fix(www): ensure state-changing GETs are never browser-cached

mtda-www

@@ -99,6 +99,14 @@ class RemoteCallHandler(BaseHandler):
     Handles common logic for offloading blocking calls to a thread pool
     and centralized error handling for remote interactions.
     """
+    def set_default_headers(self):
+        # These GETs change state (keyboard-input, mouse-move, ...). The
+        # browser must not cache them, or a repeated request (e.g. the
+        # same key typed twice) would never reach the server.
+        self.set_header("Cache-Control",
+                        "no-store, no-cache, must-revalidate, max-age=0")
+        self.set_header("Pragma", "no-cache")
+
     async def get(self):
         try:
             logger.debug(f"Request: {self.__class__.__name__}")

mtda/templates/index.html

@@ -504,6 +504,10 @@
     <script src="./assets/keyboard.js"></script>
     <script src="./assets/keysight.js"></script>
     <script type=text/javascript>
+      // These GETs change state (keyboard-input, mouse-move, ...). Stop
+      // the browser from caching them, or a repeated request would be
+      // dropped instead of reaching the server.
+      $.ajaxSetup({ cache: false });
       window.addEventListener("keydown", function(event) {
         // check if the video window is active or ignore keydown event
         if (!videoWindow || !videoWindow.focused) {