Contour legend

src/components/drawing/index.js

@@ -266,43 +266,76 @@ function makePointPath(symbolNumber, r) {
 
 var HORZGRADIENT = {x1: 1, x2: 0, y1: 0, y2: 0};
 var VERTGRADIENT = {x1: 0, x2: 0, y1: 1, y2: 0};
+var stopFormatter = d3.format('~.1f');
+var gradientInfo = {
+    radial: {node: 'radialGradient'},
+    radialreversed: {node: 'radialGradient', reversed: true},
+    horizontal: {node: 'linearGradient', attrs: HORZGRADIENT},
+    horizontalreversed: {node: 'linearGradient', attrs: HORZGRADIENT, reversed: true},
+    vertical: {node: 'linearGradient', attrs: VERTGRADIENT},
+    verticalreversed: {node: 'linearGradient', attrs: VERTGRADIENT, reversed: true}
+};
+
+/**
+ * gradient: create and apply a gradient fill
+ *
+ * @param {object} sel: d3 selection to apply this gradient to
+ *     You can use `selection.call(Drawing.gradient, ...)`
+ * @param {DOM element} gd: the graph div `sel` is part of
+ * @param {string} gradientID: a unique (within this plot) identifier
+ *     for this gradient, so that we don't create unnecessary definitions
+ * @param {string} type: 'radial', 'horizontal', or 'vertical', optionally with
+ *     'reversed' at the end. Normally radial goes center to edge,
+ *     horizontal goes right to left, and vertical goes bottom to top
+ * @param {array} colorscale: as in attribute values, [[fraction, color], ...]
+ * @param {string} prop: the property to apply to, 'fill' or 'stroke'
+ */
+drawing.gradient = function(sel, gd, gradientID, type, colorscale, prop) {
+    var len = colorscale.length;
+    var info = gradientInfo[type];
+    var colorStops = new Array(len);
+    for(var i = 0; i < len; i++) {
+        if(info.reversed) {
+            colorStops[len - 1 - i] = [stopFormatter((1 - colorscale[i][0]) * 100), colorscale[i][1]];
+        }
+        else {
+            colorStops[i] = [stopFormatter(colorscale[i][0] * 100), colorscale[i][1]];
+        }
+    }
+
+    var fullID = 'g' + gd._fullLayout._uid + '-' + gradientID;
 
-drawing.gradient = function(sel, gd, gradientID, type, color1, color2) {
     var gradient = gd._fullLayout._defs.select('.gradients')
-        .selectAll('#' + gradientID)
-        .data([type + color1 + color2], Lib.identity);
+        .selectAll('#' + fullID)
+        .data([type + colorStops.join(';')], Lib.identity);
 
     gradient.exit().remove();
 
     gradient.enter()
-        .append(type === 'radial' ? 'radialGradient' : 'linearGradient')
+        .append(info.node)
         .each(function() {
             var el = d3.select(this);
-            if(type === 'horizontal') el.attr(HORZGRADIENT);
-            else if(type === 'vertical') el.attr(VERTGRADIENT);
-
-            el.attr('id', gradientID);
-
-            var tc1 = tinycolor(color1);
-            var tc2 = tinycolor(color2);
-
-            el.append('stop').attr({
-                offset: '0%',
-                'stop-color': Color.tinyRGB(tc2),
-                'stop-opacity': tc2.getAlpha()
-            });
-
-            el.append('stop').attr({
-                offset: '100%',
-                'stop-color': Color.tinyRGB(tc1),
-                'stop-opacity': tc1.getAlpha()
+            if(info.attrs) el.attr(info.attrs);
+
+            el.attr('id', fullID);
+
+            var stops = el.selectAll('stop')
+                .data(colorStops);
+            stops.exit().remove();
+            stops.enter().append('stop');
+
+            stops.each(function(d) {
+                var tc = tinycolor(d[1]);
+                d3.select(this).attr({
+                    offset: d[0] + '%',
+                    'stop-color': Color.tinyRGB(tc),
+                    'stop-opacity': tc.getAlpha()
+                });
             });
         });
 
-    sel.style({
-        fill: 'url(#' + gradientID + ')',
-        'fill-opacity': null
-    });
+    sel.style(prop, 'url(#' + fullID + ')')
+        .style(prop + '-opacity', null);
 };
 
 /*
@@ -420,21 +453,29 @@ drawing.singlePointStyle = function(d, sel, trace, fns, gd) {
         if(gradientType) perPointGradient = true;
         else gradientType = markerGradient && markerGradient.type;
 
+        // for legend - arrays will propagate through here, but we don't need
+        // to treat it as per-point.
+        if(Array.isArray(gradientType)) {
+            gradientType = gradientType[0];
+            if(!gradientInfo[gradientType]) gradientType = 0;
+        }
+
         if(gradientType && gradientType !== 'none') {
             var gradientColor = d.mgc;
             if(gradientColor) perPointGradient = true;
             else gradientColor = markerGradient.color;
 
