Table Of Contents

• Migrating from Kivy 2.x.x to Kivy 3.x.x
  • Introduction
  • Renamed modules and environment variables
  • Removals
    • ButtonBehavior
    • ToggleButtonBehavior
    • Clock
    • AliasProperty
    • Mouse Input Provider
    • SVG
• Application Storage Directories

Migrating from Kivy 2.x.x to Kivy 3.x.x

Introduction

Kivy 3.x.x introduces several changes and improvements compared to Kivy 2.x.x. This guide will help you migrate your existing Kivy 2.x.x codebase to Kivy 3.x.x.

Renamed modules and environment variables

Migration from kivy.core.audio to kivy.core.audio_output

In Kivy 3.x.x, the kivy.core.audio module has been renamed as kivy.core.audio_output.

Import Statement Changes

To migrate your code, you need to update the import statements in your codebase. For example, if you have the following import statement in your code:

from kivy.core.audio import SoundLoader

You need to update it to:

from kivy.core.audio_output import SoundLoader

Environment Variable Changes

The environment variable has also been renamed from KIVY_AUDIO to KIVY_AUDIO_OUTPUT.

If you were using the KIVY_AUDIO environment variable to specify audio provider preferences, you need to update it to KIVY_AUDIO_OUTPUT. For example:

in Python before importing Kivy:

import os

# Kivy 2.x.x
os.environ['KIVY_AUDIO'] = 'sdl3,gstplayer'
import kivy

# Kivy 3.x.x
os.environ['KIVY_AUDIO_OUTPUT'] = 'sdl3,gstplayer'
import kivy

Removals

Removal of `.play` property from `kivy.uix.video.Video` and `kivy.uix.videoplayer.VideoPlayer`

In Kivy 3.x.x, the .play property has been removed from the kivy.uix.video.Video and kivy.uix.videoplayer.VideoPlayer classes.

To migrate your code, you need to update the references to the .play property in your codebase. For example, if you have the following code in your Kivy 2.x.x codebase:

video = Video(source='video.mp4')

# Play the video
video.play = True

# Stop the video
video.play = False

You need to update it to:

video = Video(source='video.mp4')

# Play the video
video.state = 'play'

# Stop the video
video.state = 'stop'

# Pause the video
video.state = 'pause'

Removal of `padding_x` and `padding_y` Properties from `kivy.uix.textinput.TextInput`

In Kivy 3.x.x the padding_x and padding_y properties have been removed from the kivy.uix.textinput.TextInput class. Instead, padding is now managed through the unified padding property.

To update your code, replace instances of padding_x and padding_y with the padding property.

The padding property accepts a list of values, allowing for more flexible padding configurations:

• [horizontal, vertical] — e.g., [10, 10]

• [padding_left, padding_top, padding_right, padding_bottom] — e.g., [10, 5, 10, 5]

For more details on how to use the padding property, please refer to the related documentation.

Removal of `file_encodings` Property from `kivy.uix.filechooser.FileChooserController`

In Kivy 3.x.x, the file_encodings property has been removed from the kivy.uix.filechooser.FileChooserController class.

The file_encodings property was deprecated and it was kept for backward compatibility, however it was just ignored and not used internally.

To migrate your code, you just need to remove any references to the file_encodings property in your codebase.

Removal of deprecated `on_dropfile` Window event name

In Kivy 3.x.x, the previously deprecated on_dropfile event name has been removed. Use on_drop_file instead.

The event was renamed in Kivy 2.1.0, so any remaining compatibility code that still binds to on_dropfile now needs to be updated.

# Kivy 2.x.x (legacy/deprecated name)
from kivy.core.window import Window

def handle_drop(window, filename):
    print(filename)

Window.bind(on_dropfile=handle_drop)

# Kivy 3.x.x
from kivy.core.window import Window

def handle_drop(window, filename, x, y, *args):
    print(filename, x, y)

Window.bind(on_drop_file=handle_drop)

If you dispatch or override the event directly, also rename any on_dropfile method implementations to on_drop_file.

Removal of the Kv-lang Templates feature

In Kivy 3.x.x, the deprecated Kivy language Templates feature (introduced in 1.0.5, deprecated in 1.7.0) has been removed. The following are gone:

• The [Name@Base]: Kv-lang template syntax (any kv file that contains a [...]: selector will now raise a ParserException at load time).

• Builder.template(name, **ctx) and the Builder.templates dict.

• Factory.is_template() and the is_template= keyword argument of Factory.register().

Migrate to dynamic classes (<Name@Base>:). Dynamic classes have largely superseded templates since Kivy 1.7.0 and support normal Kivy properties, binding and inheritance.

