fix hover and click selection on subplots with zorder

Author: archmoj

src/components/fx/hover.js

@@ -15,6 +15,7 @@ var Drawing = require('../drawing');
 var Color = require('../color');
 var dragElement = require('../dragelement');
 var Axes = require('../../plots/cartesian/axes');
+var zindexSeparator = require('../../plots/cartesian/constants').zindexSeparator;
 var Registry = require('../../registry');
 
 var helpers = require('./helpers');
@@ -261,6 +262,11 @@ exports.loneHover = function loneHover(hoverItems, opts) {
 function _hover(gd, evt, subplot, noHoverEvent, eventTarget) {
     if(!subplot) subplot = 'xy';
 
+    if(typeof subplot === 'string') {
+        // drop zindex from subplot id
+        subplot = subplot.split(zindexSeparator)[0];
+    }
+
     // if the user passed in an array of subplots,
     // use those instead of finding overlayed plots
     var subplots = Array.isArray(subplot) ? subplot : [subplot];