Add pause and play events to autoplay (#713)

This is useful to request pause/resume from other plugins

js/impress.js

@@ -1304,6 +1304,16 @@
         // triggered for the first slide, so that's where code flow continues.
     }, false );
 
+    document.addEventListener( "impress:autoplay:pause", function( event ) {
+        status = "paused";
+        reloadTimeout( event );
+    }, false );
+
+    document.addEventListener( "impress:autoplay:play", function( event ) {
+        status = "playing";
+        reloadTimeout( event );
+    }, false );
+
     // If default autoplay time was defined in the presentation root, or
     // in this step, set timeout.
     var reloadTimeout = function( event ) {
@@ -1342,13 +1352,6 @@
     var status = "not clicked";
     var toolbarButton = null;
 
-    // Copied from core impress.js. Good candidate for moving to a utilities collection.
-    var triggerEvent = function( el, eventName, detail ) {
-        var event = document.createEvent( "CustomEvent" );
-        event.initCustomEvent( eventName, true, true, detail );
-        el.dispatchEvent( event );
-    };
-
     var makeDomElement = function( html ) {
         var tempDiv = document.createElement( "div" );
         tempDiv.innerHTML = html;
@@ -1407,7 +1410,7 @@
             }
         } );
 
-        triggerEvent( toolbar, "impress:toolbar:appendChild",
+        util.triggerEvent( toolbar, "impress:toolbar:appendChild",
                       { group: 10, element: toolbarButton } );
     };