-            var gradientID = 'g' + gd._fullLayout._uid + '-' + trace.uid;
+            var gradientID = trace.uid;
             if(perPointGradient) gradientID += '-' + d.i;
 
-            sel.call(drawing.gradient, gd, gradientID, gradientType, fillColor, gradientColor);
+            drawing.gradient(sel, gd, gradientID, gradientType,
+                [[0, gradientColor], [1, fillColor]], 'fill');
         } else {
-            sel.call(Color.fill, fillColor);
+            Color.fill(sel, fillColor);
         }
 
         if(lineWidth) {
-            sel.call(Color.stroke, lineColor);
+            Color.stroke(sel, lineColor);
         }
     }
 };

src/components/legend/defaults.js

@@ -21,18 +21,33 @@ var helpers = require('./helpers');
 module.exports = function legendDefaults(layoutIn, layoutOut, fullData) {
     var containerIn = layoutIn.legend || {};
 
-    var visibleTraces = 0;
+    var legendTraceCount = 0;
+    var legendReallyHasATrace = false;
     var defaultOrder = 'normal';
 
     var defaultX, defaultY, defaultXAnchor, defaultYAnchor;
 
     for(var i = 0; i < fullData.length; i++) {
         var trace = fullData[i];
 
-        if(helpers.legendGetsTrace(trace)) {
-            visibleTraces++;
-            // always show the legend by default if there's a pie
-            if(Registry.traceIs(trace, 'pie')) visibleTraces++;
+        if(!trace.visible) continue;
+
+        // Note that we explicitly count any trace that is either shown or
+        // *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) {
+            legendTraceCount++;
+            if(trace.showlegend) {
+                legendReallyHasATrace = true;
+                // Always show the legend by default if there's a pie,
+                // or if there's only one trace but it's explicitly shown
+                if(Registry.traceIs(trace, 'pie') ||
+                    trace._input.showlegend === true
+                ) {
+                    legendTraceCount++;
+                }
+            }
         }
 
         if((Registry.traceIs(trace, 'bar') && layoutOut.barmode === 'stack') ||
@@ -48,7 +63,8 @@ module.exports = function legendDefaults(layoutIn, layoutOut, fullData) {
     }
 
     var showLegend = Lib.coerce(layoutIn, layoutOut,
-        basePlotLayoutAttributes, 'showlegend', visibleTraces > 1);
+        basePlotLayoutAttributes, 'showlegend',
+        legendReallyHasATrace && legendTraceCount > 1);
 
     if(showLegend === false) return;
 

src/components/legend/get_legend_data.js

@@ -41,12 +41,12 @@ module.exports = function getLegendData(calcdata, opts) {
 
     // build an { legendgroup: [cd0, cd0], ... } object
     for(i = 0; i < calcdata.length; i++) {
-        var cd = calcdata[i],
-            cd0 = cd[0],
-            trace = cd0.trace,
-            lgroup = trace.legendgroup;
+        var cd = calcdata[i];
+        var cd0 = cd[0];
+        var trace = cd0.trace;
+        var lgroup = trace.legendgroup;
 
-        if(!helpers.legendGetsTrace(trace) || !trace.showlegend) continue;
+        if(!trace.visible || !trace.showlegend) continue;
 
         if(Registry.traceIs(trace, 'pie')) {
             if(!slicesShown[lgroup]) slicesShown[lgroup] = {};

src/components/legend/helpers.js

@@ -9,16 +9,6 @@
 
 'use strict';
 
-exports.legendGetsTrace = function legendGetsTrace(trace) {
-    // traceIs(trace, 'showLegend') is not sufficient anymore, due to contour(carpet)?
-    // which are legend-eligible only if type: constraint. Otherwise, showlegend gets deleted.
-
-    // Note that we explicitly include showlegend: false, so a trace that *could* be
-    // in the legend but is not shown still counts toward the two traces you need to
-    // ensure the legend is shown by default, because this can still help disambiguate.
-    return trace.visible && (trace.showlegend !== undefined);
-};
-
 exports.isGrouped = function isGrouped(legendLayout) {
     return (legendLayout.traceorder || '').indexOf('grouped') !== -1;
 };

src/components/legend/style.js

@@ -61,25 +61,78 @@ module.exports = function style(s, gd) {
         var showFill = trace.visible && trace.fill && trace.fill !== 'none';
         var showLine = subTypes.hasLines(trace);
         var contours = trace.contours;
+        var showGradientLine = false;
+        var showGradientFill = false;
 
