add option to enable legends for

- choropleth
- choroplethmapbox
- cone
- densitymapbox
- heatmap
- histogram2d
- isosurface
- mesh3d
- streamtube
- surface
- volume

src/components/legend/defaults.js

@@ -33,7 +33,14 @@ module.exports = function legendDefaults(layoutIn, layoutOut, fullData) {
         // *would* be shown by default, toward the two traces you need to
         // ensure the legend is shown by default, because this can still help
         // disambiguate.
-        if(trace.showlegend || trace._dfltShowLegend) {
+        if(trace.showlegend || (
+            trace._dfltShowLegend && !(
+                trace._module &&
+                trace._module.attributes &&
+                trace._module.attributes.showlegend &&
+                trace._module.attributes.showlegend.dflt === false
+            )
+        )) {
             legendTraceCount++;
             if(trace.showlegend) {
                 legendReallyHasATrace = true;

src/components/legend/style.js

@@ -84,6 +84,7 @@ module.exports = function style(s, gd) {
           .enter().append('g')
             .classed('legendpoints', true);
     })
+    .each(styleSpatial)
     .each(styleWaterfalls)
     .each(styleFunnels)
     .each(styleBars)
@@ -481,6 +482,124 @@ module.exports = function style(s, gd) {
             stylePie(pts, d0Mod, tMod);
         }
     }
+
+    function styleSpatial(d) { // i.e. maninly traces having z and colorscale
+        var trace = d[0].trace;
+
+        var useGradient;
+        var ptsData = [];
+        if(trace.visible) {
+            switch(trace.type) {
+                case 'histogram2d' :
+                case 'heatmap' :
+                    ptsData = [
+                        ['M-15,-2V4H15V-2Z'] // similar to contour
+                    ];
+                    useGradient = true;
+                    break;
+                case 'choropleth' :
+                case 'choroplethmapbox' :
+                case 'densitymapbox' :
+                    ptsData = [
+                        ['M-6,-6V6H6V-6Z']
+                    ];
+                    useGradient = true;
+                    break;
+                case 'cone' :
+                    ptsData = [
+                        ['M-6,2 A2,2 0 0,0 -6,6 V6L6,4Z'],
+                        ['M-6,-6 A2,2 0 0,0 -6,-2 L6,-4Z'],
+                        ['M-6,-2 A2,2 0 0,0 -6,2 L6,0Z']
+                    ];
+                    useGradient = false;
+                    break;
+                case 'streamtube' :
+                    ptsData = [
+                        ['M-6,2 A2,2 0 0,0 -6,6 H6 A2,2 0 0,1 6,2 Z'],
+                        ['M-6,-6 A2,2 0 0,0 -6,-2 H6 A2,2 0 0,1 6,-6 Z'],
+                        ['M-6,-2 A2,2 0 0,0 -6,2 H6 A2,2 0 0,1 6,-2 Z']
+                    ];
+                    useGradient = false;
+                    break;
+                case 'surface' :
+                    ptsData = [
+                        ['M-6,-6 A2,3 0 0,0 -6,0 H6 A2,3 0 0,1 6,-6 Z'],
+                        ['M-6,1 A2,3 0 0,1 -6,6 H6 A2,3 0 0,0 6,0 Z']
+                    ];
+                    useGradient = true;
+                    break;
+                case 'mesh3d' :
+                    ptsData = [
+                        ['M-6,6H0L-6,-6Z'],
+                        ['M6,6H0L6,-6Z'],
+                        ['M-6,-6H6L0,6Z']
+                    ];
+                    useGradient = false;
+                    break;
+                case 'volume' :
+                    ptsData = [
+                        ['M-6,6H0L-6,-6Z'],
+                        ['M6,6H0L6,-6Z'],
+                        ['M-6,-6H6L0,6Z']
+                    ];
+                    useGradient = true;
+                    break;
+                case 'isosurface':
+                    ptsData = [
+                        ['M-6,6H0L-6,-6Z'],
+                        ['M6,6H0L6,-6Z'],
+                        ['M-6,-6 A12,24 0 0,0 6,-6 L0,6Z']
+                    ];
+                    useGradient = false;
+                    break;
+            }
+        }
+
+        var pts = d3.select(this).select('g.legendpoints')
+            .selectAll('path.legend3dandfriends')
+            .data(ptsData);
+        pts.enter().append('path').classed('legend3dandfriends', true)
+            .attr('transform', 'translate(20,0)')
+            .style('stroke-miterlimit', 1);
+        pts.exit().remove();
+
+        pts.each(function(dd, i) {
+            var pt = d3.select(this);
+
+            var cOpts = extractOpts(trace);
+            var colorscale = cOpts.colorscale;
+            var reversescale = cOpts.reversescale;
+            var fillGradient = function(s) {
+                if(s.size()) {
+                    var gradientID = 'legendfill-' + trace.uid;
+                    Drawing.gradient(s, gd, gradientID,
+                        reversescale ? 'horizontal' : 'horizontalreversed',
+                        colorscale, 'fill');
+                }
+            };
+
+            var fillColor;
+            if(!colorscale) {
+                var color = trace.vertexcolor || trace.facecolor || trace.color;
+                fillColor = Lib.isArrayOrTypedArray(color) ? (color[i] || color[0]) : color;
+            } else {
+                if(!useGradient) {
+                    var len = colorscale.length;
+                    fillColor =
+                        i === 0 ? colorscale[reversescale ? len - 1 : 0][1] : // minimum
+                        i === 1 ? colorscale[reversescale ? 0 : len - 1][1] : // maximum
+                            colorscale[Math.floor((len - 1) / 2)][1]; // middle
+                }
+            }
+
+            pt.attr('d', dd[0]);
+            if(fillColor) {
+                pt.call(Color.fill, fillColor);
+            } else {
+                pt.call(fillGradient);
+            }
+        });
+    }
 };
 
