use fullLayout._gradientUrlQueryParts stash to fix gradient URLs

... during image exports, instead of having hard-coded list
    of query-selectors in toSVG routine.

Author: etpinard

src/components/drawing/index.js

@@ -300,9 +300,10 @@ drawing.gradient = function(sel, gd, gradientID, type, colorscale, prop) {
         }
     }
 
-    var fullID = 'g' + gd._fullLayout._uid + '-' + gradientID;
+    var fullLayout = gd._fullLayout;
+    var fullID = 'g' + fullLayout._uid + '-' + gradientID;
 
-    var gradient = gd._fullLayout._defs.select('.gradients')
+    var gradient = fullLayout._defs.select('.gradients')
         .selectAll('#' + fullID)
         .data([type + colorStops.join(';')], Lib.identity);
 
@@ -333,6 +334,13 @@ drawing.gradient = function(sel, gd, gradientID, type, colorscale, prop) {
 
     sel.style(prop, getFullUrl(fullID, gd))
         .style(prop + '-opacity', null);
+
+    var className2query = function(s) {
+        return '.' + s.attr('class').replace(/\s/g, '.');
+    };
+    var k = className2query(d3.select(sel.node().parentNode)) +
+        '>' + className2query(sel);
+    fullLayout._gradientUrlQueryParts[k] = 1;
 };
 
 /*
@@ -343,8 +351,14 @@ drawing.gradient = function(sel, gd, gradientID, type, colorscale, prop) {
  * The upside of this is arbitrary points can share gradient defs
  */
 drawing.initGradients = function(gd) {
-    var gradientsGroup = Lib.ensureSingle(gd._fullLayout._defs, 'g', 'gradients');
+    var fullLayout = gd._fullLayout;
+
+    var gradientsGroup = Lib.ensureSingle(fullLayout._defs, 'g', 'gradients');
     gradientsGroup.selectAll('linearGradient,radialGradient').remove();
+
+    // initialize stash of query parts filled in Drawing.gradient,
+    // used to fix URL strings during image exports
+    fullLayout._gradientUrlQueryParts = {};
 };
 
 

src/snapshot/tosvg.js

@@ -115,21 +115,29 @@ module.exports = function toSVG(gd, format, scale) {
             }
         });
 
-    svg.selectAll('.point, .scatterpts, .legendfill>path, .legendlines>path, path.legend3dandfriends, .cbfill').each(function() {
-        var pt = d3.select(this);
-
-        // similar to font family styles above,
-        // we must remove " after the SVG DOM has been serialized
-        var fill = this.style.fill;
-        if(fill && fill.indexOf('url(') !== -1) {
-            pt.style('fill', fill.replace(DOUBLEQUOTE_REGEX, DUMMY_SUB));
-        }
 
-        var stroke = this.style.stroke;
-        if(stroke && stroke.indexOf('url(') !== -1) {
-            pt.style('stroke', stroke.replace(DOUBLEQUOTE_REGEX, DUMMY_SUB));
+    if(fullLayout._gradientUrlQueryParts) {
+        var queryParts = [];
+        for(var k in fullLayout._gradientUrlQueryParts) queryParts.push(k);
+
+        if(queryParts.length) {
+            svg.selectAll(queryParts.join(',')).each(function() {
+                var pt = d3.select(this);
+
+                // similar to font family styles above,
+                // we must remove " after the SVG DOM has been serialized
+                var fill = this.style.fill;
+                if(fill && fill.indexOf('url(') !== -1) {
+                    pt.style('fill', fill.replace(DOUBLEQUOTE_REGEX, DUMMY_SUB));
+                }
+
+                var stroke = this.style.stroke;
+                if(stroke && stroke.indexOf('url(') !== -1) {
+                    pt.style('stroke', stroke.replace(DOUBLEQUOTE_REGEX, DUMMY_SUB));
+                }
+            });
         }
-    });
+    }
 
     if(format === 'pdf' || format === 'eps') {
         // these formats make the extra line MathJax adds around symbols look super thick in some cases