/
widget.py
617 lines (475 loc) · 19.7 KB
/
widget.py
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'''
Widget class
============
The :class:`Widget` class is the base class required to create a Widget.
Our widget class is designed with a couple of principles in mind:
Event Driven
The widget interaction is built on top of events that occur.
If a property changes, the widget can do something. If nothing changes
in the widget, nothing will be done. That's the main goal of the
:class:`~kivy.properties.Property` class.
Separate 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 want to only
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 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 defaults that you should be aware of:
* A :class:`Widget` is not a :class:`Layout`: it will not change the position
nor the size of its children. If you want a better positionning / sizing, use
a :class:`Layout`.
* The default size is (100, 100), if the parent is not a :class:`Layout`. For
example, adding a widget inside a :class:`Button`, :class:`Label`, will not
inherit from the parent size or pos.
* The default size_hint is (1, 1). If the parent is a :class:`Layout`, then the
widget size will be the parent/layout 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>, defaults to <default value>
For example::
:data:`Widget.pos` is a :class:`~kivy.properties.ReferenceListProperty` of
(:data:`Widget.x`, :data:`Widget.y`) properties.
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 the :doc:`/api-kivy.properties`.
'''
__all__ = ('Widget', 'WidgetException')
from kivy.event import EventDispatcher
from kivy.factory import Factory
from kivy.properties import NumericProperty, StringProperty, \
AliasProperty, ReferenceListProperty, ObjectProperty, \
ListProperty, DictProperty
from kivy.graphics import Canvas
from kivy.base import EventLoop
from kivy.lang import Builder
class WidgetException(Exception):
'''Fired when the widget gets an exception.
'''
pass
class WidgetMetaclass(type):
'''Metaclass to auto register new widget into :class:`~kivy.factory.Factory`
.. warning::
This metaclass is used for Widget. Don't use it directly !
'''
def __init__(mcs, name, bases, attrs):
super(WidgetMetaclass, mcs).__init__(name, bases, attrs)
Factory.register(name, cls=mcs)
class Widget(EventDispatcher):
'''Widget class. See module documentation for more information.
:Events:
`on_touch_down`:
Fired when a new touch happens
`on_touch_move`:
Fired when an existing touch is moved
`on_touch_up`:
Fired when an existing touch disappears
.. versionchanged:: 1.0.9
Everything related to event properties has been moved to
:class:`~kivy.event.EventDispatcher`. Event properties can now be used
in contructing a simple class, without subclassing :class:`Widget`.
.. versionchanged:: 1.5.0
Constructor now accept on_* arguments to automatically bind callbacks to
properties or events, as the Kv language.
'''
__metaclass__ = WidgetMetaclass
def __init__(self, **kwargs):
# Before doing anything, ensure the windows exist.
EventLoop.ensure_window()
# Register touch events
self.register_event_type('on_touch_down')
self.register_event_type('on_touch_move')
self.register_event_type('on_touch_up')
super(Widget, self).__init__(**kwargs)
# Create the default canvas if not exist
if self.canvas is None:
self.canvas = Canvas(opacity=self.opacity)
# Apply all the styles
if '__no_builder' not in kwargs:
#current_root = Builder.idmap.get('root')
#Builder.idmap['root'] = self
Builder.apply(self)
#if current_root is not None:
# Builder.idmap['root'] = current_root
#else:
# Builder.idmap.pop('root')
# Bind all the events
for argument in kwargs:
if argument[:3] == 'on_':
self.bind(**{argument: kwargs[argument]})
#
# Collision
#
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 window coordinates)
`y`: numeric
Y position of the point (in window coordinates)
:Returns:
bool, True if the point is inside the bounding box.
>>> Widget(pos=(10, 10), size=(50, 50)).collide_point(40, 40)
True
'''
return self.x <= x <= self.right and self.y <= y <= self.top
def collide_widget(self, wid):
'''Check if the other widget collides with this widget.
Performs an axis-aligned bounding box intersection test by default.
:Parameters:
`wid`: :class:`Widget` class
Widget to collide with.
