- * Update the graph with new data. Data is in the format
- * [ [date1, val1, val2, ...], [date2, val1, val2, ...] if errorBars=false
- * or, if errorBars=true,
- * [ [date1, [val1,stddev1], [val2,stddev2], ...], [date2, ...], ...]
- * @param {Array.<Object>} data The data (see above)
+ * This function is called once when the chart's data is changed or the options
+ * dictionary is updated. It is _not_ called when the user pans or zooms. The
+ * idea is that values derived from the chart's data can be computed here,
+ * rather than every time the chart is drawn. This includes things like the
+ * number of axes, rolling averages, etc.
+ */
+Dygraph.prototype.predraw_ = function() {
+ // TODO(danvk): move more computations out of drawGraph_ and into here.
+ this.computeYAxes_();
+
+ // Create a new plotter.
+ if (this.plotter_) this.plotter_.clear();
+ this.plotter_ = new DygraphCanvasRenderer(this,
+ this.hidden_, this.layout_,
+ this.renderOptions_);
+
+ // The roller sits in the bottom left corner of the chart. We don't know where
+ // this will be until the options are available, so it's positioned here.
+ this.createRollInterface_();
+
+ // Same thing applies for the labelsDiv. It's right edge should be flush with
+ // the right edge of the charting area (which may not be the same as the right
+ // edge of the div, if we have two y-axes.
+ this.positionLabelsDiv_();
+
+ // If the data or options have changed, then we'd better redraw.
+ this.drawGraph_();
+};
+
+/**
+=======
+ * Update the graph with new data. This method is called when the viewing area
+ * has changed. If the underlying data or options have changed, predraw_ will
+ * be called before drawGraph_ is called.