Handle an explicit window-close event — Review and demonstrate

PART I

Warm-up

Reconnect with a useful idea before starting handle an explicit window-close event. 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

Review close behavior under repeated delivery

Closing a window ends an owner, not all work everywhere. A window-close event is a host lifecycle signal. The source leaves cancellation methods and exact late-result rules unresolved, so use an explicit exercise contract. Closing one owner must not silently cancel another owner or grant a late callback permission to update an unrelated screen.

The host may deliver the same close notification twice. W11 owns one temporary preview artifact P11. Cleanup is a host operation that may report AlreadyAbsent after the first successful release.

Track window identity, operation identity, dirty local work, and delivery time. Distinguish the user requesting close from the host confirming close. Whether close may be delayed, whether a draft is retained, and who completes cleanup are contract decisions. Worked case: First delivery moves W11 to Closed and releases P11. Second delivery sees Closed and AlreadyAbsent; the required final state remains Closed with no owned preview artifact. The response must not decrement shared accounting twice or report a new user failure.

Compare the tempting alternative: Assuming exactly-once delivery makes the second notification a hidden corruption case. Releasing another owner’s artifact to compensate is outside the contract.

Worked reasoning and supplied artifact

// Paper trace / supplied exercise-host contract; no execution claimed.
// The host may deliver the same close notification twice. W11 owns one temporary preview artifact P11. Cleanup is a host operation that may report AlreadyAbsent after the first successful release.
// First delivery moves W11 to Closed and releases P11. Second delivery sees Closed and AlreadyAbsent; the required final state remains Closed with no owned preview artifact. The response must not decrement shared accounting twice or report a new user failure.

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: Support request workflow. Build a small, understandable change around handle an explicit window-close event.

Specify an idempotent close-state decision and trace successful release, AlreadyAbsent and genuine cleanup failure separately.

What to produce

A three-outcome cleanup table with repeated-delivery behavior.

• 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 wuix.widget;
import app;
domain Workspace {
    const application = Application({
        name: "Workspace",
        window: { title: "Dashboard", size: [1280, 800] },
        events: {
            "app.ready": fnc() -> void { console.log("Ready"); }
        }
    });
}

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.

• Review close behavior under repeated delivery
• Specify an idempotent close-state decision and trace successful release, AlreadyAbsent and genuine cleanup failure separately.
• Separate source-backed behavior, host requirements and untested predictions.

One small recap task

Explain why AlreadyAbsent differs from a new cleanup failure.

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