pythonista-scripter 2020.11.16

iOS Pythonista app UI and Scene animations and UI constraints

SCRIPTER - Pythonista UI and Scene animations

Quick start

In order to start using the animation effects, just import scripter and call the effects as functions:

from scripter import *

hide(my_button)

Effects expect an active UI view as the first argument. Effects run for a default duration of 0.5 seconds, unless otherwise specified with a duration argument.

If you want to create a more complex animation from the effects provided, combine them in a script:

@script
def my_effect(view):
  move(view, 50, 200)
  pulse(view, 'red')
  yield
  hide(view, duration=2.0)

Scripts control the order of execution with yield statements. Here movement and a red pulsing highlight happen at the same time. After both actions are completed, view fades away slowly, in 2 seconds.

As the view provided as the first argument can of course be self or sender, scripts fit naturally as custom ui.View methods or action functions.

As small delays are often needed for natural-feeling animations, you can append a number after a yield statement, to suspend the execution of the script for that duration, or yield 'wait' for the default duration.

Another key for good animations is the use of easing functions that modify how the value progresses from starting value to the target value. Easing functions support creating different kinds of accelerating, bouncing and springy effects. Easing functions can be added as an argument to scripts:

slide_value(view, 'x', 200, ease_func=bounce_out)

See this reference to pick the right function, or run scripter-demo.py to try out the available effects and to find the optimal duration and easing function combo for your purposes.

You can change the default speed of all animations by setting Scripter.default_duration.

Scripter can also be used to animate different kinds of Pythonista scene module Nodes, including the Scene itself. Scripter provides roughly the same functionality as scene.Action, but is maybe a bit more concise, and is available as an option if you want to use same syntax in both UI and Scene projects.

See the API documentation for individual effects and how to roll your own with set_value, slide_value and timer.

There are also convenience functions, not separately documented, corresponding to all animatable attributes of ui views. For example, you can animate the ui.View.background_color attribute with:

background_color(view, 'black')

API

• Class: Scripter
  • Methods
  • Properties
• Class: ScrollingBannerLabel
  • Methods
  • Properties
• Class: Vector
  • Methods
  • Properties
• Functions
  • Script management
  • Animation primitives
  • Animation effects
  • Easing functions

Class: Scripter

Class that contains the update method used to run the scripts and to control their execution.

Runs at default 60 fps, or not at all when there are no scripts to run.

Inherits from ui.View; constructor takes all the same arguments as ui.View.

Methods

update(self)

Main Scripter animation loop handler, called by the Puthonista UI loop and never by your code directly.

This method:

• Activates all newly called scripts and suspends their parents.
• Calls all active scripts, which will run to their next yield or until completion.
• As a convenience feature, if a yield returns 'wait' or a specific duration, kicks off a child timer script to wait for that period of time.
• Cleans out completed scripts.
• Resumes parent scripts whose children have all completed.
• Sets update_interval to 0 if all scripts have completed.

pause_play_all(self)

Pause or play all animations.

cancel(self, script)

Cancels any ongoing animations and sub-scripts for the given script.

cancel_all(self)

Initializes all internal structures. Used at start and to cancel all running scripts.

Properties

default_update_interval (get)

The running rate for the update method. Frames per second is here considered to be just an alternative way of setting the update interval, and this property is linked to default_fps - change one and the other will change as well.

default_fps (get)

The running rate for the update method. Frames per second is here considered to be just an alternative way of setting the update interval, and this property is linked to default_update_interval - change one and the other will change as well.

Class: ScrollingBannerLabel

UI component that scrolls the given text indefinitely, in either direction. Will only scroll if the text is too long to fit into this component.

Methods

__init__(self, **kwargs)

In addition to normal ui.View arguments, you can include:

• text - To be scrolled as a marquee.
• Label formatting arguments font and text_color.
• initial_delay - How long we wait before we start scrolling, to enable reading the beginning of the text. Default is 2 seconds.
• scrolling_speed - How fast the text moves, in points per second. Default is 100 pts/s.
• to_right - Set to True if you would like the text to scroll from the left. Default is False.

stop(self)

Stops the scrolling and places the text at start.

restart(self)

Restarts the scrolling, including the initial delay, if any.

Properties

text (get)

You can change the text displayed at any point after initialization by setting this property.

Functions

SCRIPT MANAGEMENT

script(func)

Can be used with Scene Nodes.

Decorator for the animation scripts. Scripts can be functions, methods or generators.

First argument of decorated functions must always be the view to be animated.

Calling a script starts the Scripter update loop, if not already running.

New scripts suspend the execution of the parent script until all the parallel scripts have completed, after which the update method will resume the execution of the parent script.

find_scripter_instance(view)

Can be used with Scene Nodes.

