add option to delete board if the last user left

README.md

@@ -1,4 +1,4 @@
-# WBO
+ # WBO
 
 WBO is an online collaborative whiteboard that allows many users to draw simultaneously on a large virtual board.
 The board is updated in real time for all connected users, and its state is always persisted. It can be used for many different purposes, including art, entertainment, design, teaching.
@@ -92,6 +92,7 @@ You can see a list of these variables in [`configuration.js`](./server/configura
 Some important environment variables are :
  - `WBO_HISTORY_DIR` : configures the directory where the boards are saved. Defaults to `./server-data/`.
  - `WBO_MAX_EMIT_COUNT` : the maximum number of messages that a client can send per unit of time. Increase this value if you want smoother drawings, at the expense of being susceptible to denial of service attacks if your server does not have enough processing power. By default, the units of this quantity are messages per 4 seconds, and the default value is `192`.
+ - `DELETE_ON_LEAVE` : (default: `false` / `true`) whether the board gets deleted if the last user leaves or not
  - `AUTH_SECRET_KEY` : If you would like to authenticate your boards using jwt, this declares the secret key.
 
 ## Troubleshooting

client-data/js/board.js

@@ -48,8 +48,16 @@ Tools.drawingEvent = true;
 Tools.showMarker = true;
 Tools.showOtherCursors = true;
 Tools.showMyCursor = true;
+Tools.metadata = {users: 1};
 
 Tools.isIE = /MSIE|Trident/.test(window.navigator.userAgent);
+Tools.isInIFrame = function inIframe () {
+    try {
+        return window.self !== window.top;
+    } catch (e) {
+        return true;
+    }
+}()
 
 Tools.socket = null;
 Tools.connect = function () {
@@ -85,6 +93,15 @@ Tools.connect = function () {
 		});
 	});
 
+    //Receive metadata about the board from server
+	this.socket.on("metadata", function (msg) {
+        if (!msg.users) {
+            Tools.metadata.users = 1;
+            console.error("Received a badly formatted message (no users). ", msg);
+        }
+        Tools.metadata.users = msg.users;
+	});
+
 	this.socket.on("reconnect", function onReconnection() {
 		Tools.socket.emit('joinboard', Tools.boardName);
 	});
@@ -342,6 +359,10 @@ Tools.send = function (data, toolName) {
 		"board": Tools.boardName,
 		"data": d
 	};
+    if(d.tool !== "Cursor"){
+        // Reset the downloaded property as the Whiteboard was updated
+        Tools.metadata.downloaded = false;
+    }
 	Tools.socket.emit('broadcast', message);
 };
 
@@ -469,6 +490,10 @@ function resizeCanvas(m) {
 }
 
 function updateUnreadCount(m) {
+    if(m.tool !== "Cursor"){
+        // Reset the downloaded property as the Whiteboard was updated
+        Tools.metadata.downloaded = false;
+    }
 	if (document.hidden && ["child", "update"].indexOf(m.type) === -1) {
 		Tools.newUnreadMessage();
 	}
@@ -711,4 +736,15 @@ Tools.svg.height.baseVal.value = document.body.clientHeight;
 	document.removeEventListener("mouseup", menu_mouseup);
     }
     menu.addEventListener("mousedown", menu_mousedown);
+    // Ask to save before leave 
+    if(Tools.server_config.DELETE_ON_LEAVE && !Tools.isInIFrame){
+        window.addEventListener('beforeunload', function (e) {
+            if (Tools.metadata.users === 1 && Tools.metadata.downloaded === false ) {
+                e.preventDefault(); // If you prevent default behavior in Mozilla Firefox prompt will always be shown
+                e.returnValue = 'The board will be deleted after you leave, make sure you saved the content!';
+            } else {
+                delete e['returnValue'];
+            }
+        });
+    }
 })()

client-data/tools/download/download.js

@@ -53,7 +53,8 @@
         downloadContent(blob, Tools.boardName + ".svg");
     }
 
-    function downloadContent(blob, filename) {
+    function downloadContent(blob, filename){
+        Tools.metadata.downloaded = true;
         if (window.navigator.msSaveBlob) { // Internet Explorer
             window.navigator.msSaveBlob(blob, filename);
         } else {
@@ -67,6 +68,7 @@
             document.body.removeChild(element);
             window.URL.revokeObjectURL(url);
         }
+        Tools.metadata.downloaded = true;
     }
 
     Tools.add({ //The new tool