Reduced motion, tests and limits

Reduced motion

Some people get dizzy or distracted by motion, and turn on “reduce motion” in their system. Pyzed follows that setting, read when the app starts: every animation then shows its resting state at once, without moving.

pz.set_reduced_motion(True) turns motion off, False turns it on, and None follows the system again. Offer it as a setting of your app.
The PYZED_REDUCED_MOTION environment variable (1 or 0) overrides both.

See Accessibility.

Tests and screenshots

Screenshots (App.screenshot, pz.screenshot) always show the resting state: what a mount animation ends on. That keeps tests and documentation images stable, whatever the timing.

To test that a widget animates, check the widget tree: repr(widget) ends with .animate(2 animation(s), 1 transition(s)).

To test a timeline, drive the player by hand. advance runs calls and updates attribute tracks; seek jumps without running calls:

def test_intro_chimes():
    app = Game()
    app.player.owner = app                  # a running app sets it; a test sets it by hand
    app.player.pause()
    app.player.advance(1.7)                 # passes the chime() call at 1.6 s
    assert app.message == "New record!"
    app.player.seek(0.5)
    assert app.player.value("card:y") < 40

A paused player shows its clip at the playhead, even in a screenshot, so you can take a picture of any moment of a clip: app.player.pause(); app.player.seek(0.8); app.screenshot("intro.png").

Limits

Transforms are translation, uniform scale and rotation; there is no skew.
A rotated or blurred widget takes input where its box is laid out, not where it is drawn.
A widget with rotation, blur, backdrop blur or bloom is drawn above its siblings, so its bloom can light the widgets next to it.
backdrop_blur blurs what the window drew before the widget, inside the same parent layer (scrollables and other clipping widgets start a new layer).
width, height, padding and font_size lay the view out again on every frame while they move, so prefer x, y and scale for large views.
Animations restart when a widget leaves the tree and comes back. Give a stable key, or use presence, to control when they replay.
A player plays one clip at a time. To play two scenes at once, use two players.