GUACAMOLE-1196: Implement our own function for sending size updates to server.

    The current state of the libvncclient implementation of the SendExtDesktopSize
    function is broken and does not work reliably with VNC servers. In order
    to still support this functionality until an updated libvncclient version
    is release, I went ahead and implemented an internal version of that
    function.

Author: necouchman

src/protocols/vnc/display.c

@@ -157,6 +157,98 @@ void guac_vnc_copyrect(rfbClient* client, int src_x, int src_y, int w, int h, in
 
 #ifdef ENABLE_VNC_DESKTOP_SIZE
 
+/**
+ * This function does the actual work of sending the message to the RFB/VNC
+ * server to request the resize, and then makes sure that the client frame
+ * buffer is updated, as well.
+ *
+ * @param client
+ *     The remote frame buffer client that is triggering the resize
+ *     request.
+ *
+ * @param width
+ *     The updated width of the screen.
+ *
+ * @param height
+ *     The updated height of the screen.
+ *
+ * @return
+ *     TRUE if the screen update was sent to the server, otherwise false. Note
+ *     that a successful send of the resize message to the server does NOT mean
+ *     that the server has any obligation to resize the display - it only
+ *     indicates that the VNC library has successfully sent the request.
+ */
+static rfbBool guac_vnc_send_desktop_size(rfbClient* client, int width, int height) {
+
+    /* Get the Guacamole client data */
+    guac_client* gc = rfbClientGetClientData(client, GUAC_VNC_CLIENT_KEY);
+
+    /* Don't send an update if the sreen appears to be uninitialized. */
+    if (client->screen.width == 0 || client->screen.height == 0) {
+        guac_client_log(gc, GUAC_LOG_ERROR, "Screen has not been initialized, cannot send resize.");
+        return FALSE;
+    }
+    
+    /* Don't send an update if the requested dimensions are identical to current dimensions. */
+    if (client->screen.width == rfbClientSwap16IfLE(width) && client->screen.height == rfbClientSwap16IfLE(height)) {
+        guac_client_log(gc, GUAC_LOG_WARNING, "Screen size has not changed, not sending update.");
+        return FALSE;
+    }
+
+    /**
+     * Note: The RFB protocol requires two message types to be sent during a
+     * resize request - the first for the desktop size (total size of all
+     * monitors), and then a message for each screen that is attached to the 
+     * remote server. Both libvncclient and Guacamole only support a single
+     * screen, so we send the desktop resize and screen resize with (nearly)
+     * identical data, but if one or both of these components is updated in the
+     * future to support multiple screens, this will need to be re-worked.
+     */
+
+    /* Set up the messages. */
+    rfbSetDesktopSizeMsg size_msg;
+    rfbExtDesktopScreen new_screen;
+
+    /* Configure the desktop size update message. */
+    size_msg.type = rfbSetDesktopSize;
+    size_msg.width = rfbClientSwap16IfLE(width);
+    size_msg.height = rfbClientSwap16IfLE(height);
+    size_msg.numberOfScreens = 1;
+
+    /* Configure the screen update message. */
+    new_screen.id = client->screen.id;
+    new_screen.x = client->screen.x;
+    new_screen.y = client->screen.y;
+    new_screen.flags = client->screen.flags;
+    new_screen.width = rfbClientSwap16IfLE(width);
+    new_screen.height = rfbClientSwap16IfLE(height);
+
+    /* Stop updates while the resize is in progress. */
+    client->requestedResize = TRUE;
+
+    /* Send the resize messages to the remote server. */
+    if (!WriteToRFBServer(client, (char *)&size_msg, sz_rfbSetDesktopSizeMsg)
+        || !WriteToRFBServer(client, (char *)&new_screen, sz_rfbExtDesktopScreen)) {
+
+        guac_client_log(gc, GUAC_LOG_ERROR, "Failed to send new desktop and screen size to the VNC server.");
+        return FALSE;
+
+    }
+
+    /* Update the client frame buffer with the requested size. */
+    client->screen.width = rfbClientSwap16IfLE(width);
+    client->screen.height = rfbClientSwap16IfLE(height);
+
+    /* Request a full screen update. */
+    client->requestedResize = FALSE;
+    if (!SendFramebufferUpdateRequest(client, 0, 0, width, height, FALSE)) {
+        guac_client_log(gc, GUAC_LOG_WARNING, "Failed to request a full screen update.");
+    }
+
+    /* Update should be successful. */
+    return TRUE;
+}
+
 void guac_vnc_display_set_size(rfbClient* client, int width, int height) {
 
     /* Get the VNC client */
@@ -171,7 +263,11 @@ void guac_vnc_display_set_size(rfbClient* client, int width, int height) {
 
     /* Send the display size update. */
     pthread_mutex_lock(&(vnc_client->message_lock));
-    SendExtDesktopSize(client, width, height);
+    guac_client_log(gc, GUAC_LOG_TRACE, "Setting VNC display size.");
+    if (guac_vnc_send_desktop_size(client, width, height))
+        guac_client_log(gc, GUAC_LOG_TRACE, "Successfully sent desktop size message.");
+    else
+        guac_client_log(gc, GUAC_LOG_TRACE, "Failed to send desktop size message.");
     pthread_mutex_unlock(&(vnc_client->message_lock));
 
 }

src/protocols/vnc/input.c

@@ -69,6 +69,8 @@ int guac_vnc_user_key_handler(guac_user* user, int keysym, int pressed) {
 
 int guac_vnc_user_size_handler(guac_user* user, int width, int height) {
 
+    guac_user_log(user, GUAC_LOG_TRACE, "Running user size handler.");
+
     /* Get the Guacamole VNC client */
     guac_vnc_client* vnc_client = (guac_vnc_client*) user->client->data;
 
@@ -79,4 +81,4 @@ int guac_vnc_user_size_handler(guac_user* user, int width, int height) {
 
 }
 
-#endif // ENABLE_VNC_DESKTOP_SIZE
+#endif // ENABLE_VNC_DESKTOP_SIZE