Migrating a template in `.kv`

# Kivy 2.x.x
[IconItem@BoxLayout]:
    Image:
        source: ctx.image
    Label:
        text: ctx.title

# Kivy 3.x.x
<IconItem@BoxLayout>:
    image: ''
    title: ''
    Image:
        source: root.image
    Label:
        text: root.title

Note the two changes: [...]: becomes <...>:, and ctx.foo references become root.foo references against properties declared on the rule itself.

Migrating `Builder.template(…)` instantiation

# Kivy 2.x.x
from kivy.lang import Builder
icon = Builder.template('IconItem', title='Hello', image='myimage.png')

# Kivy 3.x.x
from kivy.factory import Factory
icon = Factory.IconItem()
icon.title = 'Hello'
icon.image = 'myimage.png'

Because dynamic-class properties are added to the widget by the rule (rather than declared on the class), they are not yet present when __init__ processes its kwargs - so pass values via setattr (or property assignment) after construction rather than as constructor kwargs. If you need constructor-kwarg support, define the widget as a regular Python class with explicit Property declarations instead.

AccordionItem: `title_template` and `title_args` replaced by `title_class`

The AccordionItem widget previously used the Kv-lang templates feature to render its title bar via the title_template (string) and title_args (dict) properties. Both properties have been removed.

The replacement is title_class. It accepts either a class object or a Factory-resolvable string. The class is instantiated with two keyword arguments: title and item.

To customise the appearance of the title widget, subclass AccordionItemTitle (or write any widget that accepts title and item kwargs) and pass it via title_class.

See also

title_class documentation.

ButtonBehavior

Removal of `state`, `min_state_time`, `last_touch` Properties and `trigger_action()` Method

In Kivy 3.x.x, the ButtonBehavior class has been significantly simplified and improved. The state OptionProperty, min_state_time NumericProperty, and last_touch ObjectProperty have been removed, along with the trigger_action() method. A simpler, read-only pressed BooleanProperty is now used to indicate the button’s state.

Event Signature Changes

The on_press, on_release, and on_cancel (new event) events now receive a touch argument containing the MotionEvent that triggered the event:

# Kivy 2.x.x
class MyButton(ButtonBehavior, Label):
    def on_press(self):
        print("Button pressed")

    def on_release(self):
        print("Button released")

# Kivy 3.x.x
class MyButton(ButtonBehavior, Label):
    def on_press(self, touch):
        print(f"Button pressed at {touch.pos}")

    def on_release(self, touch):
        print(f"Button released at {touch.pos}")

    def on_cancel(self, touch):  # NEW event
        print(f"Button cancelled at {touch.pos}")

When binding to these events, the callback receives both the widget instance and the touch:

# Kivy 2.x.x
def on_press_callback(instance):
    print(f"{instance} was pressed")

button.bind(on_press=on_press_callback)

# Kivy 3.x.x
def on_press_callback(instance, touch):
    print(f"{instance} was pressed at {touch.pos}")

button.bind(on_press=on_press_callback)

class MyButton(ButtonBehavior, Label):
    def on_press(self, touch):
        # Store press time for duration calculation
        self.press_time = touch.time_start

    def on_release(self, touch):
        # Calculate how long the button was pressed
        duration = touch.time_end - self.press_time
        print(f"Button pressed for {duration:.2f} seconds")

        # Access touch position
        print(f"Released at ({touch.x}, {touch.y})")

Multi-Touch Touch Argument Behavior

In multi-touch scenarios:

• on_press: Receives the first touch that triggered the press

• on_release: Receives the last touch being released

• on_cancel: Receives the last touch that moved outside bounds

class MyButton(ButtonBehavior, Label):
    def on_press(self, touch):
        # This is the first touch
        print(f"First touch ID: {touch.id}")

    def on_release(self, touch):
        # This is the last touch being released
        print(f"Last touch ID: {touch.id}")

Migrating from `state` to `pressed`

The state property that could be ‘normal’ or ‘down’ has been replaced with a boolean pressed property. Note that pressed is read-only (an AliasProperty), unlike the old state which could be set directly.

