GUACAMOLE-622: Require guac_terminal_start() to be invoked before the terminal will render frames or accept user input.

src/terminal/terminal.c

@@ -596,6 +596,7 @@ guac_terminal* guac_terminal_create(guac_client* client,
         available_width = 0;
 
     guac_terminal* term = malloc(sizeof(guac_terminal));
+    term->started = false;
     term->client = client;
     term->upload_path_handler = NULL;
     term->file_download_handler = NULL;
@@ -723,6 +724,11 @@ guac_terminal* guac_terminal_create(guac_client* client,
 
 }
 
+void guac_terminal_start(guac_terminal* term) {
+    term->started = true;
+    guac_terminal_notify(term);
+}
+
 void guac_terminal_stop(guac_terminal* term) {
 
     /* Close input pipe and set fds to invalid */
@@ -851,11 +857,13 @@ wait_complete:
 
 int guac_terminal_render_frame(guac_terminal* terminal) {
 
+    guac_client* client = terminal->client;
+
     int wait_result;
 
     /* Wait for data to be available */
     wait_result = guac_terminal_wait(terminal, 1000);
-    if (wait_result) {
+    if (wait_result || !terminal->started) {
 
         guac_timestamp frame_start = guac_timestamp_current();
 
@@ -867,13 +875,14 @@ int guac_terminal_render_frame(guac_terminal* terminal) {
                                 - frame_end;
 
             /* Wait again if frame remaining */
-            if (frame_remaining > 0)
+            if (frame_remaining > 0 || !terminal->started)
                 wait_result = guac_terminal_wait(terminal,
                         GUAC_TERMINAL_FRAME_TIMEOUT);
             else
                 break;
 
-        } while (wait_result > 0);
+        } while (client->state == GUAC_CLIENT_RUNNING
+                && (wait_result > 0 || !terminal->started));
 
         /* Flush terminal */
         guac_terminal_lock(terminal);
@@ -1672,6 +1681,13 @@ int guac_terminal_send_string(guac_terminal* term, const char* data) {
 
 static int __guac_terminal_send_key(guac_terminal* term, int keysym, int pressed) {
 
+    /* Ignore user input if terminal is not started */
+    if (!term->started) {
+        guac_client_log(term->client, GUAC_LOG_DEBUG, "Ignoring user input "
+                "while terminal has not yet started.");
+        return 0;
+    }
+
     /* Hide mouse cursor if not already hidden */
     if (term->current_cursor != GUAC_TERMINAL_CURSOR_BLANK) {
         term->current_cursor = GUAC_TERMINAL_CURSOR_BLANK;
@@ -1845,6 +1861,13 @@ int guac_terminal_send_key(guac_terminal* term, int keysym, int pressed) {
 static int __guac_terminal_send_mouse(guac_terminal* term, guac_user* user,
         int x, int y, int mask) {
 
+    /* Ignore user input if terminal is not started */
+    if (!term->started) {
+        guac_client_log(term->client, GUAC_LOG_DEBUG, "Ignoring user input "
+                "while terminal has not yet started.");
+        return 0;
+    }
+
     /* Determine which buttons were just released and pressed */
     int released_mask =  term->mouse_mask & ~mask;
     int pressed_mask  = ~term->mouse_mask &  mask;

src/terminal/terminal/terminal.h

@@ -171,6 +171,16 @@ struct guac_terminal {
      */
     guac_client* client;
 
+    /**
+     * Whether user input should be handled and this terminal should render
+     * frames. Initially, this will be false, user input will be ignored, and
+     * rendering of frames will be withheld until guac_terminal_start() has
+     * been invoked. The data within frames will still be rendered, and text
+     * data received will still be handled, however actual frame boundaries
+     * will not be sent.
+     */
+    bool started;
+
     /**
      * The terminal render thread.
      */
@@ -526,7 +536,13 @@ struct guac_terminal {
 
 /**
  * Creates a new guac_terminal, having the given width and height, and
- * rendering to the given client.
+ * rendering to the given client. As failover mechanisms and the Guacamole
+ * client implementation typically use the receipt of a "sync" message to
+ * denote successful connection, rendering of frames (sending of "sync") will
+ * be withheld until guac_terminal_start() is called, and user input will be
+ * ignored. The guac_terminal_start() function should be invoked only after
+ * either the underlying connection has truly succeeded, or until visible
+ * terminal output or user input is required.
  *
  * @param client
  *     The client to which the terminal will be rendered.
@@ -604,6 +620,17 @@ int guac_terminal_render_frame(guac_terminal* terminal);
  */
 int guac_terminal_read_stdin(guac_terminal* terminal, char* c, int size);
 
+/**
+ * Notifies the terminal that rendering should begin and that user input should
+ * now be accepted. This function must be invoked following terminal creation
+ * for the end of frames to be signalled with "sync" messages. Until this
+ * function is invoked, "sync" messages will be withheld.
+ *
+ * @param term
+ *     The terminal to start.
+ */
+void guac_terminal_start(guac_terminal* term);
+
 /**
  * Manually stop the terminal to forcibly unblock any pending reads/writes,
  * e.g. forcing guac_terminal_read_stdin() to return and cease all terminal I/O.