self.dispatch('on_kv_post', self)
# Bind all the events.
if on_args:
self.bind(**on_args)
@property
def proxy_ref(self):
'''Return a proxy reference to the widget, i.e. without creating a
reference to the widget. See `weakref.proxy
<http://docs.python.org/2/library/weakref.html?highlight\
=proxy#weakref.proxy>`_ for more information.
.. versionadded:: 1.7.2
'''
_proxy_ref = self._proxy_ref
if _proxy_ref is not None:
return _proxy_ref
f = partial(_widget_destructor, self.uid)
self._proxy_ref = _proxy_ref = WeakProxy(self, f)
# Only f should be enough here, but it appears that is a very
# specific case, the proxy destructor is not called if both f and
# _proxy_ref are not together in a tuple.
_widget_destructors[self.uid] = (f, _proxy_ref)
return _proxy_ref
def __hash__(self):
return id(self)
@property
def __self__(self):
return self
[docs] def apply_class_lang_rules(
self, root=None, ignored_consts=set(), rule_children=None):
'''
Method that is called by kivy to apply the kv rules of this widget's
class.
:Parameters:
`root`: :class:`Widget`
The root widget that instantiated this widget in kv, if the
widget was instantiated in kv, otherwise ``None``.
`ignored_consts`: set
(internal) See :meth:`~kivy.lang.builder.BuilderBase.apply`.
`rule_children`: list
(internal) See :meth:`~kivy.lang.builder.BuilderBase.apply`.
This is useful to be able to execute code before/after the class kv
rules are applied to the widget. E.g. if the kv code requires some
properties to be initialized before it is used in a binding rule.
If overwriting remember to call ``super``, otherwise the kv rules will
not be applied.
In the following example,
.. code-block:: python
class MyWidget(Widget):
pass
class OtherWidget(MyWidget):
pass
.. code-block:: kv
<MyWidget>:
my_prop: some_value
<OtherWidget>:
other_prop: some_value
When ``OtherWidget`` is instantiated with ``OtherWidget()``, the
widget's :meth:`apply_class_lang_rules` is called and it applies the
kv rules of this class - ``<MyWidget>`` and ``<OtherWidget>``.
Similarly, when the widget is instantiated from kv, e.g.
.. code-block:: kv
<MyBox@BoxLayout>:
height: 55
OtherWidget:
width: 124
``OtherWidget``'s :meth:`apply_class_lang_rules` is called and it
applies the kv rules of this class - ``<MyWidget>`` and
``<OtherWidget>``.
.. note::
It applies only the class rules not the instance rules. I.e. in the
above kv example in the ``MyBox`` rule when ``OtherWidget`` is
instantiated, its :meth:`apply_class_lang_rules` applies the
``<MyWidget>`` and ``<OtherWidget>`` rules to it - it does not
apply the ``width: 124`` rule. The ``width: 124`` rule is part of
the ``MyBox`` rule and is applied by the ``MyBox``'s instance's
:meth:`apply_class_lang_rules`.
.. versionchanged:: 1.11.0
'''
Builder.apply(
self, ignored_consts=ignored_consts,
rule_children=rule_children)
#
# Collision
#
[docs] def collide_point(self, x, y):
'''
Check if a point (x, y) is inside the widget's axis aligned bounding
box.
:Parameters:
`x`: numeric
x position of the point (in parent coordinates)
`y`: numeric
y position of the point (in parent coordinates)
:Returns:
A bool. True if the point is inside the bounding box, False
otherwise.
.. code-block:: python
>>> Widget(pos=(10, 10), size=(50, 50)).collide_point(40, 40)
True
'''
return self.x <= x <= self.right and self.y <= y <= self.top
[docs] def collide_widget(self, wid):
'''
Check if another widget collides with this widget. This function
performs an axis-aligned bounding box intersection test by default.
:Parameters:
`wid`: :class:`Widget` class
Widget to test collision with.
:Returns:
bool. True if the other widget collides with this widget, False
otherwise.
