Support zooming and unzooming

stage.js

@@ -1,6 +1,7 @@
 (function() {
   var gui = require('nw.gui');
   var iframe = document.querySelector('iframe');
+  var win = gui.Window.get();
 
   var handleClick = function(e) {
     var checkForLink = function(el) {
@@ -29,18 +30,31 @@
 
     checkForLink(e.target);
   };
-
+
+  var zoom = function () { win.zoomLevel += 1; }
+  var unzoom = function () { win.zoomLevel -= 1; }
+  var resetZoom = function () { win.zoomLevel = 0; }
+
+  var handleKeydown = function (e) {
+    if (e.ctrlKey) {
+      if (e.keyCode == 187) zoom();
+      else if (e.keyCode == 189) unzoom();
+      else if (e.keyCode == 48) resetZoom();
+    }
+  };
+
   var init = function() {
     if (iframe &&
         iframe.contentWindow &&
         iframe.contentWindow.document &&
         iframe.contentWindow.document.body &&
         iframe.contentWindow.document.body.innerHTML) {
      iframe.contentWindow.document.body.addEventListener('click', handleClick, false);
+     iframe.contentWindow.document.body.addEventListener('keydown', handleKeydown, false);
     } else {
       setTimeout(init, 100);
     }
   };
-  
+
   init();
 }).apply(this);