# Kivy 2.x.x
if button.state == 'down':
    print("Button is pressed")

button.state = 'down'  # Could set state directly

# Kivy 3.x.x
if button.pressed:
    print("Button is pressed")

# button.pressed = True  # NOT ALLOWED - read-only property

In KV language:

# Kivy 2.x.x
Button:
    color: (1, 0, 0, 1) if self.state == 'down' else (1, 1, 1, 1)

# Kivy 3.x.x
Button:
    color: (1, 0, 0, 1) if self.pressed else (1, 1, 1, 1)

Binding to State Changes

Use the on_pressed property event instead of on_state:

# Kivy 2.x.x
def on_state(self, instance, value):
    if value == 'down':
        print("Pressed")
    else:
        print("Released")

# Kivy 3.x.x
def on_pressed(self, instance, is_pressed):
    if is_pressed:
        print("Pressed")
    else:
        print("Released")

Migrating from `min_state_time`

The min_state_time property, which enforced a minimum duration for the ‘down’ state, has been removed. If you need similar behavior, you can implement it manually using Clock.create_trigger():

from kivy.clock import Clock
from kivy.uix.behaviors import ButtonBehavior
from kivy.uix.label import Label

class DelayedButton(ButtonBehavior, Label):
    MIN_STATE_TIME = 0.5  # seconds

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self._release_trigger = Clock.create_trigger(
            self._delayed_action,
            self.MIN_STATE_TIME
        )
        self.bind(pressed=self._pressed_changed)

    def _pressed_changed(self, instance, is_pressed):
        if is_pressed:
            self._release_trigger.cancel()
        else:
            self._release_trigger()  # schedule delayed action

    def _delayed_action(self, dt):
        # Your delayed logic here
        print("Action executed after minimum time")

Removal of `trigger_action()` Method

The trigger_action() method has been removed. This method was used to programmatically simulate button presses, but it violated the principle of UI event simulation and wasn’t properly integrated with the touch system.

# Kivy 2.x.x
button.trigger_action(duration=0.1)

If you need to programmatically trigger button actions in Kivy 3.x.x, you have two options:

Option 1: Dispatch events directly (recommended for simple cases)

Simply dispatch the on_press and on_release events. You’ll need to provide a touch-like object:

# Kivy 3.x.x - Direct event dispatch
# Create a simple object with touch attributes
class TouchProxy:
    def __init__(self, pos):
        self.pos = pos
        self.x, self.y = pos
        self.id = 0
        self.time_start = 0
        self.time_end = 0
        self.ud = {}

touch = TouchProxy(button.center)
button.dispatch('on_press', touch)
# ... your logic ...
button.dispatch('on_release', touch)

Note that this approach does NOT update the pressed property or trigger internal state changes, as those are tied to actual touch events.

Option 2: Simulate touch events (for complete button state simulation)

If you need the button to fully simulate touch behavior (including updating the pressed property), you must simulate actual touch events:

from kivy.input.motionevent import MotionEvent
from kivy.clock import Clock

class MyButton(ButtonBehavior, Label):
    def simulate_press(self, duration=0.1):
        """Simulate a complete button press with touch events."""
        # Create a mock touch event
        touch = MotionEvent('mock', 0, {
            'x': self.center_x,
            'y': self.center_y,
            'pos': (self.center_x, self.center_y)
        })

        # Simulate touch down
        self.on_touch_down(touch)

        # Simulate touch up after duration
        def release_touch(dt):
            self.on_touch_up(touch)

        if duration > 0:
            Clock.schedule_once(release_touch, duration)
        else:
            release_touch(0)

Or create a helper method in your custom button class:

from kivy.clock import Clock
from kivy.uix.behaviors import ButtonBehavior
from kivy.uix.label import Label

class TouchProxy:
    """Simple object that mimics touch attributes."""
    def __init__(self, pos):
        self.pos = pos
        self.x, self.y = pos
        self.id = 0
        self.time_start = 0
        self.time_end = 0
        self.ud = {}

class MyButton(ButtonBehavior, Label):
    def trigger_action(self, duration=0.1):
        """Simulate button press/release."""
        # Create touch proxy
        touch = TouchProxy(self.center)

        self._do_press(touch)
        self.dispatch('on_press', touch)

        def trigger_release(dt):
            self._do_release(touch)
            self.dispatch('on_release', touch)

        if not duration:
            trigger_release(0)
        else:
            Clock.schedule_once(trigger_release, duration)

Removal of `last_touch` Property

The last_touch ObjectProperty has been removed. However, since events now receive the touch as an argument, you can easily track it if needed:

# Kivy 2.x.x
class MyButton(ButtonBehavior, Label):
    def on_press(self):
        print(f"Touch at: {self.last_touch.pos}")

# Kivy 3.x.x - Option 1: Use touch argument directly
class MyButton(ButtonBehavior, Label):
    def on_press(self, touch):
        print(f"Touch at: {touch.pos}")