.. code-block:: python
>>> wid = Widget(size=(50, 50))
>>> wid2 = Widget(size=(50, 50), pos=(25, 25))
>>> wid.collide_widget(wid2)
True
>>> wid2.pos = (55, 55)
>>> wid.collide_widget(wid2)
False
'''
if self.right < wid.x:
return False
if self.x > wid.right:
return False
if self.top < wid.y:
return False
if self.y > wid.top:
return False
return True
#
# Default event handlers
#
[docs] def on_touch_down(self, touch):
'''Receive a touch down event.
:Parameters:
`touch`: :class:`~kivy.input.motionevent.MotionEvent` class
Touch received. The touch is in parent coordinates. See
:mod:`~kivy.uix.relativelayout` for a discussion on
coordinate systems.
:Returns: bool
If True, the dispatching of the touch event will stop.
If False, the event will continue to be dispatched to the rest
of the widget tree.
'''
if self.disabled and self.collide_point(*touch.pos):
return True
for child in self.children[:]:
if child.dispatch('on_touch_down', touch):
return True
[docs] def on_touch_move(self, touch):
'''Receive a touch move event. The touch is in parent coordinates.
See :meth:`on_touch_down` for more information.
'''
if self.disabled:
return
for child in self.children[:]:
if child.dispatch('on_touch_move', touch):
return True
[docs] def on_touch_up(self, touch):
'''Receive a touch up event. The touch is in parent coordinates.
See :meth:`on_touch_down` for more information.
'''
if self.disabled:
return
for child in self.children[:]:
if child.dispatch('on_touch_up', touch):
return True
def on_kv_post(self, base_widget):
pass
#
# Tree management
#
[docs] def add_widget(self, widget, index=0, canvas=None):
'''Add a new widget as a child of this widget.
:Parameters:
`widget`: :class:`Widget`
Widget to add to our list of children.
`index`: int, defaults to 0
Index to insert the widget in the list. Notice that the default
of 0 means the widget is inserted at the beginning of the list
and will thus be drawn on top of other sibling widgets. For a
full discussion of the index and widget hierarchy, please see
the :doc:`Widgets Programming Guide <guide/widgets>`.
.. versionadded:: 1.0.5
`canvas`: str, defaults to None
Canvas to add widget's canvas to. Can be 'before', 'after' or
None for the default canvas.
.. versionadded:: 1.9.0
.. code-block:: python
>>> from kivy.uix.button import Button
>>> from kivy.uix.slider import Slider
>>> root = Widget()
>>> root.add_widget(Button())
>>> slider = Slider()
>>> root.add_widget(slider)
'''
if not isinstance(widget, Widget):
raise WidgetException(
'add_widget() can be used only with instances'
' of the Widget class.')
widget = widget.__self__
if widget is self:
raise WidgetException(
'Widget instances cannot be added to themselves.')
parent = widget.parent
# Check if the widget is already a child of another widget.
if parent:
raise WidgetException('Cannot add %r, it already has a parent %r'
% (widget, parent))
widget.parent = parent = self
# Child will be disabled if added to a disabled parent.
widget.inc_disabled(self._disabled_count)
canvas = self.canvas.before if canvas == 'before' else \
self.canvas.after if canvas == 'after' else self.canvas
if index == 0 or len(self.children) == 0:
self.children.insert(0, widget)
canvas.add(widget.canvas)
else:
canvas = self.canvas
children = self.children
if index >= len(children):
index = len(children)
next_index = canvas.indexof(children[-1].canvas)
else:
next_child = children[index]
next_index = canvas.indexof(next_child.canvas)
if next_index == -1:
next_index = canvas.length()
else:
next_index += 1
children.insert(index, widget)
# We never want to insert widget _before_ canvas.before.
if next_index == 0 and canvas.has_before:
next_index = 1
canvas.insert(next_index, widget.canvas)
[docs] def remove_widget(self, widget):
'''Remove a widget from the children of this widget.
:Parameters:
`widget`: :class:`Widget`
Widget to remove from our children list.