-        if(contours && contours.type === 'constraint') {
-            showLine = contours.showlines;
-            showFill = contours._operation !== '=';
+        if(contours) {
+            var coloring = contours.coloring;
+
+            if(coloring === 'lines') {
+                showGradientLine = true;
+            }
+            else {
+                showLine = coloring === 'none' || coloring === 'heatmap' ||
+                    contours.showlines;
+            }
+
+            if(contours.type === 'constraint') {
+                showFill = contours._operation !== '=';
+            }
+            else if(coloring === 'fill' || coloring === 'heatmap') {
+                showGradientFill = true;
+            }
         }
 
-        var fill = d3.select(this).select('.legendfill').selectAll('path')
-            .data(showFill ? [d] : []);
+        // with fill and no markers or text, move the line and fill up a bit
+        // so it's more centered
+        var markersOrText = subTypes.hasMarkers(trace) || subTypes.hasText(trace);
+        var anyFill = showFill || showGradientFill;
+        var anyLine = showLine || showGradientLine;
+        var pathStart = (markersOrText || !anyFill) ? 'M5,0' :
+            // with a line leave it slightly below center, to leave room for the
+            // line thickness and because the line is usually more prominent
+            anyLine ? 'M5,-2' : 'M5,-3';
+
+        var this3 = d3.select(this);
+
+        var fill = this3.select('.legendfill').selectAll('path')
+            .data(showFill || showGradientFill ? [d] : []);
         fill.enter().append('path').classed('js-fill', true);
         fill.exit().remove();
-        fill.attr('d', 'M5,0h30v6h-30z')
-            .call(Drawing.fillGroupStyle);
+        fill.attr('d', pathStart + 'h30v6h-30z')
+            .call(showFill ? Drawing.fillGroupStyle : fillGradient);
 
-        var line = d3.select(this).select('.legendlines').selectAll('path')
-            .data(showLine ? [d] : []);
-        line.enter().append('path').classed('js-line', true)
-            .attr('d', 'M5,0h30');
+        var line = this3.select('.legendlines').selectAll('path')
+            .data(showLine || showGradientLine ? [d] : []);
+        line.enter().append('path').classed('js-line', true);
         line.exit().remove();
-        line.call(Drawing.lineGroupStyle);
+
+        // this is ugly... but you can't apply a gradient to a perfectly
+        // horizontal or vertical line. Presumably because then
+        // the system doesn't know how to scale vertical variation, even
+        // though there *is* no vertical variation in this case.
+        // so add an invisibly small angle to the line
+        // This issue (and workaround) exist across (Mac) Chrome, FF, and Safari
+        line.attr('d', pathStart + (showGradientLine ? 'l30,0.0001' : 'h30'))
+            .call(showLine ? Drawing.lineGroupStyle : lineGradient);
+
+        function fillGradient(s) {
+            if(s.size()) {
+                var gradientID = 'legendfill-' + trace.uid;
+                Drawing.gradient(s, gd, gradientID, 'horizontalreversed',
+                    trace.colorscale, 'fill');
+            }
+        }
+
+        function lineGradient(s) {
+            if(s.size()) {
+                var gradientID = 'legendline-' + trace.uid;
+                Drawing.lineGroupStyle(s);
+                Drawing.gradient(s, gd, gradientID, 'horizontalreversed',
+                    trace.colorscale, 'stroke');
+            }
+        }
+
     }
 
     function stylePoints(d) {

src/plots/layout_attributes.js

@@ -173,7 +173,13 @@ module.exports = {
         valType: 'boolean',
         role: 'info',
         editType: 'legend',
-        description: 'Determines whether or not a legend is drawn.'
+        description: [
+            'Determines whether or not a legend is drawn.',
+            'Default is `true` if there is a trace to show and any of these:',
+            'a) Two or more traces would by default be shown in the legend.',
+            'b) One pie trace is shown in the legend.',
+            'c) One trace is explicitly given with `showlegend: true`.'
+        ].join(' ')
     },
     colorway: {
         valType: 'colorlist',

src/plots/plots.js

@@ -1144,9 +1144,13 @@ plots.supplyTraceDefaults = function(traceIn, traceOut, colorIndex, layout, trac
         coerce('ids');
 
         if(Registry.traceIs(traceOut, 'showLegend')) {
+            traceOut._dfltShowLegend = true;
             coerce('showlegend');
             coerce('legendgroup');
         }
+        else {
+            traceOut._dfltShowLegend = false;
+        }
 
         Registry.getComponentMethod(
             'fx',

src/traces/contour/defaults.js

@@ -37,9 +37,6 @@ module.exports = function supplyDefaults(traceIn, traceOut, defaultColor, layout
     var isConstraint = (coerce('contours.type') === 'constraint');
     coerce('connectgaps', Lib.isArray1D(traceOut.z));
 
-    // trace-level showlegend has already been set, but is only allowed if this is a constraint
-    if(!isConstraint) delete traceOut.showlegend;
-
     if(isConstraint) {
         handleConstraintDefaults(traceIn, traceOut, coerce, layout, defaultColor);
     }