add some comments

[dygraphs.git] / dygraph.js

diff --git a/dygraph.js b/dygraph.js
index abd2973..8979c6f 100644 (file)
--- a/dygraph.js
+++ b/dygraph.js
@@ -2332,6 +2332,9 @@ Dygraph.prototype.drawGraph_ = function() {
 Dygraph.prototype.renderGraph_ = function(is_initial_draw) {
   this.plotter_.clear();
   this.plotter_.render();
+
+  // TODO(danvk): is this a performance bottleneck when panning?
+  // The interaction canvas should already be empty in that situation.
   this.canvas_.getContext('2d').clearRect(0, 0, this.canvas_.width,
                                           this.canvas_.height);