.. code-block:: python
>>> from kivy.uix.button import Button
>>> root = Widget()
>>> button = Button()
>>> root.add_widget(button)
>>> root.remove_widget(button)
'''
if widget not in self.children:
return
self.children.remove(widget)
if widget.canvas in self.canvas.children:
self.canvas.remove(widget.canvas)
elif widget.canvas in self.canvas.after.children:
self.canvas.after.remove(widget.canvas)
elif widget.canvas in self.canvas.before.children:
self.canvas.before.remove(widget.canvas)
widget.parent = None
widget.dec_disabled(self._disabled_count)
[docs] def clear_widgets(self, children=None):
'''
Remove all (or the specified) :attr:`~Widget.children` of this widget.
If the 'children' argument is specified, it should be a list (or
filtered list) of children of the current widget.
.. versionchanged:: 1.8.0
The `children` argument can be used to specify the children you
want to remove.
'''
if not children:
children = self.children
remove_widget = self.remove_widget
for child in children[:]:
remove_widget(child)
[docs] def export_to_png(self, filename, *args, **kwargs):
'''Saves an image of the widget and its children in png format at the
specified filename. Works by removing the widget canvas from its
parent, rendering to an :class:`~kivy.graphics.fbo.Fbo`, and calling
:meth:`~kivy.graphics.texture.Texture.save`.
.. note::
The image includes only this widget and its children. If you want
to include widgets elsewhere in the tree, you must call
:meth:`~Widget.export_to_png` from their common parent, or use
:meth:`~kivy.core.window.WindowBase.screenshot` to capture the
whole window.
.. note::
The image will be saved in png format, you should include the
extension in your filename.
.. versionadded:: 1.9.0
:Parameters:
`filename`: str
The filename with which to save the png.
`scale`: float
The amount by which to scale the saved image, defaults to 1.
.. versionadded:: 1.11.0
'''
self.export_as_image().save(filename, flipped=False)
[docs] def export_as_image(self, *args, **kwargs):
'''Return an core :class:`~kivy.core.image.Image` of the actual
widget.
.. versionadded:: 1.11.0
'''
from kivy.core.image import Image
scale = kwargs.get('scale', 1)
if self.parent is not None:
canvas_parent_index = self.parent.canvas.indexof(self.canvas)
if canvas_parent_index > -1:
self.parent.canvas.remove(self.canvas)
fbo = Fbo(size=(self.width * scale, self.height * scale),
with_stencilbuffer=True)
with fbo:
ClearColor(0, 0, 0, 0)
ClearBuffers()
Scale(1, -1, 1)
Scale(scale, scale, 1)
Translate(-self.x, -self.y - self.height, 0)
fbo.add(self.canvas)
fbo.draw()
img = Image(fbo.texture)
fbo.remove(self.canvas)
if self.parent is not None and canvas_parent_index > -1:
self.parent.canvas.insert(canvas_parent_index, self.canvas)
return img
[docs] def get_root_window(self):
'''Return the root window.
:Returns:
Instance of the root window. Can be a
:class:`~kivy.core.window.WindowBase` or
:class:`Widget`.
'''
if self.parent:
return self.parent.get_root_window()
[docs] def get_parent_window(self):
'''Return the parent window.
:Returns:
Instance of the parent window. Can be a
:class:`~kivy.core.window.WindowBase` or
:class:`Widget`.
'''
if self.parent:
return self.parent.get_parent_window()
def _walk(self, restrict=False, loopback=False, index=None):
# We pass index only when we are going on the parent
# so don't yield the parent as well.
if index is None:
index = len(self.children)
yield self
for child in reversed(self.children[:index]):
for walk_child in child._walk(restrict=True):
yield walk_child
# If we want to continue with our parent, just do it.
if not restrict:
parent = self.parent
try:
if parent is None or not isinstance(parent, Widget):
raise ValueError
index = parent.children.index(self)
except ValueError:
# Self is root, if we want to loopback from the first element:
if not loopback:
return
# If we started with root (i.e. index==None), then we have to
# start from root again, so we return self again. Otherwise, we
# never returned it, so return it now starting with it.
parent = self
index = None
for walk_child in parent._walk(loopback=loopback, index=index):
yield walk_child
[docs] def walk(self, restrict=False, loopback=False):
''' Iterator that walks the widget tree starting with this widget and
goes forward returning widgets in the order in which layouts display
them.