# Kivy 3.x.x - Option 2: Track manually if needed elsewhere
class MyButton(ButtonBehavior, Label):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.last_touch = None

    def on_press(self, touch):
        self.last_touch = touch
        print(f"Touch at: {touch.pos}")

Improved Multi-Touch Behavior

The on_release event behavior has changed for multi-touch scenarios:

• Kivy 2.x.x: on_release fires when the first touch is released (even if other touches are still active)

• Kivy 3.x.x: on_release fires only after all active touches are released

# Example: Multi-touch behavior difference
class MyButton(ButtonBehavior, Label):
    def on_release(self, touch):
        print(f"Button released - last touch ID: {touch.id}")

# Scenario: User presses button with 3 fingers, then lifts them one by one
# Kivy 2.x.x: "Button released" prints when the FIRST finger is lifted
# Kivy 3.x.x: "Button released" prints only when ALL 3 fingers are lifted

If you need the old behavior (release on first touch up), override on_touch_up:

class LegacyButton(ButtonBehavior, Label):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self._first_touch_released = False

    def on_touch_down(self, touch):
        result = super().on_touch_down(touch)
        if result:
            self._first_touch_released = False
        return result

    def on_touch_up(self, touch):
        if touch.grab_current is self and not self._first_touch_released:
            self._first_touch_released = True
            self._do_release(touch)
            self.dispatch('on_release', touch)
        return super().on_touch_up(touch)

New `on_cancel` Event

A new event on_cancel is now dispatched when a touch moves outside the button bounds during a drag operation. This only occurs when always_release=False (the default).

class MyButton(ButtonBehavior, Label):
    def on_press(self, touch):
        self.color = (1, 0, 0, 1)  # Red when pressed
        print(f"Pressed at {touch.pos}")

    def on_release(self, touch):
        self.color = (0, 1, 0, 1)  # Green on successful release
        print(f"Released at {touch.pos}")
        print("Button action executed")

    def on_cancel(self, touch):
        self.color = (1, 1, 1, 1)  # White when cancelled
        print(f"Cancelled at {touch.pos}")
        print("Button action cancelled")

This event allows you to provide visual feedback when the user drags their finger/pointer outside the button, indicating the action will not be executed.

Changed `always_release` Behavior

The behavior when always_release=False (default) has been improved:

Kivy 2.x.x: When touch moved outside bounds, on_release didn’t fire. However, if the user moved the touch back inside the button bounds before releasing, on_release would fire normally. This could cause unexpected side effects.

Kivy 3.x.x: When touch moves outside bounds during drag: - on_cancel event fires immediately (NEW) - Touch is marked as cancelled permanently - on_release will NOT fire, even if touch moves back inside before release - Provides explicit feedback about cancellation - Now, canceled on_release are explicitly canceled on_release`(`on_cancel).

# Example: Standard button behavior (always_release=False)
class StandardButton(ButtonBehavior, Label):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.always_release = False  # Default, but explicit here

    def on_press(self, touch):
        print("Action started")
        self.text = "Release here to confirm"

    def on_release(self, touch):
        print("Action confirmed!")
        self.text = "Confirmed"

    def on_cancel(self, touch):
        print("Action cancelled")
        self.text = "Cancelled - press again"

When always_release=True, the behavior remains the same - on_release always fires and on_cancel never fires:

# Example: Always release (drag-and-drop style)
class DragButton(ButtonBehavior, Label):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.always_release = True  # Release fires anywhere

    def on_release(self, touch):
        print(f"Released at {touch.pos} - on_cancel never fires")

Internal Hooks for Subclassing

The methods _do_press(), _do_release(), and _do_cancel() are now documented as internal hooks for subclasses (like ToggleButtonBehavior). These are called before the corresponding public events are dispatched and now also receive the touch argument.

Note

Avoid using these methods, they are for internal state management in subclasses. Application code should use the on_press, on_release, and on_cancel events instead.

class CustomButton(ButtonBehavior, Label):
    def _do_press(self, touch):
        # Internal state changes before event dispatch (for internal use only)
        super()._do_press(touch)
        self._internal_state = "pressing"
        self._press_position = touch.pos

    def on_press(self, touch):
        # Public event handler for application logic
        print(f"Button pressed at {touch.pos} - use this for your logic")

