+
+ if (this.attr_('underlayCallback')) {
+ // NOTE: we pass the dygraph object to this callback twice to avoid breaking
+ // users who expect a deprecated form of this callback.
+ this.attr_('underlayCallback')(
+ this.hidden_ctx_, this.layout_.getPlotArea(), this, this);
+ }
+
+ var e = {
+ canvas: this.hidden_,
+ drawingContext: this.hidden_ctx_,
+ };
+ this.cascadeEvents_('willDrawChart', e);