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RejectedErrorHandling.md

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Rejected Fatal Error Handling Revisions

Appendix document for ErrorHandling.md.

Revisions in this document were rejected by the author (@kainino0x) before publishing. They are kept for posterity, as examples of previous ideas.

Revision 3-ish

The GPUAdapter and GPUDevice are event targets which receive events about adapter and device status.

partial interface GPUAdapter : EventTarget {
    readonly attribute boolean isReady;
};

interface GPUAdapterLostEvent : Event {
    readonly attribute DOMString reason;
};

interface GPUAdapterReadyEvent : Event {};
partial interface GPUDevice : EventTarget {};

interface GPUDeviceLostEvent : Event {
    readonly attribute boolean recoverable;
    readonly attribute DOMString reason;
};

If GPUAdapter's isReady attribute is false, createDevice will fail. isReady may be set to false when a "gpu-device-lost" event fires. It will always be set to true when a "gpu-adapter-ready" event fires.

  • GPUAdapter "gpu-adapter-lost" -> GPUAdapterLostEvent: Signals that the GPUAdapter cannot be used anymore. Sets the adapter's status to "invalid". Any further createDevice calls will return invalid objects.

  • GPUAdapter "gpu-adapter-ready" -> GPUAdapterReadyEvent: Signals when it is okay to create new devices on this adapter. It may fire only if:

    • the adapter is still valid,
    • the adapter's isReady attribute is true, and
    • the adapter's isReady attribute was false.

  • GPUDevice "gpu-device-lost" -> GPUDeviceLostEvent: Signals that the GPUDevice cannot be used anymore. Sets the status of the device and its objects to "invalid". (The "gpulogentry" event will not fire after a device loss, so this makes all further operations on the device effectively no-ops.) This may happen if something goes fatally wrong on the device (e.g. unexpected out-of-memory, crash, or native device loss). When this event is handled, the adapter's isReady attribute may be false, which indicates the application cannot make new devices. This event may cause the adapter's isReady attribute to become false.

Rejected

This scheme requires apps to do a spaghettical incantation in order to know what to do, and when. It involves listening to all of these events, diligently checking flags in the event handlers, and understanding weird races (like an adapter became ready and then was immediately lost, or an adapter became ready and then vends an immediately lost device).