diff --git a/core/modules/startup/rootwidget.js b/core/modules/startup/rootwidget.js
index f0c3bd450..0fdcfd9a2 100644
--- a/core/modules/startup/rootwidget.js
+++ b/core/modules/startup/rootwidget.js
@@ -42,10 +42,16 @@ exports.startup = function() {
 	var fullscreen = $tw.utils.getFullScreenApis();
 	if(fullscreen) {
 		$tw.rootWidget.addEventListener("tm-full-screen",function(event) {
-			if(event.event.target.ownerDocument[fullscreen._fullscreenElement]) {
+			if(event.param === "enter") {
+				event.event.target.ownerDocument.documentElement[fullscreen._requestFullscreen](Element.ALLOW_KEYBOARD_INPUT);
+			} else if(event.param === "exit") {
 				event.event.target.ownerDocument[fullscreen._exitFullscreen]();
 			} else {
-				event.event.target.ownerDocument.documentElement[fullscreen._requestFullscreen](Element.ALLOW_KEYBOARD_INPUT);
+				if(event.event.target.ownerDocument[fullscreen._fullscreenElement]) {
+					event.event.target.ownerDocument[fullscreen._exitFullscreen]();
+				} else {
+					event.event.target.ownerDocument.documentElement[fullscreen._requestFullscreen](Element.ALLOW_KEYBOARD_INPUT);
+				}				
 			}
 		});
 	}
diff --git a/editions/tw5.com/tiddlers/messages/WidgetMessage_ tm-full-screen.tid b/editions/tw5.com/tiddlers/messages/WidgetMessage_ tm-full-screen.tid
index 7445c04ab..417dd6ed7 100644
--- a/editions/tw5.com/tiddlers/messages/WidgetMessage_ tm-full-screen.tid	
+++ b/editions/tw5.com/tiddlers/messages/WidgetMessage_ tm-full-screen.tid	
@@ -1,10 +1,28 @@
+caption: tm-full-screen
 created: 20140811112400855
-modified: 20140811113627373
+modified: 20180814215126941
 tags: Messages
 title: WidgetMessage: tm-full-screen
 type: text/vnd.tiddlywiki
-caption: tm-full-screen
 
-The fullscreen message toggles the "fullscreen" mode of the browser, if it supports it.
+The fullscreen message is used to enter, exit or toggle the "fullscreen" mode of the browser, if it supports it. It uses the following properties on the `event` object:
+
+|!Name |!Description |
+|param |`enter` to enter full screen mode, `exit` to exit it, otherwise toggle the full screen status |
+
+The fullscreen message is handled by the TiddlyWiki core.
+
+
+<$macrocall $name='wikitext-example-without-html'
+src='<$button message="tm-full-screen">
+Full screen toggle
+</$button>
+
+<$button message="tm-full-screen" param="enter">
+Full screen enter
+</$button>
+
+<$button message="tm-full-screen" param="exit">
+Full screen exit
+</$button>'/>
 
-The fullscreen message is handled by the TiddlyWiki core.
\ No newline at end of file