Doenet assignment viewer

View assignments from questions written in DoenetML

Mixed DoenetML versions

Each document in an assignment carries its own DoenetML version, and every embedded viewer downloads and parses the multi-MB standalone bundle for its document's version — so an assignment mixing versions multiplies that cost by the number of distinct versions on the page.

The viewer does not normalize versions itself (that would change how the older documents behave). Instead, when an assignment mixes versions, it reports the condition to the containing page — a console warning alone would be invisible to the site's visitors — via the reportWarningsCallback prop, and the page decides how to display it:

<ActivityViewer
    source={source}
    reportWarningsCallback={(warnings) => {
        for (const warning of warnings) {
            if (warning.type === "mixedDoenetmlVersions") {
                showBanner(
                    `This assignment mixes DoenetML versions (${warning.versions.join(", ")}), ` +
                        "which slows loading. Consider updating its documents to one version.",
                );
            }
        }
    }}
/>

To consolidate, normalize the documents' version fields in the assignment source. Saved student state survives such a change: it is keyed on a source hash that deliberately ignores version.

Windowed mounting

Every item's viewer component is always mounted, but memory tracks what the student can see — the pagination window or viewport — instead of the assignment's length. The embedded viewers register with a page-wide windowed mounting policy (mountPolicy from @doenet/doenetml-iframe): items only boot their iframe (a multi-MB bundle parse plus a core worker) when near the viewport or within the pagination window, simultaneous boots are capped, and at most maxLiveViewers stay live — the rest are parked: their state is flushed, their iframe is replaced by a placeholder, and they are restored (student's typed work intact) when the student returns to them. In paginated mode the current page and its neighbors are kept live, so page flips within the window stay instant.

This is the default. Tune it with the mountPolicy prop (overrides for maxLiveViewers, visibleMargin, parkDelayMs, flushTimeoutMs, maxConcurrentBoots):

<ActivityViewer
    source={source}
    flags={{ allowSaveState: true }}
    mountPolicy={{ maxLiveViewers: 5 }}
/>

Parking requires a persistence path (flags.allowSaveState or flags.allowLocalState) so no student work can be lost; without one, viewers still mount lazily but stay live once booted.

To cut the per-document core cost further, useSharedCoreWorker serves all documents' cores from a shared worker pool instead of one dedicated ~100 MB worker per document (default off; see @doenet/doenetml-iframe).