Compose playback controls, device recovery contracts, and event cleanup — Connect the previous skills

PART I

Warm-up

Reconnect with a useful idea before starting compose playback controls, device recovery contracts, and event cleanup. In one or two sentences, describe the input, output or host boundary from the previous exercise that this lesson builds on. If you are arriving directly, skim the worked example first; there is no locked prerequisite.

A rough note is enough. You can revise it after the example.

PART II

Instruction & guided example

Connect subscription cleanup to device recovery

Event cleanup is an ownership obligation across registration, delivery, close and late completion. Unregistering a callback and cancelling active native work are different guarantees. WS cancellation signatures remain unresolved, so these lessons specify required host behavior without inventing runtime calls.

Panel P owns device-change registration D and voice V. P closes during device loss. A stale reconnect event is already queued. Policy: closed owners neither resume voices nor create new registrations.

Worked reasoning: Close initiates V cleanup and D release. The stale reconnect delivery checks P closed and does nothing visible or playback-related. Recovery cannot recreate D after its owner ended.

Failed alternative: A reconnect handler that always re-registers leaks a fresh subscription after P close and may restart unwanted sound.

Worked reasoning and supplied artifact

P close ->owner closed;release D; cleanup V
Queued reconnect arrives ->owner closed
No resume V
No new registration D2
Await native cleanup evidence separately

Illustrative example from the proposed WillowScript design. The language and WUIX/WMATH/WDB/WAUDIO/WTMP services are not implemented in the supplied source. This site has no interpreter, VM or native host and does not execute or certify the snippet.

Try the guided change

Reconstruct the supplied worked case first: list its inputs, intermediate decisions and final artifact. Compare each row with the explanation and identify exactly where the rejected alternative fails. Then use the changed inputs in Part IV for independent work.

• Write the supplied inputs and initial state before following the example.
• Reconstruct each intermediate calculation or host decision, then compare with the worked artifact.
• Explain why the contrasting alternative fails before attempting the changed inputs in Part IV.

PART III

Take a breather

Step back after the guided example. Look away from the screen, stretch, or reread your prediction. This is an optional learning pause, not a timer or an assessment gate.

When you return, try to name the lesson’s key idea without copying its wording. If that feels difficult, return to Part II and trace one line rather than restarting the entire lesson.

PART IV

Independent practice

Project context: Media operations console. Build a small, understandable change around compose playback controls, device recovery contracts, and event cleanup.

Trace a stopped owner Q receiving two late reconnect events. State expected new registration and new voice counts.

What to produce

An owner/reconnect/registration/voice ledger with zero post-close acquisitions.

• State the intended behavior in a sentence before editing.
• Use only source-backed syntax and the host services whose contract you have been given.
• Record a normal case and a boundary or unavailable-resource case.
• Label hand predictions separately from anything actually measured in a supplied toolchain.

Syntax colors are a reading aid, not a compiler. The line you are editing stays uncolored until you move to a different line; capitalization is never changed. Drafts stay on this browser and code is not executed.

import wdb;
domain Inventory {
    const lowStock = wdb.query({
        from: products,
        select: [id, name, stock],
        where: [[ stock < 10 ]],
        order: { by: stock, direction: ascending }
    });
}

PART V

Self-check

Use this check to notice what to revisit. It does not award a private course grade, block another page or claim to verify compiled code. Every answer has a learning explanation.

You may keep exploring even if you are unsure. Use the hint, compare the trace, and revise your explanation.

PART VI

Recap & small task

Bring the idea back to the mod feature you are building. A useful recap connects the mechanism to a decision you can make in your own code.

• Connect subscription cleanup to device recovery
• Trace a stopped owner Q receiving two late reconnect events. State expected new registration and new voice counts.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

Prevent both late updates and late reacquisition after owner close.

This marks your personal practice record only. It is not a certification or an official workspace assessment.