Timer

run code on a delay or at a repeating interval.

▶ Run in browser

Tags: 2d timer signals

A Timer is a node that emits a timeout signal after its duration. Set one_shot=False to repeat. Here a repeating timer spawns a pulse every 0.8s, and each pulse uses its own one-shot timer to remove itself after one second, so the screen stays lively without any per-frame bookkeeping in the root.

What it demonstrates

  • Timer(duration=, one_shot=, autostart=) – a node that fires timeout after a delay.

  • timer.timeout.connect(fn) – run something when it fires (a signal, like any other).

  • Repeating timers (one_shot=False) for intervals; one-shot timers for delayed actions.

Source

 1"""Timer: run code on a delay or at a repeating interval.
 2
 3A `Timer` is a node that emits a `timeout` signal after its `duration`. Set
 4`one_shot=False` to repeat. Here a repeating timer spawns a pulse every 0.8s, and
 5each pulse uses its own one-shot timer to remove itself after one second, so the
 6screen stays lively without any per-frame bookkeeping in the root.
 7
 8# /// simvx
 9# tags = ["2d", "timer", "signals"]
10# screenshot_frame = 90
11# web = { root = "TimerDemo", width = 800, height = 600, responsive = true }
12# ///
13
14## What it demonstrates
15
16- `Timer(duration=, one_shot=, autostart=)` -- a node that fires `timeout` after a delay.
17- `timer.timeout.connect(fn)` -- run something when it fires (a signal, like any other).
18- Repeating timers (`one_shot=False`) for intervals; one-shot timers for delayed actions.
19"""
20
21import random
22
23from simvx.core import Node2D, Timer, Vec2
24from simvx.graphics import App
25
26WIDTH, HEIGHT = 800, 600
27
28
29class Pulse(Node2D):
30    """An expanding, fading ring that deletes itself after one second."""
31
32    LIFE = 1.0
33    # The ring expands and fades every frame -> opt into per-frame redraw so the
34    # retained 2D renderer re-runs on_draw instead of freezing the first frame.
35    dynamic = True
36
37    def on_ready(self):
38        self.age = 0.0
39        timer = self.add_child(Timer(duration=self.LIFE, one_shot=True, autostart=True))
40        timer.timeout.connect(self.destroy)  # one-shot: clean up after the delay
41
42    def on_update(self, dt: float):
43        self.age += dt
44
45    def on_draw(self, renderer):
46        f = min(1.0, self.age / self.LIFE)
47        renderer.draw_circle(self.position, 12 + f * 64, colour=(0.4, 0.8, 1.0, 1.0 - f), filled=True)
48
49
50class TimerDemo(Node2D):
51    def on_ready(self):
52        self.ticks = 0
53        spawner = self.add_child(Timer(duration=0.8, one_shot=False, autostart=True))
54        spawner.timeout.connect(self._spawn)  # repeating: fires every 0.8s
55
56    def _spawn(self):
57        self.ticks += 1
58        # Spawn against the live window size so pulses keep filling the view
59        # after a resize (the web export runs this scene responsively).
60        w, h = self.app.width, self.app.height
61        self.add_child(Pulse(position=Vec2(random.uniform(120, w - 120), random.uniform(140, h - 100))))
62
63    def on_draw(self, renderer):
64        renderer.draw_text("Timer: repeating + one-shot", (20, 20), scale=2, colour=(1, 1, 1))
65        renderer.draw_text(f"ticks: {self.ticks}", (20, 52), scale=1, colour=(0.7, 0.7, 0.7))
66
67
68if __name__ == "__main__":
69    App(title="Timer", width=WIDTH, height=HEIGHT).run(TimerDemo())