more efficient data representation

avoid storing duplicated information for every point in a line

client-data/js/board.js

@@ -434,10 +434,20 @@ function handleMessage(message) {
     console.error("Received a badly formatted message (no tool). ", message);
   }
   if (message.tool) messageForTool(message);
-  if (message._children) return batchCall(handleMessage, message._children);
+  if (message._children) return batchCall(childMessageHandler(message), message._children);
   else return Promise.resolve();
 }
 
+// Takes a parent message, and returns a function that will handle a single child message
+function childMessageHandler(parent) {
+  return function handleChild(child) {
+    if (!child.parent) child.parent = parent.id;
+    if (!child.type) child.type = "child";
+    if (!child.tool) child.tool = parent.tool;
+    return handleMessage(child);
+  };
+}
+
 Tools.unreadMessagesCount = 0;
 Tools.newUnreadMessage = function () {
   Tools.unreadMessagesCount++;

server/boardData.js

@@ -171,7 +171,12 @@ class BoardData {
         if (id) this.copy(id, message);
         break;
       case "child":
-        this.addChild(message.parent, message);
+        // We don't need to store 'type', 'parent', and 'tool' for each child. They will be rehydrated from the parent on the client side
+        const parent = message.parent;
+        delete message.type;
+        delete message.parent;
+        delete message.tool;
+        this.addChild(parent, message);
         break;
       case "clear":
         if (jwtauth.roleInBoard(message.token, message.board) === "moderator") {