:Parameters:
`restrict`: bool, defaults to False
If True, it will only iterate through the widget and its
children (or children of its children etc.). Defaults to False.
`loopback`: bool, defaults to False
If True, when the last widget in the tree is reached,
it'll loop back to the uppermost root and start walking until
we hit this widget again. Naturally, it can only loop back when
`restrict` is False. Defaults to False.
:return:
A generator that walks the tree, returning widgets in the
forward layout order.
For example, given a tree with the following structure:
.. code-block:: kv
GridLayout:
Button
BoxLayout:
id: box
Widget
Button
Widget
walking this tree:
.. code-block:: python
>>> # Call walk on box with loopback True, and restrict False
>>> [type(widget) for widget in box.walk(loopback=True)]
[<class 'BoxLayout'>, <class 'Widget'>, <class 'Button'>,
<class 'Widget'>, <class 'GridLayout'>, <class 'Button'>]
>>> # Now with loopback False, and restrict False
>>> [type(widget) for widget in box.walk()]
[<class 'BoxLayout'>, <class 'Widget'>, <class 'Button'>,
<class 'Widget'>]
>>> # Now with restrict True
>>> [type(widget) for widget in box.walk(restrict=True)]
[<class 'BoxLayout'>, <class 'Widget'>, <class 'Button'>]
.. versionadded:: 1.9.0
'''
gen = self._walk(restrict, loopback)
yield next(gen)
for node in gen:
if node is self:
return
yield node
def _walk_reverse(self, loopback=False, go_up=False):
# process is walk up level, walk down its children tree, then walk up
# next level etc.
# default just walk down the children tree
root = self
index = 0
# we need to go up a level before walking tree
if go_up:
root = self.parent
try:
if root is None or not isinstance(root, Widget):
raise ValueError
index = root.children.index(self) + 1
except ValueError:
if not loopback:
return
index = 0
go_up = False
root = self
# now walk children tree starting with last-most child
for child in islice(root.children, index, None):
for walk_child in child._walk_reverse(loopback=loopback):
yield walk_child
# we need to return ourself last, in all cases
yield root
# if going up, continue walking up the parent tree
if go_up:
for walk_child in root._walk_reverse(loopback=loopback,
go_up=go_up):
yield walk_child
[docs] def walk_reverse(self, loopback=False):
''' Iterator that walks the widget tree backwards starting with the
widget before this, and going backwards returning widgets in the
reverse order in which layouts display them.
This walks in the opposite direction of :meth:`walk`, so a list of the
tree generated with :meth:`walk` will be in reverse order compared
to the list generated with this, provided `loopback` is True.
:Parameters:
`loopback`: bool, defaults to False
If True, when the uppermost root in the tree is
reached, it'll loop back to the last widget and start walking
back until after we hit widget again. Defaults to False.
:return:
A generator that walks the tree, returning widgets in the
reverse layout order.
For example, given a tree with the following structure:
.. code-block:: kv
GridLayout:
Button
BoxLayout:
id: box
Widget
Button
Widget
walking this tree:
.. code-block:: python
>>> # Call walk on box with loopback True
>>> [type(widget) for widget in box.walk_reverse(loopback=True)]
[<class 'Button'>, <class 'GridLayout'>, <class 'Widget'>,
<class 'Button'>, <class 'Widget'>, <class 'BoxLayout'>]
>>> # Now with loopback False
>>> [type(widget) for widget in box.walk_reverse()]
[<class 'Button'>, <class 'GridLayout'>]
>>> forward = [w for w in box.walk(loopback=True)]
>>> backward = [w for w in box.walk_reverse(loopback=True)]
>>> forward == backward[::-1]
True
.. versionadded:: 1.9.0
'''
for node in self._walk_reverse(loopback=loopback, go_up=True):
yield node
if node is self:
return
[docs] def to_widget(self, x, y, relative=False):
'''Convert the given coordinate from window to local widget
coordinates. See :mod:`~kivy.uix.relativelayout` for details on the
coordinate systems.