 function getGradientDirection(reversescale) {

src/plots/plots.js

@@ -1291,9 +1291,16 @@ plots.supplyTraceDefaults = function(traceIn, traceOut, colorIndex, layout, trac
         coerce('meta');
 
         if(Registry.traceIs(traceOut, 'showLegend')) {
-            traceOut._dfltShowLegend = true;
-            coerce('showlegend');
+            Lib.coerce(traceIn, traceOut,
+                _module.attributes.showlegend ?
+                _module.attributes :
+                plots.attributes,
+                'showlegend'
+            );
+
             coerce('legendgroup');
+
+            traceOut._dfltShowLegend = true;
         } else {
             traceOut._dfltShowLegend = false;
         }

src/traces/choropleth/attributes.js

@@ -77,7 +77,8 @@ module.exports = extendFlat({
         editType: 'calc',
         flags: ['location', 'z', 'text', 'name']
     }),
-    hovertemplate: hovertemplateAttrs()
+    hovertemplate: hovertemplateAttrs(),
+    showlegend: extendFlat({}, baseAttrs.showlegend, {dflt: false})
 },
 
     colorScaleAttrs('', {

src/traces/choropleth/index.js

@@ -23,7 +23,7 @@ module.exports = {
     moduleType: 'trace',
     name: 'choropleth',
     basePlotModule: require('../../plots/geo'),
-    categories: ['geo', 'noOpacity'],
+    categories: ['geo', 'noOpacity', 'showLegend'],
     meta: {
         description: [
             'The data that describes the choropleth value-to-color mapping',

src/traces/choroplethmapbox/attributes.js

@@ -11,7 +11,7 @@
 var choroplethAttrs = require('../choropleth/attributes');
 var colorScaleAttrs = require('../../components/colorscale/attributes');
 var hovertemplateAttrs = require('../../plots/template_attributes').hovertemplateAttrs;
-
+var baseAttrs = require('../../plots/attributes');
 var extendFlat = require('../../lib/extend').extendFlat;
 
 module.exports = extendFlat({
@@ -103,7 +103,8 @@ module.exports = extendFlat({
     },
 
     hoverinfo: choroplethAttrs.hoverinfo,
-    hovertemplate: hovertemplateAttrs({}, {keys: ['properties']})
+    hovertemplate: hovertemplateAttrs({}, {keys: ['properties']}),
+    showlegend: extendFlat({}, baseAttrs.showlegend, {dflt: false})
 },
 
     colorScaleAttrs('', {

src/traces/choroplethmapbox/index.js

@@ -52,7 +52,7 @@ module.exports = {
     moduleType: 'trace',
     name: 'choroplethmapbox',
     basePlotModule: require('../../plots/mapbox'),
-    categories: ['mapbox', 'gl', 'noOpacity'],
+    categories: ['mapbox', 'gl', 'noOpacity', 'showLegend'],
     meta: {
         hr_name: 'choropleth_mapbox',
         description: [

