GUACAMOLE-462: Allow pending display frames to be cancelled.

guacamole-common-js/src/main/webapp/modules/Display.js

@@ -201,6 +201,22 @@ Guacamole.Display = function() {
      */
     function Frame(callback, tasks) {
 
+        /**
+         * Cancels rendering of this frame and all associated tasks. The
+         * callback provided at construction time, if any, is not invoked.
+         */
+        this.cancel = function cancel() {
+
+            callback = null;
+
+            tasks.forEach(function cancelTask(task) {
+                task.cancel();
+            });
+
+            tasks = [];
+
+        };
+
         /**
          * Returns whether this frame is ready to be rendered. This function
          * returns true if and only if ALL underlying tasks are unblocked.
@@ -271,6 +287,16 @@ Guacamole.Display = function() {
          */
         this.blocked = blocked;
 
+        /**
+         * Cancels this task such that it will not run. The task handler
+         * provided at construction time, if any, is not invoked. Calling
+         * execute() after calling this function has no effect.
+         */
+        this.cancel = function cancel() {
+            task.blocked = false;
+            taskHandler = null;
+        };
+
         /**
          * Unblocks this Task, allowing it to run.
          */
@@ -417,6 +443,27 @@ Guacamole.Display = function() {
 
     };
 
+    /**
+     * Cancels rendering of all pending frames and associated rendering
+     * operations. The callbacks provided to outstanding past calls to flush(),
+     * if any, are not invoked.
+     */
+    this.cancel = function cancel() {
+
+        frames.forEach(function cancelFrame(frame) {
+            frame.cancel();
+        });
+
+        frames = [];
+
+        tasks.forEach(function cancelTask(task) {
+            task.cancel();
+        });
+
+        tasks = [];
+
+    };
+
     /**
      * Sets the hotspot and image of the mouse cursor displayed within the
      * Guacamole display.