'''
if self.parent:
x, y = self.parent.to_widget(x, y)
return self.to_local(x, y, relative=relative)
[docs] def to_window(self, x, y, initial=True, relative=False):
'''Transform local coordinates to window coordinates. See
:mod:`~kivy.uix.relativelayout` for details on the coordinate systems.
'''
if not initial:
x, y = self.to_parent(x, y, relative=relative)
if self.parent:
return self.parent.to_window(x, y, initial=False,
relative=relative)
return (x, y)
[docs] def to_parent(self, x, y, relative=False):
'''Transform local coordinates to parent coordinates. See
:mod:`~kivy.uix.relativelayout` for details on the coordinate systems.
:Parameters:
`relative`: bool, defaults to False
Change to True if you want to translate relative positions from
a widget to its parent coordinates.
'''
if relative:
return (x + self.x, y + self.y)
return (x, y)
[docs] def to_local(self, x, y, relative=False):
'''Transform parent coordinates to local coordinates. See
:mod:`~kivy.uix.relativelayout` for details on the coordinate systems.
:Parameters:
`relative`: bool, defaults to False
Change to True if you want to translate coordinates to
relative widget coordinates.
'''
if relative:
return (x - self.x, y - self.y)
return (x, y)
def _apply_transform(self, m, pos=None):
if self.parent:
x, y = self.parent.to_widget(relative=True,
*self.to_window(*(pos or self.pos)))
m.translate(x, y, 0)
m = self.parent._apply_transform(m) if self.parent else m
return m
[docs] def get_window_matrix(self, x=0, y=0):
'''Calculate the transformation matrix to convert between window and
widget coordinates.
:Parameters:
`x`: float, defaults to 0
Translates the matrix on the x axis.
`y`: float, defaults to 0
Translates the matrix on the y axis.
'''
m = Matrix()
m.translate(x, y, 0)
m = self._apply_transform(m)
return m
x = NumericProperty(0)
'''X position of the widget.
:attr:`x` is a :class:`~kivy.properties.NumericProperty` and defaults to 0.
'''
y = NumericProperty(0)
'''Y position of the widget.
:attr:`y` is a :class:`~kivy.properties.NumericProperty` and defaults to 0.
'''
width = NumericProperty(100)
'''Width of the widget.
:attr:`width` is a :class:`~kivy.properties.NumericProperty` and defaults
to 100.
.. warning::
Keep in mind that the `width` property is subject to layout logic and
that this has not yet happened at the time of the widget's `__init__`
method.
'''
height = NumericProperty(100)
'''Height of the widget.
:attr:`height` is a :class:`~kivy.properties.NumericProperty` and defaults
to 100.
.. warning::
Keep in mind that the `height` property is subject to layout logic and
that this has not yet happened at the time of the widget's `__init__`
method.
'''
pos = ReferenceListProperty(x, y)
'''Position of the widget.
:attr:`pos` is a :class:`~kivy.properties.ReferenceListProperty` of
(:attr:`x`, :attr:`y`) properties.
'''
size = ReferenceListProperty(width, height)
'''Size of the widget.
:attr:`size` is a :class:`~kivy.properties.ReferenceListProperty` of
(:attr:`width`, :attr:`height`) properties.
'''
def get_right(self):
return self.x + self.width
def set_right(self, value):
self.x = value - self.width
right = AliasProperty(get_right, set_right,
bind=('x', 'width'),
cache=True)
'''Right position of the widget.
:attr:`right` is an :class:`~kivy.properties.AliasProperty` of
(:attr:`x` + :attr:`width`).
'''
def get_top(self):
return self.y + self.height
def set_top(self, value):
self.y = value - self.height
top = AliasProperty(get_top, set_top,
bind=('y', 'height'),
cache=True)
'''Top position of the widget.
