Method handler

packages/sanddance/src/viewer.ts:321–323

(n, v)

                await this.vegaViewGl.runAsync();

                const handler: SignalListenerHandler = (n, v) => {
                    this._characterSet.resetCharacterSet(true);
                };

                this.vegaSpec.signals.forEach(s => {
                    this.vegaViewGl.addSignalListener(s.name, handler);