src/traces/cone/attributes.js

@@ -166,7 +166,9 @@ var attrs = {
         editType: 'calc',
         description: 'Same as `text`.'
     },
-    hovertemplate: hovertemplateAttrs({editType: 'calc'}, {keys: ['norm']})
+
+    hovertemplate: hovertemplateAttrs({editType: 'calc'}, {keys: ['norm']}),
+    showlegend: extendFlat({}, baseAttrs.showlegend, {dflt: false})
 };
 
 extendFlat(attrs, colorScaleAttrs('', {

src/traces/cone/index.js

@@ -12,7 +12,7 @@ module.exports = {
     moduleType: 'trace',
     name: 'cone',
     basePlotModule: require('../../plots/gl3d'),
-    categories: ['gl3d'],
+    categories: ['gl3d', 'showLegend'],
 
     attributes: require('./attributes'),
     supplyDefaults: require('./defaults'),

src/traces/densitymapbox/attributes.js

@@ -84,7 +84,8 @@ module.exports = extendFlat({
     hoverinfo: extendFlat({}, baseAttrs.hoverinfo, {
         flags: ['lon', 'lat', 'z', 'text', 'name']
     }),
-    hovertemplate: hovertemplateAttrs()
+    hovertemplate: hovertemplateAttrs(),
+    showlegend: extendFlat({}, baseAttrs.showlegend, {dflt: false})
 },
     colorScaleAttrs('', {
         cLetter: 'z',

src/traces/densitymapbox/index.js

@@ -37,7 +37,7 @@ module.exports = {
     moduleType: 'trace',
     name: 'densitymapbox',
     basePlotModule: require('../../plots/mapbox'),
-    categories: ['mapbox', 'gl'],
+    categories: ['mapbox', 'gl', 'showLegend'],
     meta: {
         hr_name: 'density_mapbox',
         description: [

src/traces/heatmap/attributes.js

@@ -9,6 +9,7 @@
 'use strict';
 
 var scatterAttrs = require('../scatter/attributes');
+var baseAttrs = require('../../plots/attributes');
 var hovertemplateAttrs = require('../../plots/template_attributes').hovertemplateAttrs;
 var colorScaleAttrs = require('../../components/colorscale/attributes');
 var FORMAT_LINK = require('../../constants/docs').FORMAT_LINK;
@@ -130,7 +131,8 @@ module.exports = extendFlat({
             FORMAT_LINK
         ].join(' ')
     },
-    hovertemplate: hovertemplateAttrs()
+    hovertemplate: hovertemplateAttrs(),
+    showlegend: extendFlat({}, baseAttrs.showlegend, {dflt: false})
 }, {
     transforms: undefined
 },

src/traces/heatmap/index.js

@@ -20,7 +20,7 @@ module.exports = {
     moduleType: 'trace',
     name: 'heatmap',
     basePlotModule: require('../../plots/cartesian'),
-    categories: ['cartesian', 'svg', '2dMap'],
+    categories: ['cartesian', 'svg', '2dMap', 'showLegend'],
     meta: {
         description: [
             'The data that describes the heatmap value-to-color mapping',

src/traces/histogram2d/attributes.js

@@ -11,6 +11,7 @@
 var histogramAttrs = require('../histogram/attributes');
 var makeBinAttrs = require('../histogram/bin_attributes');
 var heatmapAttrs = require('../heatmap/attributes');
+var baseAttrs = require('../../plots/attributes');
 var hovertemplateAttrs = require('../../plots/template_attributes').hovertemplateAttrs;
 var colorScaleAttrs = require('../../components/colorscale/attributes');
 
@@ -72,7 +73,8 @@ module.exports = extendFlat(
         ygap: heatmapAttrs.ygap,
         zsmooth: heatmapAttrs.zsmooth,
         zhoverformat: heatmapAttrs.zhoverformat,
-        hovertemplate: hovertemplateAttrs({}, {keys: 'z'})
+        hovertemplate: hovertemplateAttrs({}, {keys: 'z'}),
+        showlegend: extendFlat({}, baseAttrs.showlegend, {dflt: false})
     },
     colorScaleAttrs('', {cLetter: 'z', autoColorDflt: false})
 );

src/traces/histogram2d/index.js

@@ -9,7 +9,6 @@
 'use strict';
 