:Returns:
bool, True if the other widget collides with this widget.
>>> 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
#
def on_touch_down(self, touch):
'''Receive a touch down event.
:Parameters:
`touch`: :class:`~kivy.input.motionevent.MotionEvent` class
Touch received
:Returns:
bool. If True, the dispatching of the touch will stop.
'''
for child in self.children[:]:
if child.dispatch('on_touch_down', touch):
return True
def on_touch_move(self, touch):
'''Receive a touch move event.
See :meth:`on_touch_down` for more information
'''
for child in self.children[:]:
if child.dispatch('on_touch_move', touch):
return True
def on_touch_up(self, touch):
'''Receive a touch up event.
See :meth:`on_touch_down` for more information
'''
for child in self.children[:]:
if child.dispatch('on_touch_up', touch):
return True
#
# Tree management
#
def add_widget(self, widget, index=0):
'''Add a new widget as a child of this widget.
:Parameters:
`widget`: :class:`Widget`
Widget to add to our list of children.
`index`: int, default to 0
*(this attribute have been added in 1.0.5)*
Index to insert the widget in the list
>>> root = Widget()
>>> root.add_widget(Button())
>>> slider = Slider()
>>> root.add_widget(slider)
'''
if widget is self:
raise WidgetException('You cannot add yourself in a Widget')
if not isinstance(widget, Widget):
raise WidgetException(
'add_widget() can be used only with Widget classes.')
parent = widget.parent
# check if 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 = self
if index == 0 or len(self.children) == 0:
self.children.insert(0, widget)
self.canvas.add(widget.canvas)
else:
canvas = self.canvas
children = self.children
if index >= len(children):
index = len(children)
next_index = -1
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)
canvas.insert(next_index, widget.canvas)
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.
>>> root = Widget()
>>> button = Button()
>>> root.add_widget(button)
>>> root.remove_widget(button)
'''
if widget not in self.children:
return
self.children.remove(widget)
self.canvas.remove(widget.canvas)
widget.parent = None
def clear_widgets(self):
'''Remove all widgets added to this widget.
'''
remove_widget = self.remove_widget
for child in self.children[:]:
remove_widget(child)
def get_root_window(self):
'''Return the root window.
:Returns:
Instance of the root window. Can be
:class:`~kivy.core.window.WindowBase` or
:class:`Widget`
'''
if self.parent:
return self.parent.get_root_window()
def get_parent_window(self):
'''Return the parent window.
:Returns:
Instance of the parent window. Can be
:class:`~kivy.core.window.WindowBase` or
:class:`Widget`
'''
if self.parent:
return self.parent.get_parent_window()
def to_widget(self, x, y, relative=False):
'''Convert the given coordinate from window to local widget
coordinates.
'''
if self.parent:
x, y = self.parent.to_widget(x, y)
return self.to_local(x, y, relative=relative)
def to_window(self, x, y, initial=True, relative=False):
'''Transform local coordinates to window coordinates.'''
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)
def to_parent(self, x, y, relative=False):
'''Transform local coordinates to parent coordinates.
:Parameters:
`relative`: bool, default to False
Change to True if you want to translate relative positions from
widget to its parent.
'''
if relative:
return (x + self.x, y + self.y)
return (x, y)
def to_local(self, x, y, relative=False):
'''Transform parent coordinates to local coordinates.
:Parameters:
`relative`: bool, default 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)
x = NumericProperty(0)
'''X position of the widget.
:data:`x` is a :class:`~kivy.properties.NumericProperty`, default to 0.
'''
y = NumericProperty(0)
'''Y position of the widget.
:data:`y` is a :class:`~kivy.properties.NumericProperty`, default to 0.
'''
width = NumericProperty(100)
'''Width of the widget.
:data:`width` is a :class:`~kivy.properties.NumericProperty`, default
to 100.
'''
height = NumericProperty(100)
'''Height of the widget.
:data:`height` is a :class:`~kivy.properties.NumericProperty`, default
to 100.
'''
pos = ReferenceListProperty(x, y)
'''Position of the widget.