Scripts need a "controller" ui.View that runs the update method for them. This function finds or creates the controller for a view as follows:

1. Check if the view itself is a Scripter
2. Check if any of the subviews is a Scripter
3. Repeat 1 and 2 up the view hierarchy of superviews
4. If not found, create an instance of Scripter as a hidden subview of the root view

In case of scene Nodes, search starts from node.scene.view.

If you want cancel or pause scripts, and have not explicitly created a Scripter instance to run them, you need to use this method first to find the right one.

ANIMATION PRIMITIVES

set_value(view, attribute, value, func=None)

@script

Generator that sets the attribute to a value once, or several times if the value itself is a generator or an iterator.

Optional keyword parameters:

• func - called with the value, returns the actual value to be set

slide_value(view, attribute, end_value, target=None, start_value=None, duration=None, delta_func=None, ease_func=None, current_func=None, map_func=None, side_func=None)

@script

Generator that "slides" the value of an attribute to an end_value in a given duration.

Optional keyword parameters:

• start_value - set if you want some other value than the current value of the attribute as the animation start value.
• duration - time it takes to change to the target value. Default is 0.5 seconds.
• delta_func - use to transform the range from start_value to end_value to something else.
• ease_func - provide to change delta-t value to something else. Mostly used for easing; you can provide an easing function name as a string instead of an actual function. See supported easing functions here.
• current_func - Given the start value, delta value and progress fraction (from 0 to 1), returns the current value. Intended to be used to manage more exotic values like colors.
• map_func - Used to translate the current value to something else, e.g. an angle to a Transform.rotation.
• side_func - Called without arguments each time after the main value has been set. Useful for side effects.

slide_tuple(view, *args, **kwargs)

@script

Slide a tuple value of arbitrary length. Supports same arguments as slide_value.

slide_color(view, attribute, end_value, **kwargs)

@script

Slide a color value. Supports the same arguments as slide_value.

timer(view, duration=None, action=None)

@script

Acts as a wait timer for the given duration in seconds. view is only used to find the controlling Scripter instance. Optional action function is called every cycle.

ANIMATION EFFECTS

center(view, move_center_to, **kwargs)

@script

Move view center (anchor for Scene Nodes).

center_to(view, move_center_to, **kwargs)

@script

Alias for center.

center_by(view, dx, dy, **kwargs)

@script

Adjust view center/anchor position by dx, dy.

expand(view, **kwargs)

@script

Not applicable for Scene Nodes.

Expands the view to fill all of its superview.

fly_out(view, direction, **kwargs)

@script

Moves the view out of the screen in the given direction. Direction is one of the following strings: 'up', 'down', 'left', 'right'.

hide(view, **kwargs)

@script

Fade the view away.

move(view, x, y, **kwargs)

@script

Move to x, y. For UI views, this positions the top-left corner. For Scene Nodes, this moves the Node position.

move_to(view, x, y, **kwargs)

@script

Alias for move.

move_by(view, dx, dy, **kwargs)

@script

Adjust position by dx, dy.

pulse(view, color='#67cf70', **kwargs)

@script

Pulses the background of the view to the given color and back to the original color. Default color is a shade of green.

reveal_text(view, **kwargs)

@script

Reveals text one letter at a time in the given duration. View must have a text attribute.

roll_to(view, to_center, end_right_side_up=True, **kwargs)

@script

Roll the view to a target position given by the to_center tuple. If end_right_side_up is true, view starting angle is adjusted so that the view will end up with 0 rotation at the end, otherwise the view will start as-is, and end in an angle determined by the roll. View should be round for the rolling effect to make sense. Imaginary rolling surface is below the view - or to the left if rolling directly downwards.

rotate(view, degrees, shortest=False, **kwargs)

@script

Rotate view to an absolute angle. Set start_value if not starting from 0. Positive number rotates clockwise. For UI views, does not mix with other transformations.

Optional arguments:

• shortest - If set to True (default), will turn in the "right" direction. For UI views, start_value must be set to a sensible value for this to work.

rotate_to(view, degrees, **kwargs)

Alias for rotate.

rotate_by(view, degrees, **kwargs)

@script

Rotate view by given degrees.

scale(view, factor, **kwargs)

@script

Scale view to a given factor in both x and y dimensions. For UI views, you need to explicitly set start_value if not starting from 1.

scale_to(view, factor, **kwargs)

Alias for scale.

scale_by(view, factor, **kwargs)

@script

Scale view relative to current scale factor.

show(view, **kwargs)

@script

Slide alpha from 0 to 1.

wobble(view)

@script

Little wobble of a view, intended to attract attention.

wait_for_tap(view)

@script

Overlays the given view with a temporary transparent view, and yields until the view is tapped.

EASING FUNCTIONS

mirror(ease_func, t)

Runs the given easing function to the end in half the duration, then backwards in the second half. For example, if the function provided is linear, this function creates a "triangle" from 0 to 1, then back to 0; if the function is ease_in, the result is more of a "spike".

oscillate(t)

Basic sine curve that runs from 0 through 1, 0 and -1, and back to 0.