:attr:`top` is an :class:`~kivy.properties.AliasProperty` of
(:attr:`y` + :attr:`height`).
'''
def get_center_x(self):
return self.x + self.width / 2.
def set_center_x(self, value):
self.x = value - self.width / 2.
center_x = AliasProperty(get_center_x, set_center_x,
bind=('x', 'width'),
cache=True)
'''X center position of the widget.
:attr:`center_x` is an :class:`~kivy.properties.AliasProperty` of
(:attr:`x` + :attr:`width` / 2.).
'''
def get_center_y(self):
return self.y + self.height / 2.
def set_center_y(self, value):
self.y = value - self.height / 2.
center_y = AliasProperty(get_center_y, set_center_y,
bind=('y', 'height'),
cache=True)
'''Y center position of the widget.
:attr:`center_y` is an :class:`~kivy.properties.AliasProperty` of
(:attr:`y` + :attr:`height` / 2.).
'''
center = ReferenceListProperty(center_x, center_y)
'''Center position of the widget.
:attr:`center` is a :class:`~kivy.properties.ReferenceListProperty` of
(:attr:`center_x`, :attr:`center_y`) properties.
'''
cls = ListProperty([])
'''Class of the widget, used for styling.
'''
id = StringProperty(None, allownone=True, deprecated=True)
'''Identifier of the widget in the tree.
:attr:`id` is a :class:`~kivy.properties.StringProperty` and defaults to
None.
.. note::
The :attr:`id` is not the same as ``id`` in the kv language. For the
latter, see :attr:`ids` and :ref:`Kivy Language: ids <kv-lang-ids>`.
.. warning::
The :attr:`id` property has been deprecated and will be removed
completely in future versions.
'''
children = ListProperty([])
'''List of children of this widget.
:attr:`children` is a :class:`~kivy.properties.ListProperty` and
defaults to an empty list.
Use :meth:`add_widget` and :meth:`remove_widget` for manipulating the
children list. Don't manipulate the children list directly unless you know
what you are doing.
'''
parent = ObjectProperty(None, allownone=True, rebind=True)
'''Parent of this widget. The parent of a widget is set when the widget
is added to another widget and unset when the widget is removed from its
parent.
:attr:`parent` is an :class:`~kivy.properties.ObjectProperty` and
defaults to None.
'''
size_hint_x = NumericProperty(1, allownone=True)
'''x size hint. Represents how much space the widget should use in the
direction of the x axis relative to its parent's width.
Only the :class:`~kivy.uix.layout.Layout` and
:class:`~kivy.core.window.Window` classes make use of the hint.
The size_hint is used by layouts for two purposes:
- When the layout considers widgets on their own rather than in
relation to its other children, the size_hint_x is a direct proportion
of the parent width, normally between 0.0 and 1.0. For instance, a
widget with ``size_hint_x=0.5`` in
a vertical BoxLayout will take up half the BoxLayout's width, or
a widget in a FloatLayout with ``size_hint_x=0.2`` will take up 20%
of the FloatLayout width. If the size_hint is greater than 1, the
widget will be wider than the parent.
- When multiple widgets can share a row of a layout, such as in a
horizontal BoxLayout, their widths will be their size_hint_x as a
fraction of the sum of widget size_hints. For instance, if the
size_hint_xs are (0.5, 1.0, 0.5), the first widget will have a
width of 25% of the parent width.
:attr:`size_hint_x` is a :class:`~kivy.properties.NumericProperty` and
defaults to 1.
'''
size_hint_y = NumericProperty(1, allownone=True)
'''y size hint.
:attr:`size_hint_y` is a :class:`~kivy.properties.NumericProperty` and
defaults to 1.
See :attr:`size_hint_x` for more information, but with widths and heights
swapped.
'''
size_hint = ReferenceListProperty(size_hint_x, size_hint_y)
'''Size hint.
:attr:`size_hint` is a :class:`~kivy.properties.ReferenceListProperty` of
(:attr:`size_hint_x`, :attr:`size_hint_y`) properties.
See :attr:`size_hint_x` for more information.
