Merge pull request #1038 from n-gist/crosshair-initial-canvas-size

Crosshair plugin - initial canvas size fix

src/extras/crosshair.js

@@ -33,6 +33,14 @@ Dygraph.Plugins.Crosshair = (function _extras_crosshair_closure() {
     this.strokeStyle_ = opt_options.strokeStyle || "rgba(0, 0, 0, 0.3)";
   };
 
+  crosshair.prototype.updateCanvasSize = function updateCanvasSize(width, height) {
+    if (width === this.canvas_.width && height === this.canvas_.height) return;
+    this.canvas_.width = width;
+    this.canvas_.height = height;
+    this.canvas_.style.width = width + 'px';    // for IE
+    this.canvas_.style.height = height + 'px';  // for IE
+  };
+
   crosshair.prototype.toString = function toString() {
     return "Crosshair Plugin";
   };
@@ -42,6 +50,7 @@ Dygraph.Plugins.Crosshair = (function _extras_crosshair_closure() {
    * @return {object.<string, function(ev)>} Mapping of event names to callbacks.
    */
   crosshair.prototype.activate = function activate(g) {
+    this.updateCanvasSize(g.width_, g.height_);
     g.graphDiv.appendChild(this.canvas_);
 
     return {
@@ -57,10 +66,7 @@ Dygraph.Plugins.Crosshair = (function _extras_crosshair_closure() {
 
     var width = e.dygraph.width_;
     var height = e.dygraph.height_;
-    this.canvas_.width = width;
-    this.canvas_.height = height;
-    this.canvas_.style.width = width + "px";    // for IE
-    this.canvas_.style.height = height + "px";  // for IE
+    this.updateCanvasSize(width, height);
 
     var ctx = this.canvas_.getContext("2d");
     ctx.clearRect(0, 0, width, height);