 module.exports = {
-
     attributes: require('./attributes'),
     supplyDefaults: require('./defaults'),
     crossTraceDefaults: require('../histogram/cross_trace_defaults'),
@@ -24,7 +23,7 @@ module.exports = {
     moduleType: 'trace',
     name: 'histogram2d',
     basePlotModule: require('../../plots/cartesian'),
-    categories: ['cartesian', 'svg', '2dMap', 'histogram'],
+    categories: ['cartesian', 'svg', '2dMap', 'histogram', 'showLegend'],
     meta: {
         hrName: 'histogram_2d',
         description: [

src/traces/isosurface/attributes.js

@@ -232,7 +232,8 @@ var attrs = module.exports = overrideAll(extendFlat({
         arrayOk: true,
         description: 'Same as `text`.'
     },
-    hovertemplate: hovertemplateAttrs()
+    hovertemplate: hovertemplateAttrs(),
+    showlegend: extendFlat({}, baseAttrs.showlegend, {dflt: false})
 },
 
 colorScaleAttrs('', {

src/traces/isosurface/index.js

@@ -21,7 +21,7 @@ module.exports = {
     moduleType: 'trace',
     name: 'isosurface',
     basePlotModule: require('../../plots/gl3d'),
-    categories: ['gl3d'],
+    categories: ['gl3d', 'showLegend'],
     meta: {
         description: [
             'Draws isosurfaces between iso-min and iso-max values with coordinates given by',

src/traces/mesh3d/attributes.js

@@ -238,5 +238,6 @@ colorScaleAttrs('', {
         editType: 'calc'
     }, surfaceAttrs.lighting),
 
-    hoverinfo: extendFlat({}, baseAttrs.hoverinfo, {editType: 'calc'})
+    hoverinfo: extendFlat({}, baseAttrs.hoverinfo, {editType: 'calc'}),
+    showlegend: extendFlat({}, baseAttrs.showlegend, {dflt: false})
 });

src/traces/mesh3d/index.js

@@ -21,7 +21,7 @@ module.exports = {
     moduleType: 'trace',
     name: 'mesh3d',
     basePlotModule: require('../../plots/gl3d'),
-    categories: ['gl3d'],
+    categories: ['gl3d', 'showLegend'],
     meta: {
         description: [
             'Draws sets of triangles with coordinates given by',

src/traces/streamtube/attributes.js

@@ -144,7 +144,8 @@ var attrs = {
             'tubeu', 'tubev', 'tubew',
             'norm', 'divergence'
         ]
-    })
+    }),
+    showlegend: extendFlat({}, baseAttrs.showlegend, {dflt: false})
 };
 
 extendFlat(attrs, colorScaleAttrs('', {

src/traces/streamtube/index.js

@@ -12,7 +12,7 @@ module.exports = {
     moduleType: 'trace',
     name: 'streamtube',
     basePlotModule: require('../../plots/gl3d'),
-    categories: ['gl3d'],
+    categories: ['gl3d', 'showLegend'],
 
     attributes: require('./attributes'),
     supplyDefaults: require('./defaults'),

src/traces/surface/attributes.js

@@ -310,7 +310,8 @@ colorScaleAttrs('', {
         })
     },
 
-    hoverinfo: extendFlat({}, baseAttrs.hoverinfo)
+    hoverinfo: extendFlat({}, baseAttrs.hoverinfo),
+    showlegend: extendFlat({}, baseAttrs.showlegend, {dflt: false}),
 }), 'calc', 'nested');
 
 attrs.x.editType = attrs.y.editType = attrs.z.editType = 'calc+clearAxisTypes';

src/traces/surface/index.js

@@ -21,7 +21,7 @@ module.exports = {
     moduleType: 'trace',
     name: 'surface',
     basePlotModule: require('../../plots/gl3d'),
-    categories: ['gl3d', '2dMap'],
+    categories: ['gl3d', '2dMap', 'showLegend'],
     meta: {
         description: [
             'The data the describes the coordinates of the surface is set in `z`.',

src/traces/volume/attributes.js

@@ -86,7 +86,8 @@ colorScaleAttrs('', {
     flatshading: isosurfaceAttrs.flatshading,
     contour: isosurfaceAttrs.contour,
 
-    hoverinfo: extendFlat({}, baseAttrs.hoverinfo)
+    hoverinfo: extendFlat({}, baseAttrs.hoverinfo),
+    showlegend: extendFlat({}, baseAttrs.showlegend, {dflt: false})
 }), 'calc', 'nested');
 
 attrs.x.editType = attrs.y.editType = attrs.z.editType = attrs.value.editType = 'calc+clearAxisTypes';