standardize the extra we add to contours to avoid rounding errors

this avoids an edge case where the colorbar and the colorscale got
out of sync or did not end at the same place

Author: alexcjohnson

src/traces/contour/colorbar.js

@@ -13,6 +13,7 @@ var Plots = require('../../plots/plots');
 var drawColorbar = require('../../components/colorbar/draw');
 
 var makeColorMap = require('./make_color_map');
+var endPlus = require('./end_plus');
 
 
 module.exports = function colorbar(gd, cd) {
@@ -52,7 +53,7 @@ module.exports = function colorbar(gd, cd) {
         })
         .levels({
             start: contours.start,
-            end: contours.end,
+            end: endPlus(contours),
             size: cs
         })
         .options(trace.colorbar)();

src/traces/contour/end_plus.js

@@ -0,0 +1,18 @@
+/**
+* Copyright 2012-2017, Plotly, Inc.
+* All rights reserved.
+*
+* This source code is licensed under the MIT license found in the
+* LICENSE file in the root directory of this source tree.
+*/
+
+
+'use strict';
+
+/*
+ * tiny helper to move the end of the contours a little to prevent
+ * losing the last contour to rounding errors
+ */
+module.exports = function endPlus(contours) {
+    return contours.end + contours.size / 1e6;
+};

src/traces/contour/make_color_map.js

@@ -11,13 +11,14 @@
 
 var d3 = require('d3');
 var Colorscale = require('../../components/colorscale');
+var endPlus = require('./end_plus');
 
 module.exports = function makeColorMap(trace) {
     var contours = trace.contours,
         start = contours.start,
-        end = contours.end,
+        end = endPlus(contours),
         cs = contours.size || 1,
-        nc = Math.floor((end + cs / 10 - start) / cs) + 1,
+        nc = Math.floor((end - start) / cs) + 1,
         extra = contours.coloring === 'lines' ? 0 : 1;
 
     var scl = trace.colorscale,

src/traces/contour/plot.js

@@ -17,6 +17,7 @@ var Drawing = require('../../components/drawing');
 var heatmapPlot = require('../heatmap/plot');
 var makeCrossings = require('./make_crossings');
 var findAllPaths = require('./find_all_paths');
+var endPlus = require('./end_plus');
 
 
 module.exports = function plot(gd, plotinfo, cdcontours) {
@@ -81,9 +82,10 @@ function plotOne(gd, plotinfo, cd) {
 
 function emptyPathinfo(contours, plotinfo, cd0) {
     var cs = contours.size,
-        pathinfo = [];
+        pathinfo = [],
+        end = endPlus(contours);
 
-    for(var ci = contours.start; ci < contours.end + cs / 10; ci += cs) {
+    for(var ci = contours.start; ci < end; ci += cs) {
         pathinfo.push({
             level: ci,
             // all the cells with nontrivial marching index

src/traces/contour/style.js

@@ -34,11 +34,11 @@ module.exports = function style(gd) {
 
         var colorMap = makeColorMap(trace);
 
-        c.selectAll('g.contourlevel').each(function(d, i) {
+        c.selectAll('g.contourlevel').each(function(d) {
             d3.select(this).selectAll('path')
                 .call(Drawing.lineGroupStyle,
                     line.width,
-                    contours.coloring === 'lines' ? colorMap(start + i * cs) : line.color,
+                    contours.coloring === 'lines' ? colorMap(d.level) : line.color,
                     line.dash);
         });