:data:`pos` is a :class:`~kivy.properties.ReferenceListProperty` of
(:data:`x`, :data:`y`) properties.
'''
size = ReferenceListProperty(width, height)
'''Size of the widget.
:data:`size` is a :class:`~kivy.properties.ReferenceListProperty` of
(:data:`width`, :data:`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'))
'''Right position of the widget.
:data:`right` is a :class:`~kivy.properties.AliasProperty` of
(:data:`x` + :data:`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'))
'''Top position of the widget.
:data:`top` is a :class:`~kivy.properties.AliasProperty` of
(:data:`y` + :data:`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'))
'''X center position of the widget.
:data:`center_x` is a :class:`~kivy.properties.AliasProperty` of
(:data:`x` + :data:`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'))
'''Y center position of the widget.
:data:`center_y` is a :class:`~kivy.properties.AliasProperty` of
(:data:`y` + :data:`height` / 2.)
'''
center = ReferenceListProperty(center_x, center_y)
'''Center position of the widget.
:data:`center` is a :class:`~kivy.properties.ReferenceListProperty` of
(:data:`center_x`, :data:`center_y`)
'''
cls = ListProperty([])
'''Class of the widget, used for styling.
'''
id = StringProperty(None, allownone=True)
'''Unique identifier of the widget in the tree.
:data:`id` is a :class:`~kivy.properties.StringProperty`, default to None.
.. warning::
If the :data:`id` is already used in the tree, an exception will
be raised.
'''
children = ListProperty([])
'''List of children of this widget.
:data:`children` is a :class:`~kivy.properties.ListProperty` instance,
default to an empty list.
Use :meth:`add_widget` and :meth:`remove_widget` for manipulating the
children list. Don't manipulate the children list directly until you know
what you are doing.
'''
parent = ObjectProperty(None, allownone=True)
'''Parent of this widget.
:data:`parent` is a :class:`~kivy.properties.ObjectProperty` instance,
default to None.
The parent of a widget is set when the widget is added to another one, and
unset when the widget is removed from its parent.
'''
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 :class:`~kivy.uix.layout.Layout` and
:class:`~kivy.core.window.Window` make use of the hint.
The value is in percent as a float from 0. to 1., where 1. means the full
size of his parent. 0.5 represents 50%.
:data:`size_hint_x` is a :class:`~kivy.properties.NumericProperty`, default
to 1.
'''
size_hint_y = NumericProperty(1, allownone=True)
'''Y size hint.
:data:`size_hint_y` is a :class:`~kivy.properties.NumericProperty`, default
to 1.
See :data:`size_hint_x` for more information
'''
size_hint = ReferenceListProperty(size_hint_x, size_hint_y)
'''Size hint.
:data:`size_hint` is a :class:`~kivy.properties.ReferenceListProperty` of
(:data:`size_hint_x`, :data:`size_hint_y`)
See :data:`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', 'center_x', will use the parent width.
The keys 'y', 'top', 'center_y', will use the parent height.
See :doc:`api-kivy.uix.floatlayout` for further reference.
Position hint is only used in :class:`~kivy.uix.floatlayout.FloatLayout` and
:class:`~kivy.core.window.Window`.
:data:`pos_hint` is a :class:`~kivy.properties.ObjectProperty` containing a
dict.
'''
ids = DictProperty({})
'''This is a Dictionary of id's defined in your kv language. This will only
be populated if you use id's in your kv language code.
.. versionadded:: 1.6.0
:data:`ids` is a :class:`~kivy.properties.DictProperty`, defaults to a empty
dict {}.
'''
opacity = NumericProperty(1.0)
'''Opacity of the widget and all the 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 to the
current global opacity, and the result is applied to the current context
color.
For example: if your parent have an opacity of 0.5, and one children have an
opacity of 0.2, the real opacity of the children will be 0.5 * 0.2 = 0.1.
Then, the opacity is applied on the shader as::
frag_color = color * vec4(1.0, 1.0, 1.0, opacity);
:data:`opacity` is a :class:`~kivy.properties.NumericProperty`, default 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.
'''