dispose of labels when clearing the cache, #64

js/TickLabelSet.ts

@@ -180,10 +180,21 @@ class TickLabelSet extends Path {
    * symbolic labels (e.g. '2L').
    */
   public invalidateTickLabelSet(): void {
-    this.labelMap.clear();
+    this.clearCache();
     this.update();
   }
 
+  /**
+   * Clears the cache. It is also our responsibility to dispose all labels in the cache, because they were
+   * created by calling createLabel.
+   */
+  private clearCache(): void {
+    for ( const label of this.labelMap.values() ) {
+      label && label.dispose();
+    }
+    this.labelMap.clear();
+  }
+
   public setCreateLabel( createLabel: ( value: number ) => Node | null ): void {
     this.createLabel = createLabel;
     this.invalidateTickLabelSet();