From cc574bfd03c7be6aea17a00fb0f46a81113c38a5 Mon Sep 17 00:00:00 2001
From: matt335672 <30179339+matt335672@users.noreply.github.com>
Date: Mon, 9 Sep 2024 15:07:31 +0100
Subject: [PATCH] Regression: Support fixed-size VNC sessions

This is a regression introduced in v0.10.x

This version introduced a state machine to handle resizes requested
by the client and the server. Most configurations support resizeable
sessions, but one that doesn't is xrdp connecting to x11vnc on (e.g.) a
Raspberry PI.

If the session size requested by a client is differnt from the x11vnc
size, an error is logged and the state machine fails to complete,
resulting in a black screen.

This PR handles the problem by queueing a resize to the supported
server size and then continuing with the state machine. It's not an
optimal solution, but involves the least change to v0.10.x code.

(cherry picked from commit 984b71449ebc6c09e909b7078d36769e46f87ca0)
---
 vnc/vnc.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/vnc/vnc.c b/vnc/vnc.c
index ce53fbfc..3b1181dc 100644
--- a/vnc/vnc.c
+++ b/vnc/vnc.c
@@ -1201,10 +1201,6 @@ lib_framebuffer_waiting_for_resize_confirm(struct vnc *v)
                 LOG(LOG_LEVEL_DEBUG, "VNC server successfully resized");
                 log_screen_layout(LOG_LEVEL_INFO, "NewLayout", &layout);
                 v->server_layout = layout;
-                // If this resize was requested by the client mid-session
-                // (dynamic resize), we need to tell xrdp_mm that
-                // it's OK to continue with the resize state machine.
-                error = v->server_monitor_resize_done(v);
             }
             else
             {
@@ -1212,10 +1208,23 @@ lib_framebuffer_waiting_for_resize_confirm(struct vnc *v)
                     "VNC server resize failed - error code %d [%s]",
                     response_code,
                     rfb_get_eds_status_msg(response_code));
-                /* Force client to same size as server */
+                // This is awkward. The client has asked for a specific size
+                // which we can't support.
+                //
+                // Currently we handle this by queueing a resize to our
+                // supported size, and continuing with the resize state
+                // machine in xrdp_mm.c
                 LOG(LOG_LEVEL_WARNING, "Resizing client to server");
                 error = resize_client_to_server(v, 0);
             }
+
+            if (error == 0)
+            {
+                // If this resize was requested by the client mid-session
+                // (dynamic resize), we need to tell xrdp_mm that
+                // it's OK to continue with the resize state machine.
+                error = v->server_monitor_resize_done(v);
+            }
             v->resize_status = VRS_DONE;
         }
     }