GUACAMOLE-377: Enforce lower bound on duration of guac_display frames.

src/libguac/display-priv.h

@@ -38,6 +38,13 @@
  */
 #define GUAC_DISPLAY_MAX_LAG_COMPENSATION 500
 
+/**
+ * The minimum amount of time that must elapse between subsequent frames, in
+ * millisconds. After a frame is written, any further frames will be combined
+ * and deferred until after this amount of time has elapsed.
+ */
+#define GUAC_DISPLAY_MIN_FRAME_DURATION 16
+
 /*
  * IMPORTANT: All functions defined within the internals of guac_display that
  * DO NOT acquire locks on their own are given prefixes based on whether they

src/libguac/display-worker.c

@@ -508,6 +508,14 @@ void* guac_display_worker_thread(void* data) {
                     if (required_wait > GUAC_DISPLAY_MAX_LAG_COMPENSATION)
                         required_wait = GUAC_DISPLAY_MAX_LAG_COMPENSATION;
 
+                    /* Apply a reasonable lower bound on the amount of time
+                     * between subsequent frames (reduces server-side
+                     * processing load in the event that the caller starts
+                     * trying to flush a ton of small frames) */
+                    int frame_remaining = GUAC_DISPLAY_MIN_FRAME_DURATION - latency;
+                    if (frame_remaining >= required_wait)
+                        required_wait = frame_remaining;
+
                     /* Allow connected clients to catch up if they're taking
                      * longer to process frames than the server is taking to
                      * generate them */