datasets for sketches

docs/js/custom-element/api/graphics-api.js

@@ -138,6 +138,19 @@ class GraphicsAPI extends BaseAPI {
     points.forEach((p) => this.movable.push(p));
   }
 
+  /**
+   * Get a parameter specified via data-attribute
+   */
+  getParameter(name, fallback) {
+    let val = this.dataset[name];
+    if (val) {
+      let asFloat = parseFloat(val);
+      if (val == asFloat) return asFloat;
+      return val;
+    }
+    return fallback;
+  }
+
   /**
    * Set up a slider to control a named, numerical property in the sketch.
    *