cleaner deeptable instantiation pattern

src/Deeptable.ts

@@ -138,15 +138,57 @@
     // Must come after manifest is set.
     this.base_url = baseUrl;
     this.root_tile = new Tile(defaultManifest, null, this);
-    const preProcessRootTile = this.root_tile.preprocessRootTileInfo();
-
     // At instantiation, the deeptable isn't ready; only once this
     // async stuff is done can the deeptable be used.
     // TODO: Add an async static method as the preferred initialization method.
-    this.promise = preProcessRootTile.then(async () => {
+    this.promise = this._makePromise(defaultManifest);
+  }
+
+  /**
+   * Loads a quadtree created by version 2.0 or great of the quadfeather package (including manifests).
+   *
+   * @param tileProxy A tileProxy to use for fetching tiles. Can be used to wrap authentication.
+   * @param baseUrl The base URL of the quadfeather data.
+   *
+   */
+  static async fromQuadfeather({
+    tileProxy,
+    baseUrl,
+    plot = null,
+  }: {
+    tileProxy?: DS.TileProxy;
+    baseUrl: string;
+    plot?: Scatterplot | null;
+  }) {
+    let manifest: DS.TileManifest;
+    if (tileProxy !== undefined) {
+      throw new Error('Not yet supported');
+    } else {
+      manifest = await loadTileManifest(baseUrl + '/manifest.feather');
+    }
+
+    const dt = new Deeptable({
+      tileProxy,
+      tileManifest: manifest,
+      baseUrl,
+      rootKey: '0/0/0',
+      plot,
+    });
+    await dt.promise;
+    return dt;
+  }
+
+  /**
+   * Internal function to ensure
+   */
+  protected _makePromise(
+    tileManifest: Partial<DS.TileManifest> & { key: string },
+  ): Promise<void> {
+    return this.root_tile.preprocessRootTileInfo().then(async () => {
       const batch = await this.root_tile.get_arrow(null);
       const schema = batch.schema;
-      if (!tileManifest) {
+      // TODO: Cleaner check that it's a lazy manifest
+      if (!tileManifest.max_ix) {
         this.root_tile.manifest =
           await this.root_tile.deriveManifestInfoFromTileMetadata();
       }
@@ -368,7 +410,7 @@
       if (dim === undefined) {
         continue;
       }
       dim = (dim as Field<Struct<any>>).type.children.find(
         (d) => d.name === sub,
       );
     }
@@ -388,7 +430,7 @@
         max = JSON.parse(mmax) as T[0];
       }
       // Can pass min, max as strings for dates.
       if (dim.type.typeId === Type.Timestamp) {
         if (typeof min !== 'string' || typeof max !== 'string') {
           throw new Error(
             'Date field extents in metadata must be passed as strings',
@@ -1188,7 +1230,7 @@
   extent: Rectangle;
 };
 
-export async function tileManifest(url: string) {
+export async function loadTileManifest(url: string): Promise<TileManifest> {
   const data = await fetch(url).then((d) => d.arrayBuffer());
   const tb = tableFromIPC(data);
   const rows: RowFormatManifest[] = [...tb].map(

src/scatterplot.ts

@@ -373,7 +373,11 @@
     tileProxy,
   }: DS.DataSpec): Promise<DS.Deeptable> {
     if (source_url !== undefined) {
-      this._root = Deeptable.from_quadfeather(source_url, this, tileProxy);
+      this._root = await Deeptable.fromQuadfeather({
+        baseUrl: source_url,
+        plot: this,
+        tileProxy,
+      });
     } else if (arrow_table !== undefined) {
       this._root = Deeptable.fromArrowTable(arrow_table, this);
     } else if (arrow_buffer !== undefined) {
@@ -614,7 +618,7 @@
   }
 
   get highlit_point_change(): ChangeToHighlitPointFunction['f'] {
     return this.handle_highlit_point_change.f.bind(
       this.handle_highlit_point_change,
     );
   }
@@ -695,7 +699,7 @@
       }
       //
       const needed_keys = neededFieldsToPlot(prefs.encoding);
       this.deeptable.root_tile.require_columns(
         [...needed_keys].map((k) => k[0]),
       );
       // Immediately start loading what we can onto the GPUs, too.
@@ -713,7 +717,7 @@
    *
    * @param prefs An API call.
    */
   private async unsafe_plotAPI(prefs: DS.APICall): Promise<void> {
     if (prefs === null) {
       return;
     }