Merge branch 'master' of github.com:danvk/dygraphs

[dygraphs.git] / dygraph-layout.js

diff --git a/dygraph-layout.js b/dygraph-layout.js
index 99ae50c..c870d3b 100644 (file)
--- a/dygraph-layout.js
+++ b/dygraph-layout.js
@@ -129,32 +129,70 @@ DygraphLayout.prototype._evaluateLimits = function() {
 DygraphLayout.prototype._evaluateLineCharts = function() {
   // add all the rects
   this.points = new Array();
+  // An array to keep track of how many points will be drawn for each set.
+  // This will allow for the canvas renderer to not have to check every point
+  // for every data set since the points are added in order of the sets in
+  // datasets.
+  this.setPointsLengths = new Array();
+
   for (var setName in this.datasets) {
     if (!this.datasets.hasOwnProperty(setName)) continue;
 
     var dataset = this.datasets[setName];
     var axis = this.dygraph_.axisPropertiesForSeries(setName);
 
+    var graphWidth = this.dygraph_.width_;
+    var graphHeight = this.dygraph_.height_;
+    var prevXPx = NaN;
+    var prevYPx = NaN;
+    var currXPx = NaN;
+    var currYPx = NaN;
+    var setPointsLength = 0;
+
+    // Ignore the pixel skipping optimization if there are error bars.
+    // XXX 2011-07-25 temporarily disabled (see autotests/tests/selection.js)
+    var skip_opt = (true ||
+                    this.attr_("errorBars") ||
+                    this.attr_("customBars") ||
+                    this.annotations.length > 0);
+
     for (var j = 0; j < dataset.length; j++) {
       var item = dataset[j];
+      var xValue = parseFloat(dataset[j][0]);
+      var yValue = parseFloat(dataset[j][1]);
 
-      var yval;
+      // Range from 0-1 where 0 represents top and 1 represents bottom
+      var xNormal = (xValue - this.minxval) * this.xscale;
+      // Range from 0-1 where 0 represents left and 1 represents right.
+      var yNormal;
       if (axis.logscale) {
-        yval = 1.0 - ((Dygraph.log10(parseFloat(item[1])) - Dygraph.log10(axis.minyval)) * axis.ylogscale); // really should just be yscale.
+        yNormal = 1.0 - ((Dygraph.log10(yValue) - Dygraph.log10(axis.minyval)) * axis.ylogscale);
       } else {
-        yval = 1.0 - ((parseFloat(item[1]) - axis.minyval) * axis.yscale);
+        yNormal = 1.0 - ((yValue - axis.minyval) * axis.yscale);
+      }
+
+      // Current pixel coordinates that the data point would fill.
+      currXPx = Math.round(xNormal * graphWidth);
+      currYPx = Math.round(yNormal * graphHeight);
+
+      // Skip over pushing points that lie on the same pixel.
+      // TODO(antrob): optimize this for graphs with error bars.
+      if (skip_opt || prevXPx != currXPx || prevYPx != currYPx) {
+        var point = {
+          // TODO(danvk): here
+          x: xNormal,
+          y: yNormal,
+          xval: xValue,
+          yval: yValue,
+          name: setName
+        };
+        this.points.push(point);
+        setPointsLength += 1;
       }
-      var point = {
-        // TODO(danvk): here
-        x: ((parseFloat(item[0]) - this.minxval) * this.xscale),
-        y: yval,
-        xval: parseFloat(item[0]),
-        yval: parseFloat(item[1]),
-        name: setName
-      };
-
-      this.points.push(point);
+      prevXPx = currXPx;
+      prevYPx = currYPx;
     }
+    this.setPointsLengths.push(setPointsLength);
   }
 };