Summary of Breaking Changes

Removed/Changed	Kivy 2.x.x	Kivy 3.x.x
state property	‘normal’ or ‘down’	Removed - use pressed (read-only)
min_state_time	NumericProperty (0.035)	Removed - implement manually
last_touch	ObjectProperty	Removed - events receive touch arg
trigger_action()	Method available	Removed - dispatch events with mock
Event signatures	on_press() on_release()	on_press(touch) - touch argument added on_release(touch)
on_release behavior	Fires on first touch up	Fires after all touches released
on_cancel event	Not available	New - on_cancel(touch) fires on drag outside bounds
always_release=False	Silent non-release	Explicit on_cancel event with touch
Internal hooks	Undocumented	Documented _do_*(touch) methods

ToggleButtonBehavior

Replacement of `state` with `activated` and Major API Improvements

In Kivy 3.x.x, ToggleButtonBehavior has undergone significant improvements and changes. The most notable change is replacing the state OptionProperty with an activated boolean property (AliasProperty), along with new features like scoped groups and the toggle_on property.

Migrating from `state` to `activated`

The state property (‘normal’ or ‘down’) has been replaced with a boolean activated property:

# Kivy 2.x.x
if toggle.state == 'down':
    print("Toggle is active")
    toggle.state = 'normal'  # Deactivate

# Kivy 3.x.x
if toggle.activated:
    print("Toggle is active")
    toggle.activated = False  # Deactivate

In KV language:

# Kivy 2.x.x
ToggleButton:
    text: "ON" if self.state == 'down' else "OFF"
    color: (0, 1, 0, 1) if self.state == 'down' else (1, 1, 1, 1)

# Kivy 3.x.x
ToggleButton:
    text: "ON" if self.activated else "OFF"
    color: (0, 1, 0, 1) if self.activated else (1, 1, 1, 1)

New `on_activated` Event

Replace on_state bindings with on_activated:

# Kivy 2.x.x
class MyToggle(ToggleButtonBehavior, Label):
    def on_state(self, instance, value):
        if value == 'down':
            print("Activated")
            self.background_color = (0, 1, 0, 1)
        else:
            print("Deactivated")
            self.background_color = (1, 1, 1, 1)

# Kivy 3.x.x
class MyToggle(ToggleButtonBehavior, Label):
    def on_activated(self, instance, value):
        if value:
            print("Activated")
            self.color = (0, 1, 0, 1)
        else:
            print("Deactivated")
            self.color = (1, 1, 1, 1)

In KV language, bind to property changes:

# Kivy 2.x.x
<MyToggle@ToggleButton>:
    on_state: app.handle_toggle(self, self.state)

# Kivy 3.x.x
<MyToggle@ToggleButton>:
    on_activated: app.handle_toggle(self, self.activated)

New `toggle_on` Property

A new toggle_on property controls when the toggle state changes - either on press or on release (default):

# Kivy 3.x.x - Toggle immediately on press
ToggleButton:
    toggle_on: 'press'

# Kivy 3.x.x - Toggle on release (default)
ToggleButton:
    toggle_on: 'release'

This is useful when you want instant visual feedback:

from kivy.uix.behaviors import ToggleButtonBehavior
from kivy.uix.label import Label

class InstantToggle(ToggleButtonBehavior, Label):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.toggle_on = 'press'  # Toggle immediately

    def on_activated(self, instance, value):
        self.text = "ON" if value else "OFF"

Scoped Groups (New Tuple Syntax)

Groups can now be scoped to specific widget owners using tuple syntax. This prevents conflicts when creating reusable components:

# Kivy 2.x.x - Only global groups (string)
ToggleButton:
    group: 'options'  # Global across entire application

# Kivy 3.x.x - Global groups (still supported)
ToggleButton:
    group: 'options'

# Kivy 3.x.x - Scoped groups (NEW)
ToggleButton:
    group: (root, 'options')  # Scoped to 'root' widget

Scoped Group Format: (owner, name)

• owner: Any object to scope the group to (typically a widget)

• name: Hashable identifier (string, int, enum, etc.)

Example of reusable component with scoped groups:

from kivy.uix.boxlayout import BoxLayout
from kivy.uix.togglebutton import ToggleButton

class FilterPanel(BoxLayout):
    """Reusable panel with independent toggle groups."""

    def __init__(self, **kwargs):
        super().__init__(**kwargs)

        # Each FilterPanel instance has its own "size" group
        for size in ["Small", "Medium", "Large"]:
            btn = ToggleButton(
                text=size,
                group=(self, "size"),  # Scoped to this FilterPanel instance
                allow_no_selection=False
            )
            self.add_widget(btn)

# Multiple panels won't interfere with each other
panel1 = FilterPanel()  # Has independent "size" group
panel2 = FilterPanel()  # Has independent "size" group

In KV language:

<FilterPanel@BoxLayout>:
    ToggleButton:
        text: "Small"
        group: (root, "size")  # Scoped to FilterPanel instance
    ToggleButton:
        text: "Medium"
        group: (root, "size")
    ToggleButton:
        text: "Large"
        group: (root, "size")

# Each instance has independent groups
BoxLayout:
    FilterPanel:  # Independent "size" group
    FilterPanel:  # Independent "size" group

When to Use Scoped vs Global Groups

Use global groups (string) when: - You want all toggles across the app to share the same group - Building simple single-instance interfaces

Use scoped groups (tuple) when: - Creating reusable components with internal toggle groups - Multiple instances of the same component shouldn’t interfere - Building complex layouts with nested toggle groups

Method Changes: `get_widgets()` → `get_group()`

The static method get_widgets(groupname) has been replaced with an instance method get_group():

# Kivy 2.x.x - Static method
widgets = ToggleButtonBehavior.get_widgets('mygroup')
for widget in widgets:
    print(widget.text)
del widgets  # Always delete to prevent memory leaks

# Kivy 3.x.x - Instance method
widgets = my_toggle_button.get_group()
for widget in widgets:
    print(widget.text)
del widgets  # Still recommended to delete to prevent memory leaks

The new get_group() method: - Returns widgets in the same group as the calling instance - Works with both global and scoped groups automatically - Includes the calling widget in the returned list

# Example usage
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.togglebutton import ToggleButton

class MyApp(App):
    def build(self):
        layout = BoxLayout()

        btn1 = ToggleButton(text="Option 1", group="options")
        btn2 = ToggleButton(text="Option 2", group="options")
        btn3 = ToggleButton(text="Option 3", group="options")

        layout.add_widget(btn1)
        layout.add_widget(btn2)
        layout.add_widget(btn3)

        # Get all widgets in btn1's group
        group_widgets = btn1.get_group()
        print(f"Group has {len(group_widgets)} widgets")  # Prints: 3
        del group_widgets

        return layout

Removal of `_clear_groups()` and `_release_group()`

The static method _clear_groups() and instance method _release_group() have been removed. Group management is now handled automatically through weak references.

# Kivy 2.x.x - Manual group management
class MyToggle(ToggleButtonBehavior, Label):
    def custom_release(self):
        self._release_group(self)
        self.state = 'normal'

# Kivy 3.x.x - Automatic group management
class MyToggle(ToggleButtonBehavior, Label):
    def custom_release(self):
        self.activated = False  # Automatically manages group

Improved Group Cleanup

Group management now uses WeakSet for automatic cleanup when widgets are deleted. You no longer need to manually clean up groups:

# Kivy 2.x.x - Potential memory leaks if not careful
toggle = ToggleButton(group='mygroup')
del toggle  # Weak reference might linger

# Kivy 3.x.x - Automatic cleanup
toggle = ToggleButton(group='mygroup')
del toggle  # Automatically removed from group via WeakSet

Summary of Breaking Changes

Clock

Improved @triggered Decorator Behavior, Instance Isolation and Debouncing

In Kivy 3.x.x, the triggered() decorator has been significantly improved. Previously, when used as a method decorator, it shared a single trigger and state across all instances of a class. This meant that calling the method on one instance would throttle calls on all other instances, and arguments from different instances could overwrite each other.

Behavior Changes

• Improved Instance Isolation: Each instance now has its own isolated trigger and argument storage. Calling a triggered method on widget_a no longer affects widget_b.

• Improved Lazy Initialization: Triggers are now created only when the decorated function is first called, improving initialization performance.

• New is_triggered Property: A new is_triggered property was added to the decorated function/method, allowing you to check if a call is currently pending.

• New debounce Parameter: A new debounce=False (default) parameter was added.

  • Throttling (default): Subsequent calls while a trigger is active update the arguments but do not reset the timer. The function fires once after the initial timeout.

  • Debouncing (debounce=True): Subsequent calls cancel any pending execution and reschedule it. The function only fires after the caller stops calling it for the duration of the timeout.

Migration Impact

This is primarily a bug fix and a set of new features. It should not require code changes for most applications. However, if your codebase intentionally relied on the legacy shared throttling behavior across different instances, you can restore this behavior by using the ``@classmethod`` decorator above @triggered.

This ensures the trigger is bound to the class object rather than individual instances, restoring the shared behavior in an idiomatic way.

class MyWidget(Widget):
    # Default in 3.x.x: Isolated per instance
    @triggered(0.1)
    def sync_ui(self, *args):
        pass

    # Shared behavior (same as legacy 2.x.x): Shared by all instances
    @classmethod
    @triggered(0.1)
    def sync_shared_data(cls, *args):
        pass

    # Optional: Debouncing (0.1s from the LAST call)
    @triggered(0.1, debounce=True)
    def search_input(self, text):
        pass

AliasProperty

Fixed Dispatch Inconsistencies for the Initial Value and None Getter Results

In Kivy 3.x.x, two related bugs in AliasProperty dispatch have been fixed (see #6901).

