Basic, dumb saving in TiddlyFox now works

It seems to work OK, but could do with more of a user interface for
confirmations and so on...

tiddlyfox/extension/content/inject.js

@@ -0,0 +1,45 @@
+/*
+The JavaScript in this file is injected into each TiddlyWiki page that loads
+*/
+
+(function () {
+
+	/*
+	Returns true if successful, false if failed, null if not available
+	*/
+	var injectedSaveFile = function(path,content) {
+		// Find the message box element
+		var messageBox = document.getElementById("tiddlyfox-message-box");
+		if(messageBox) {
+			// Create the message element and put it in the message box
+			var message = document.createElement("div");
+			message.setAttribute("tiddlyfox-path",path);
+			message.setAttribute("tiddlyfox-content",content);
+			messageBox.appendChild(message);
+			// Create and dispatch the custom event to the extension
+			var event = document.createEvent("Events");
+			event.initEvent("tiddlyfox-save-file",true,false);
+			message.dispatchEvent(event);
+		}
+		return true;
+	};
+
+	/*
+	Returns text if successful, false if failed, null if not available
+	*/
+	var injectedLoadFile = function(path) {
+		try {
+			// Just the read the file synchronously
+			var xhReq = new XMLHttpRequest();
+			xhReq.open("GET", "file://" + path, false);
+			xhReq.send(null);
+			return xhReq.responseText;
+		} catch(ex) {
+			return false;
+		}
+	};
+
+	window.mozillaSaveFile = injectedSaveFile;
+	window.mozillaLoadFile = injectedLoadFile;
+
+})();

tiddlyfox/extension/content/overlay.js

@@ -1,12 +1,96 @@
-var TiddlyFox = {
-  onLoad: function() {
-    // initialization code
-    this.initialized = true;
-  },
+/*
+
+The JavaScript code in this file is executed via `overlay.xul` when Firefox starts up.
+
+*/
+
+var TiddlyFox = {
+
+	// Called when the main browser has loaded
+	onLoad: function(event) {
+		// Register a page load event
+		var appcontent = document.getElementById("appcontent");
+		if(appcontent){
+			appcontent.addEventListener("DOMContentLoaded",TiddlyFox.onPageLoad,true);
+		}
+	},
+
+	// Called each time a page loads
+	onPageLoad: function(event) {
+		// Get the document and window
+		var doc = event.originalTarget,
+			win = doc.defaultView;
+		// If it is a TiddlyWiki
+		if(TiddlyFox.isTiddlyWiki(doc,win)) {
+			alert("TiddlyFox: Enabling TiddlyWiki file saving");
+			TiddlyFox.injectPage(doc);
+		}
+	},
+
+	injectPage: function(doc) {
+		// Inject the message box
+		var messageBox = doc.createElement("div");
+		messageBox.id = "tiddlyfox-message-box";
+		messageBox.style.display = "none";
+		doc.body.appendChild(messageBox);
+		// Attach the event handler to the message box
+		messageBox.addEventListener("tiddlyfox-save-file",TiddlyFox.onSaveFile,false);
+		// Load the script text
+		var xhReq = new XMLHttpRequest();
+		xhReq.open("GET","chrome://tiddlyfox/content/inject.js",false);
+		xhReq.send(null);
+		var injectCode = xhReq.responseText;
+		// Inject the script
+		var code = doc.createTextNode(injectCode);
+		var scr = doc.createElement("script");
+		scr.type = "text/javascript";
+		scr.appendChild(code);
+		doc.getElementsByTagName("head")[0].appendChild(scr)
+	},
+
+	saveFile: function(filePath,content) {
+		try {
+			netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
+			var file = Components.classes["@mozilla.org/file/local;1"].createInstance(Components.interfaces.nsILocalFile);
+			file.initWithPath(filePath);
+			if(!file.exists())
+				file.create(0,0x01B4);// 0x01B4 = 0664
+			var out = Components.classes["@mozilla.org/network/file-output-stream;1"].createInstance(Components.interfaces.nsIFileOutputStream);
+			out.init(file,0x22,0x04,null);
+			out.write(content,content.length);
+			out.flush();
+			out.close();
+			return true;
+		} catch(ex) {
+			return false;
+		}
+	},
+
+	onSaveFile: function(event) {
+		// Get the details from the message
+		var message = event.target,
+			path = message.getAttribute("tiddlyfox-path"),
+			content = message.getAttribute("tiddlyfox-content");
+		// Save the file
+		TiddlyFox.saveFile(path,content);
+		// Remove the message element from the message box
+		message.parentNode.removeChild(message);
+		return false;
+	},
+
+	// Called via `overlay.xul` when the menu item is selected
+	onMenuItemCommand: function() {
+		window.open("chrome://tiddlyfox/content/hello.xul", "", "chrome");
+	},
+
+	isTiddlyWiki: function(doc,win) {
+		// Test whether the document is a TiddlyWiki (we don't have access to JS objects in it)
+		return (doc.scripts[0].id === "versionArea");
+	}
 
-  onMenuItemCommand: function() {
-    window.open("chrome://tiddlyfox/content/hello.xul", "", "chrome");
-  }
 };
 
-window.addEventListener("load", function(e) { TiddlyFox.onLoad(e); }, false); 
+window.addEventListener("load",function load(event) {
+	window.removeEventListener("load",load,false);
+	TiddlyFox.onLoad(event);
+},false);