`<perspective-viewer>` Custom Element library

<perspective-viewer> provides a complete graphical UI for configuring the perspective library and formatting its output to the provided visualization plugins.

Once imported and initialized in JavaScript, the <perspective-viewer> Web Component will be available in any standard HTML on your site. A simple example:

<perspective-viewer id="view1"></perspective-viewer>
<script type="module">
    import perspective from "@perspective-dev/client";
    import "@perspective-dev/viewer";

    const viewer = document.getElementById("view1");
    const worker = await perspective.worker();
    await worker.table(data, { name: "my_table" });

    await viewer.load(worker);
    await viewer.restore({ table: "my_table" });
</script>

load() binds the viewer to a Client, and restore() selects which of that client’s Tables to show via the table field. Because load() alone selects no table, it does not render — the pair guarantees exactly one atomic render.

Passing a Table directly is still supported as a legacy shorthand,

await viewer.load(table);

… which is internally equivalent to:

await viewer.load(await table.get_client());
await viewer.restore({ table: await table.get_name() });

Always give your Table a name. When name is omitted a random one is assigned, so the table field in a token from save() will not match the table after a page reload, and restore() will fail.

Attributes

<perspective-viewer> can be configured via HTML attributes or JavaScript properties. When set as attributes, the viewer will apply the configuration on initialization:

<perspective-viewer
    columns='["Sales", "Profit"]'
    group-by='["Region"]'
    sort='[["Sales", "desc"]]'>
</perspective-viewer>

UI Features

The viewer provides an interactive side panel with:

Column list - drag and drop columns to configure group_by, split_by, sort, and filter fields.
New Column button - opens an expression editor for creating computed columns via the expression language.
Plugin selector - switch between the visualization plugins registered on the page. @perspective-dev/viewer-datagrid provides Datagrid; @perspective-dev/viewer-charts provides X Bar, Y Bar, Y Line, Y Scatter, Y Area, X/Y Scatter, X/Y Line, Density, Treemap, Sunburst, Heatmap, Candlestick, OHLC, Map Scatter, Map Line and Map Density.
Theme selector - toggle between available themes.
Export - download the current view as CSV or Arrow.
Copy - copy the current view to the clipboard.
Reset - restore the viewer to its default configuration.

Methods

A <perspective-viewer> hosts one or more panels. Methods which address a single panel take an options-dict with an optional panel id, defaulting to the active panel — e.g. await viewer.save({ panel: "PANEL_ID_0" }).

Binding

Method	Description
`load(client)`	Bind a `Client` (or, legacy, a `Table`) to the viewer
`eject(options?)`	Remove a `Client` and dispose every panel bound to it
`delete()`	Release the element’s resources
`getClient(options?)`	Get a bound `Client`
`getTable(options?)`	Get a panel’s `Table`
`getView(options?)`	Get a panel’s `View`
`getViewConfig(options?)`	Get a panel’s `ViewConfig`

Configuration

Method	Description
`save(options?)`	Serialize one panel’s configuration
`restore(config, options?)`	Apply a configuration to one panel
`saveWorkspace()`	Serialize the whole element — every panel, plus layout and global filters
`restoreWorkspace(config)`	Restore a whole-element configuration
`reset(all?, options?)`	Reset configuration (pass `true` to also reset expressions)
`resetError()`	Clear the error overlay

Panels

Method	Description
`addPanel(config)`	Add a panel, returning its generated id
`removePanel(id)`	Remove a panel
`getPanelNames()`	List panel ids
`getActivePanel()` / `setActivePanel(id)`	Get or set the active panel

Output

Method	Description
`export(options?)`	Export a panel — see the export methods below
`download(options?)`	Export and download as a file
`copy(options?)`	Copy a panel to the clipboard

export(), download() and copy() all take a method, one of "csv", "json", "ndjson" or "arrow" — each with -all and -selected variants (e.g. "csv-selected") — plus "html", "json-config", and "plugin". The "plugin" method asks the plugin to render itself, which produces a PNG for charts and text for the datagrid. | getSelection(options?) / setSelection(...) | Get or set the selected region | | getEditPort(options?) | Get a panel’s edit port | | getRenderStats(options?) | Get render timing statistics |

Rendering and chrome

Method	Description
`flush()`	Wait for any pending UI updates to complete
`resize(options?)`	Redraw, optionally at a `{dimensions: {width, height}}` size hint
`setAutoSize(bool)` / `setAutoPause(bool)` / `setThrottle(ms)`	Render policy
`toggleConfig(force?)`	Toggle the settings sidebar
`toggleColumnSettings(...)`	Toggle the column settings sidebar
`resetThemes(themes?)`	Re-detect or explicitly set available themes
`restyleElement()`	Re-read CSS and repaint
`getPlugin(name?)` / `getAllPlugins()`	Look up registered plugins

See Saving and restoring UI state for the save/restore formats and the panel selector, and Plugin render limits for getPlugin.

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