Behavior Changes

• Initial value is now always dispatched. Previously, whether the very first value of an AliasProperty was dispatched (e.g. when one of its bind-ed dependencies changed before the alias property had ever been read) depended on unrelated implementation details, such as whether the alias property had already been read once, or whether an on_<name> handler existed on the class (which forced an early read during __init__). Now, the first time an alias property’s value is established, it is always dispatched exactly once.

• Fixed missed dispatches when the getter returns None. Previously, the alias property’s internally tracked value was only kept up to date when cache=True. This meant that with cache=False, real changes could be silently missed (or, if the getter’s result happened to equal a leftover default, dropped) whenever the getter legitimately returned None. The internal tracking is now always kept in sync, regardless of cache, so changes are correctly detected and dispatched even when the getter returns None.

from kivy.event import EventDispatcher
from kivy.properties import NumericProperty, AliasProperty

class Rect(EventDispatcher):
    width = NumericProperty(0)
    height = NumericProperty(0)

    def _get_aspect_ratio(self):
        return (self.width / self.height) if self.height else None

    aspect_ratio = AliasProperty(
        _get_aspect_ratio, None, bind=('width', 'height'), cache=True)

    def on_aspect_ratio(self, instance, value):
        print(f'aspect_ratio: {value}')

# Kivy 2.x.x
r = Rect(width=100)
r.height = 1   # prints "aspect_ratio: 100.0"
r.height = 0   # missing dispatch - `on_aspect_ratio` is NOT called

# Kivy 3.x.x
r = Rect(width=100)
r.height = 1   # prints "aspect_ratio: 100.0"
r.height = 0   # prints "aspect_ratio: None"

Migration Impact

This is primarily a bug fix. It should not require code changes for most applications, and in most cases will surface events (dispatches) that your application was previously and incorrectly not receiving.

The one behavior to be aware of: code that binds to an AliasProperty (directly, via bind()/fbind(), or implicitly via an on_<name> handler) and relies on its dependencies changing during __init__ may now observe an extra initial dispatch call that previously did not fire in some constructions. If your callback assumed it would only ever be called for genuine value transitions, guard against redundant no-op work as needed, for example by comparing against the previously known value inside the callback itself.

Mouse Input Provider

Multiple Mouse Buttons Can Now Be Held Down Simultaneously

In Kivy 3.x.x, the mouse input provider (MouseMotionEventProvider) has been fixed to correctly track multiple mouse buttons that are held down at the same time when multitouch simulation is disabled (disable_multitouch) (see #3597).

Behavior Changes

• Multiple simultaneous button-drags are now tracked independently. Previously, the provider only tracked a single “current drag” at a time. If a second mouse button was pressed while a first button was still held down, the second button’s press was silently ignored (no on_touch_down was dispatched for it) until the first button was released. Now, each button gets its own independent touch when disable_multitouch is set, so pressing a second (or third) button while another is held correctly dispatches its own on_touch_down/on_touch_move/on_touch_up sequence.

• This change only affects behavior when disable_multitouch is active. When multitouch simulation is enabled (the default), only one simulated touch (the red dot) is tracked at a time, as before.

from kivy.app import App
from kivy.uix.widget import Widget


class MainWindow(Widget):
    def on_touch_down(self, touch):
        print(f'{touch.button} is being pressed')


class TestingApp(App):
    def build(self):
        return MainWindow()


if __name__ == '__main__':
    TestingApp().run()

# config: [input] mouse = mouse,disable_multitouch

# Kivy 2.x.x
# press and hold left -> "left is being pressed"
# press right while left is still held -> (nothing printed)

# Kivy 3.x.x
# press and hold left -> "left is being pressed"
# press right while left is still held -> "right is being pressed"

Migration Impact

This is primarily a bug fix. It should not require code changes for most applications, and mainly benefits applications using disable_multitouch that need to respond to more than one mouse button at a time (e.g. left + right held together).

SVG

Removal of the experimental kivy.graphics.svg module

In Kivy 3.x.x, the experimental Svg canvas instruction in kivy.graphics.svg has been removed, along with its example scripts under examples/svg/ (benchmark.py, main.py, main-smaa.py) and its Factory registration. The module had been marked experimental since its introduction and is superseded by the new SVG support added in Kivy 3.x.x.

