Code to aggregate histograms together

lib/torque/leaflet/torque.js

@@ -25,6 +25,8 @@ L.TorqueLayer = L.CanvasLayer.extend({
     if (!torque.isBrowserSupported()) {
       throw new Error("browser is not supported by torque");
     }
+
+    this._histograms = []
     options.tileLoader = true;
     this.key = 0;
     this.prevRenderedKey = 0;
@@ -93,6 +95,10 @@ L.TorqueLayer = L.CanvasLayer.extend({
         // don't load tiles that are not being shown
         if (t.zoom !== self._map.getZoom()) return;
         self._tileLoaded(t, tileData);
+        if(Object.keys(tileData.histogram).length > 0){
+          self._addTileHistogram(t.x,t.y,t.zoom, tileData.histogram)
+        }
+
         self._clearTileCaches();
         if (tileData) {
           self.redraw();
@@ -102,7 +108,66 @@ L.TorqueLayer = L.CanvasLayer.extend({
     }, this);
 
   },
+  _invalidateHistograms:function(){
+    this._histograms= undefined
+  },
+  _addTileHistogram:function(x, y, zoom, histogram){
 
+    this._histograms[zoom] = this._histograms[zoom] ? this._histograms[zoom] : []
+    this._histograms[zoom][x] = this._histograms[zoom][x] ? this._histograms[zoom][x] : []
+    this._histograms[zoom][x][y] = histogram
+    this.fire('histogramAdded')
+  },
+  histogramForVariable:function(variable){
+    histogramParts=[]
+    Object.keys(this._tiles).forEach(function(t){
+      var coord = t.split(":")
+      if(this._histograms[coord[2]][coord[0]][coord[1]]){
+        histogramParts.push(this._histograms[coord[2]][coord[0]][coord[1]][variable])
+      }
+    }.bind(this))
+    return this._combineHistograms(histogramParts)
+  },
+  _transfromHistogram:function(hist,zoom){
+    var new_hist= {
+      bins: {},
+      bounds: hist.bounds,
+      zoom : zoom,
+      x: 0
+    }
+    var zoom_diff  = zoom - hist.zoom;
+    new_hist.x = hist.x >> zoom_diff;
+    for( var k in hist.bins){
+      var idx = (hist.x + k ) >> (zoom_diff - new_hist.x)
+      new_hist.bins[idx] = new_hist.bins[idx] ||  0
+      new_hist.bins[idx] += hist.bins[k]
+    }
+    return new_hist
+  },
+  _combineHistograms:function(histograms){
+    var minZoom = Math.min.apply(null,histograms.map(function(h){return h.zoom}))
+    var mappedHistograms = histograms.map(function(h){return this._transfromHistogram(h,minZoom)}.bind(this))
+
+    var combinedHistogram = {
+      bins:{},
+      bounds: [
+        Math.min.apply(null,mappedHistograms.map(function(h){return h.bounds[0]})),
+        Math.max.apply(null,mappedHistograms.map(function(h){return h.bounds[1]}))
+      ],
+      zoom: minZoom,
+      x: 0
+    }
+
+    mappedHistograms.forEach(function(histogram){
+      Object.keys(histogram.bins).forEach(function(bin){
+        combinedHistogram.bins[bin] = combinedHistogram.bins[bin]  || 0
+        combinedHistogram.bins[bin]+= histogram.bins[bin]
+      })
+    })
+
+
+    return combinedHistogram
+  },
   _clearTileCaches: function() {
     var t, tile;
     for(t in this._tiles) {
@@ -332,6 +397,11 @@ L.TorqueLayer = L.CanvasLayer.extend({
     return this.provider.getKeySpan();
   },
 
+  setQueryFilter:function(variable, start,end){
+    this.provider.setFilter(variable,start,end)
+
+  },
+
   /**
    * set the cartocss for the current renderer
    */