Compose playback controls, device recovery contracts, and event cleanup — Flash-check repair

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

Repair recovery that ignores user stop

A device transition changes what an audio host can currently do, but does not define a universal recovery policy. Track device identity, user intent, position and owner. Resume, reload, restart and remain-paused are distinct decisions that must come from an explicit contract.

V1 loses its device at5s and pauses. The user selects Stop at t2 after loss. Device reconnects at t4. Contract: Stop invalidates the previous resume intent; reconnect cannot resurrect it.

Worked reasoning: Owner playback state becomes stopped at t2. At t4 the device is available, but V1 remains stopped. A fresh Play would create a new intent and operation identity under policy.

Failed alternative: Remembering only wasPlayingBeforeLoss restarts sound despite the users later Stop.

Worked reasoning and supplied artifact

Loss:paused5,resume intent pending
User Stop:stopped,resume intent cleared
Reconnect:device available,V1 still stopped
New Play required for new playback intent

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 Pause, device loss, Stop and reconnect in a timeline. State which latest user action controls the result.

What to produce

A user-intent/device-event ordering ledger and repaired resume guard.

• 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.

• Repair recovery that ignores user stop
• Trace Pause, device loss, Stop and reconnect in a timeline. State which latest user action controls the result.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

Include the latest user intent, not just the state before failure.

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