Application Events¶

In addition to mouse and keyboard input, Datoviz supports two types of programmatic event callbacks:

Frame callbacks: triggered at every rendered frame
Timers: triggered at fixed time intervals

These are useful for animations, simulation steps, or triggering regular updates independent of user input.

Frame events¶

Frame events are called once per render loop iteration. They allow you to update visuals or application state continuously, such as animating objects or polling data.

To register a frame event handler, decorate a function named on_frame:

@app.connect(figure)
def on_frame(ev):
    # Update something every frame
    print("Rendering frame")

Triggered once per frame (hundreds of thousands of frames per second by default, ~60 FPS or the monitor refresh rate when the environment variable DVZ_VSYNC=1 activates vertical synchronization)
Bound to a specific Figure
Receives an event object (ev), though it is typically unused

Avoid any computationally intensive operations in this function to prevent frame rate drops.

Timer events¶

Use timers to trigger a function at regular time intervals.

@app.timer(delay=0.0, period=1.0, max_count=0)
def my_timer(ev):
    print("Timer tick")

Parameters:¶

Argument	Description
`delay`	Initial delay in seconds before the timer starts
`period`	Time between calls (in seconds)
`max_count`	Maximum number of timer calls (0 = unlimited)

Summary¶

Event type	Trigger	Use case
`on_frame`	Every render frame	Animations, continuous updates
`@app.timer`	Fixed interval (in seconds)	Simulation steps, timed triggers

These callbacks provide core building blocks for interactive and time-based applications in Datoviz.