[poc] add 'nancolor' to heatmap

Author: etpinard

src/plot_api/plot_api.js

@@ -1314,7 +1314,7 @@ function _restyle(gd, aobj, _traces) {
     // objects need to be made) but not a recalc
     var replotAttrs = [
         'zmin', 'zmax', 'zauto',
-        'xgap', 'ygap',
+        'xgap', 'ygap', 'nancolor',
         'marker.cmin', 'marker.cmax', 'marker.cauto',
         'line.cmin', 'line.cmax',
         'marker.line.cmin', 'marker.line.cmax',

src/traces/heatmap/attributes.js

@@ -90,6 +90,13 @@ module.exports = extendFlat({}, {
         role: 'style',
         description: 'Sets the vertical gap (in pixels) between bricks.'
     },
+    nancolor: {
+        valType: 'color',
+        dflt: 'rgba(0,0,0,0)',
+        role: 'style',
+        description: 'Sets the color associated with NaN values in `z`.'
+
+    }
 },
     colorscaleAttrs,
     { autocolorscale: extendFlat({}, colorscaleAttrs.autocolorscale, {dflt: false}) },

src/traces/heatmap/defaults.js

@@ -29,6 +29,7 @@ module.exports = function supplyDefaults(traceIn, traceOut, defaultColor, layout
     }
 
     coerce('text');
+    coerce('nancolor');
 
     var zsmooth = coerce('zsmooth');
     if(zsmooth === false) {

src/traces/heatmap/plot.js

@@ -282,20 +282,23 @@ function plotOne(gd, plotinfo, cd) {
         return padding;
     }
 
+    var nanTc = tinycolor(trace.nancolor).toRgb(),
+        nanColor = [nanTc.r, nanTc.g, nanTc.b, nanTc.a];
+
     function setColor(v, pixsize) {
-        if(v !== undefined) {
-            var c = sclFunc(v);
-            c[0] = Math.round(c[0]);
-            c[1] = Math.round(c[1]);
-            c[2] = Math.round(c[2]);
-
-            pixcount += pixsize;
-            rcount += c[0] * pixsize;
-            gcount += c[1] * pixsize;
-            bcount += c[2] * pixsize;
-            return c;
-        }
-        return [0, 0, 0, 0];
+        pixcount += pixsize;
+
+        var c = v !== undefined ? sclFunc(v) : nanColor;
+
+        c[0] = Math.round(c[0]);
+        c[1] = Math.round(c[1]);
+        c[2] = Math.round(c[2]);
+
+        rcount += c[0] * pixsize;
+        gcount += c[1] * pixsize;
+        bcount += c[2] * pixsize;
+
+        return c;
     }
 
     function putColor(pixels, pxIndex, c) {