'''
pos_hint = ObjectProperty({})
'''Position hint. This property allows you to set the position of
the widget inside its parent layout, in percent (similar to
size_hint).
For example, if you want to set the top of the widget to be at 90%
height of its parent layout, you can write::
widget = Widget(pos_hint={'top': 0.9})
The keys 'x', 'right' and 'center_x' will use the parent width.
The keys 'y', 'top' and 'center_y' will use the parent height.
See :doc:`api-kivy.uix.floatlayout` for further reference.
.. note::
:attr:`pos_hint` is not used by all layouts. Check the documentation
of the layout in question to see if it supports pos_hint.
:attr:`pos_hint` is an :class:`~kivy.properties.ObjectProperty`
containing a dict.
'''
size_hint_min_x = NumericProperty(None, allownone=True)
'''When not None, the x-direction minimum size (in pixels,
like :attr:`width`) when :attr:`size_hint_x` is also not None.
When :attr:`size_hint_x` is not None, it is the minimum width that the
widget will be set due to the :attr:`size_hint_x`. I.e. when a smaller size
would be set, :attr:`size_hint_min_x` is the value used instead for the
widget width. When None, or when :attr:`size_hint_x` is None,
:attr:`size_hint_min_x` doesn't do anything.
Only the :class:`~kivy.uix.layout.Layout` and
:class:`~kivy.core.window.Window` classes make use of the hint.
:attr:`size_hint_min_x` is a :class:`~kivy.properties.NumericProperty` and
defaults to None.
.. versionadded:: 1.10.0
'''
size_hint_min_y = NumericProperty(None, allownone=True)
'''When not None, the y-direction minimum size (in pixels,
like :attr:`height`) when :attr:`size_hint_y` is also not None.
When :attr:`size_hint_y` is not None, it is the minimum height that the
widget will be set due to the :attr:`size_hint_y`. I.e. when a smaller size
would be set, :attr:`size_hint_min_y` is the value used instead for the
widget height. When None, or when :attr:`size_hint_y` is None,
:attr:`size_hint_min_y` doesn't do anything.
Only the :class:`~kivy.uix.layout.Layout` and
:class:`~kivy.core.window.Window` classes make use of the hint.
:attr:`size_hint_min_y` is a :class:`~kivy.properties.NumericProperty` and
defaults to None.
.. versionadded:: 1.10.0
'''
size_hint_min = ReferenceListProperty(size_hint_min_x, size_hint_min_y)
'''Minimum size when using :attr:`size_hint`.
:attr:`size_hint_min` is a :class:`~kivy.properties.ReferenceListProperty`
of (:attr:`size_hint_min_x`, :attr:`size_hint_min_y`) properties.
.. versionadded:: 1.10.0
'''
size_hint_max_x = NumericProperty(None, allownone=True)
'''When not None, the x-direction maximum size (in pixels,
like :attr:`width`) when :attr:`size_hint_x` is also not None.
Similar to :attr:`size_hint_min_x`, except that it sets the maximum width.
:attr:`size_hint_max_x` is a :class:`~kivy.properties.NumericProperty` and
defaults to None.
.. versionadded:: 1.10.0
'''
size_hint_max_y = NumericProperty(None, allownone=True)
'''When not None, the y-direction maximum size (in pixels,
like :attr:`height`) when :attr:`size_hint_y` is also not None.
Similar to :attr:`size_hint_min_y`, except that it sets the maximum height.
:attr:`size_hint_max_y` is a :class:`~kivy.properties.NumericProperty` and
defaults to None.
.. versionadded:: 1.10.0
'''
size_hint_max = ReferenceListProperty(size_hint_max_x, size_hint_max_y)
'''Maximum size when using :attr:`size_hint`.
:attr:`size_hint_max` is a :class:`~kivy.properties.ReferenceListProperty`
of (:attr:`size_hint_max_x`, :attr:`size_hint_max_y`) properties.
.. versionadded:: 1.10.0
'''
ids = DictProperty({})
'''This is a dictionary of ids defined in your kv language. This will only
be populated if you use ids in your kv language code.
