base to support chtml output in mathjax v3

Author: archmoj

src/lib/svg_text_utils.js

@@ -71,7 +71,11 @@ exports.convertToTspans = function(_context, gd, _callback) {
                 parent.selectAll('svg.' + svgClass).remove();
                 parent.selectAll('g.' + svgClass + '-group').remove();
 
-                var newSvg = _svgEl && _svgEl.select('svg');
+                var newSvg = _svgEl && _svgEl.select(
+                    v3Chtml() ?
+                        'mjx-math' :
+                        'svg'
+                );
                 if(!newSvg || !newSvg.node()) {
                     showText();
                     resolve();
@@ -165,6 +169,15 @@ exports.convertToTspans = function(_context, gd, _callback) {
 
 // MathJax
 
+function v3Chtml() {
+    return (
+        MathJax &&
+        MathJax.config &&
+        MathJax.config.startup &&
+        MathJax.config.startup.output === 'chtml'
+    );
+}
+
 var LT_MATCH = /(<|&lt;|&#60;)/g;
 var GT_MATCH = /(>|&gt;|&#62;)/g;
 
@@ -236,16 +249,21 @@ function texToSVG(_texString, _config, _callback) {
             MathJaxVersion < 3 ? '.MathJax_SVG' : '.MathJax'
         );
 
-        var node = !sel.empty() && tmpDiv.select('svg').node();
+        var node = !sel.empty() && (
+            v3Chtml() ?
+                tmpDiv.select('mjx-math').node() : // TODO: handle non-svg element in texToSVG callback!
+                tmpDiv.select('svg').node()
+        );
+
         if(!node) {
             Lib.log('There was an error in the tex syntax.', _texString);
             _callback();
         } else {
-            var svgBBox = node.getBoundingClientRect();
+            var nodeBBox = node.getBoundingClientRect();
             var glyphDefs = d3.select('body').select(
                 MathJaxVersion < 3 ? '#MathJax_SVG_glyphs' : 'defs'
             );
-            _callback(sel, glyphDefs, svgBBox);
+            _callback(sel, glyphDefs, nodeBBox);
         }
 
         tmpDiv.remove();