More

Parameter Sliders

The parameter{} element lets educators place interactive sliders in a scene's detail panel. When a student moves a slider, the runtime resolves the new value and delivers it to any element in the same panel whose attribute references that variable.

The educator places a parameter{} in the same detail panel as the plugin and references the variable letter in the plugin's attribute:

scene{
    Adjust the sliders to explore how gravity and particle count affect the system.
}[
    parameter{
        Particle Count
    }(var: n; range: [10, 500]; step: 10; default: 100)

    parameter{
        Gravity
    }(var: g; range: [0.0, 10.0]; step: 0.5; default: 1.0)

    particle-sim(
        particles: n
        gravity: g
        size: (600, 400)
    )
]

When the student moves the Particle Count slider, the runtime resolves n to the new numeric value and delivers the full updated attributes object to the plugin via onAttrsUpdate.

Parameter variable names must be single lowercase letters. The plugin always receives the resolved numeric value — it never sees the variable name itself.

onAttrsUpdate

Registers a handler that fires whenever the resolved value of one or more attributes changes because a parameter slider was moved.

• handler (function; required). Called with the complete attributes object — the same shape as InitContext.attrs.
• Returns void

internote.onInitialize(({ attrs }) => {
  currentAttrs = attrs
  internote.ready()
})

internote.onAttrsUpdate((attrs) => {
  currentAttrs = attrs
})

The attributes object in onAttrsUpdate is the full resolved set — not just the changed keys. Treat it as a complete snapshot of all current values.

Keep a local reference updated by both onInitialize and onAttrsUpdate and read from it in your render loop to avoid stale-closure bugs:

let currentAttrs = {}

internote.onInitialize(({ attrs }) => { currentAttrs = attrs; internote.ready() })
internote.onAttrsUpdate((attrs) => { currentAttrs = attrs })

function tick() {
  simulate(currentAttrs.gravity, currentAttrs.particles)
}