.. versionadded:: 1.7.0
:attr:`ids` is a :class:`~kivy.properties.DictProperty` and defaults to an
empty dict {}.
The :attr:`ids` are populated for each root level widget definition. For
example:
.. code-block:: kv
# in kv
<MyWidget@Widget>:
id: my_widget
Label:
id: label_widget
Widget:
id: inner_widget
Label:
id: inner_label
TextInput:
id: text_input
OtherWidget:
id: other_widget
<OtherWidget@Widget>
id: other_widget
Label:
id: other_label
TextInput:
id: other_textinput
Then, in python:
.. code-block:: python
>>> widget = MyWidget()
>>> print(widget.ids)
{'other_widget': <weakproxy at 041CFED0 to OtherWidget at 041BEC38>,
'inner_widget': <weakproxy at 04137EA0 to Widget at 04138228>,
'inner_label': <weakproxy at 04143540 to Label at 04138260>,
'label_widget': <weakproxy at 04137B70 to Label at 040F97A0>,
'text_input': <weakproxy at 041BB5D0 to TextInput at 041BEC00>}
>>> print(widget.ids['other_widget'].ids)
{'other_textinput': <weakproxy at 041DBB40 to TextInput at 041BEF48>,
'other_label': <weakproxy at 041DB570 to Label at 041BEEA0>}
>>> print(widget.ids['label_widget'].ids)
{}
'''
opacity = NumericProperty(1.0)
'''Opacity of the widget and all its children.
.. versionadded:: 1.4.1
The opacity attribute controls the opacity of the widget and its children.
Be careful, it's a cumulative attribute: the value is multiplied by the
current global opacity and the result is applied to the current context
color.
For example, if the parent has an opacity of 0.5 and a child has an
opacity of 0.2, the real opacity of the child will be 0.5 * 0.2 = 0.1.
Then, the opacity is applied by the shader as:
.. code-block:: python
frag_color = color * vec4(1.0, 1.0, 1.0, opacity);
:attr:`opacity` is a :class:`~kivy.properties.NumericProperty` and defaults
to 1.0.
'''
def on_opacity(self, instance, value):
canvas = self.canvas
if canvas is not None:
canvas.opacity = value
canvas = None
'''Canvas of the widget.
The canvas is a graphics object that contains all the drawing instructions
for the graphical representation of the widget.
There are no general properties for the Widget class, such as background
color, to keep the design simple and lean. Some derived classes, such as
Button, do add such convenience properties but generally the developer is
responsible for implementing the graphics representation for a custom
widget from the ground up. See the derived widget classes for patterns to
follow and extend.
See :class:`~kivy.graphics.Canvas` for more information about the usage.
'''
def get_disabled(self):
return self._disabled_count > 0
def set_disabled(self, value):
if value != self._disabled_value:
self._disabled_value = value
if value:
self.inc_disabled()
else:
self.dec_disabled()
return True
def inc_disabled(self, count=1):
self._disabled_count += count
if self._disabled_count - count < 1 <= self._disabled_count:
self.property('disabled').dispatch(self)
for c in self.children:
c.inc_disabled(count)
def dec_disabled(self, count=1):
self._disabled_count -= count
if self._disabled_count <= 0 < self._disabled_count + count:
self.property('disabled').dispatch(self)
for c in self.children:
c.dec_disabled(count)
disabled = AliasProperty(get_disabled, set_disabled)
'''Indicates whether this widget can interact with input or not.
:attr:`disabled` is an :class:`~kivy.properties.AliasProperty` and
defaults to False.
.. note::
1. Child Widgets, when added to a disabled widget, will be disabled
automatically.
2. Disabling/enabling a parent disables/enables all
of its children.
.. versionadded:: 1.8.0
.. versionchanged:: 1.10.1
:attr:`disabled` was changed from a
:class:`~kivy.properties.BooleanProperty` to an
:class:`~kivy.properties.AliasProperty` to allow access to its
previous state when a parent's disabled state is changed.
'''