Replacement: SvgWidget / AsyncSvgWidget

For most use cases, drop in SvgWidget (local sources) or AsyncSvgWidget (network sources):

# Kivy 2.x.x
from kivy.graphics.svg import Svg

with widget.canvas:
    Svg('image.svg')

# Kivy 3.x.x
from kivy.uix.svg import SvgWidget

widget.add_widget(SvgWidget(source='image.svg'))

In KV language:

# Kivy 3.x.x
SvgWidget:
    source: 'image.svg'

Replacement: kivy.core.svg image provider

For loading SVGs through the standard image pipeline (for example as a texture for Image), the new kivy.core.svg provider is selected automatically when an .svg source is loaded; no explicit import or Factory registration is required.

Factory registration

The Svg Factory entry that pointed at kivy.graphics.svg has been removed. SvgWidget and AsyncSvgWidget are registered in the Factory under their own names and can be used directly from KV.

Application Storage Directories

Linux user_data_dir Path Change (XDG Compliance Fix)

In Kivy 3.x.x, the App.user_data_dir path on Linux has been corrected to follow the XDG Base Directory specification. Previously, it incorrectly used XDG_CONFIG_HOME (for configuration files); it now correctly uses XDG_DATA_HOME (for application data).

Path Changes on Linux:

Property	Kivy 2.x.x	Kivy 3.x.x
user_data_dir	~/.config/<app_name> (incorrect)	~/.local/share/<app_name> (XDG-compliant)

Impact:

If your Linux application uses App.user_data_dir to store user data, the data will now be stored in a different location after upgrading to Kivy 3.x.x. This is the correct XDG-compliant location, but existing apps may need to migrate their data.

Migration Options:

1. Manual Migration (Recommended for production apps)

   Move existing data from the old location to the new location during app startup:

Note: Windows, macOS, iOS, and Android paths are unchanged.

New App.user_cache_dir Property

Kivy 3.x.x introduces a new App.user_cache_dir property for temporary/cache data that the system may delete at any time.

This is not a breaking change - it’s a new optional property. Existing apps continue to work unchanged.

Platform Paths:

• Windows: %APPDATA%\<app_name>\Cache

• macOS: ~/Library/Caches/<app_name>

• Linux: ~/.cache/<app_name> (respects $XDG_CACHE_HOME)

• Android: Context.getCacheDir()

• iOS: ~/Library/Caches/<app_name>

New KIVY_DESKTOP_PATH_ID Environment Variable

Kivy 3.x.x introduces KIVY_DESKTOP_PATH_ID to set user-friendly application directory names on desktop platforms.

This is not a breaking change - it’s opt-in. Existing apps continue to work unchanged unless you explicitly set this environment variable.

Key Feature:

Setting KIVY_DESKTOP_PATH_ID creates an application-specific location for the .kivy directory containing the config and log files. Without KIVY_DESKTOP_PATH_ID, the config and logs are placed in a single global .kivy directory (~/.kivy).

This means multiple Kivy applications can now have their own isolated configuration and log directories, preventing conflicts between different applications.

When Set:

The variable provides a human-readable application title for directories, making it easier for end users to identify your app’s directories when browsing their filesystem.

Example:

import os
os.environ['KIVY_DESKTOP_PATH_ID'] = 'My Photo Editor'

from kivy.app import App

# On Windows, creates: %APPDATA%\My_Photo_Editor\.kivy
# Instead of: %APPDATA%\photoeditor\.kivy

Priority:

KIVY_DESKTOP_PATH_ID takes highest priority and affects:

• KIVY_HOME directory (overrides KIVY_HOME env var and venv detection)

• App.user_data_dir directory

• App.user_cache_dir directory

Platform Behavior:

• Desktop platforms (Windows, macOS, Linux): Uses normalized path_id for directory names

• Mobile platforms (iOS, Android): Ignored - uses App.name as before

Desktop Path Examples with KIVY_DESKTOP_PATH_ID=’My Photo Editor’:

Directory	Path
KIVY_HOME	~/Library/Application Support/My_Photo_Editor/ .kivy (macOS)
user_data_dir	%APPDATA%\My_Photo_Editor (Windows)
user_cache_dir	%LOCALAPPDATA%\My_Photo_Editor\Cache (Windows)

Warning:

If you set KIVY_DESKTOP_PATH_ID in an existing app, your data will move to a new location. You may need to migrate existing data (see Linux migration example above).

For complete documentation, see Controlling the environment and examples/desktop_path_id/. ```

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