GUACAMOLE-288: Add support for multi-monitor connections. #560

corentin-soriano · 2024-10-20T09:43:37Z

Allows as is to add multiple monitors of the same dimensions in RDP protocol if the server supports it.
I haven't looked at the VNC part yet.

Client side PR : apache/guacamole-client#1061

POC:

src/protocols/rdp/channels/disp.c

Pierre-Gronau-ndaal · 2025-04-15T18:56:39Z

it will be great if we bring that to main

necouchman · 2025-04-15T19:34:45Z

it will be great if we bring that to main

Yes, that is the plan, once the code is finalized and has been fully reviewed.

…ates.

…hen adding a new monitor.

Vertganti · 2025-06-26T08:31:50Z

Frequently resizing a monitor window, e.g. by using Maximize and Restore down of the window in quick succession, can cause a RDP disconnect with the following message in the guacd logs:

GUAC_ASSERT in guac_rdp_gdi_desktop_resize() failed at gdi.c:172.

Assertion code

Is it possible to wait for the flush or just discard the affected window instead of crashing the connection?

corentin-soriano · 2025-07-07T07:16:54Z

Frequently resizing a monitor window, e.g. by using Maximize and Restore down of the window in quick succession, can cause a RDP disconnect with the following message in the guacd logs:
GUAC_ASSERT in guac_rdp_gdi_desktop_resize() failed at gdi.c:172.
Assertion code

Is it possible to wait for the flush or just discard the affected window instead of crashing the connection?

Which version of freerdp are you using?
If you are on v3, can you update it to at least version 3.8.0?

Vertganti · 2025-07-07T07:55:08Z

I'm using the Dockerfile from the repository which defaults to FreeRDP 2. The exact version is 2.11.7. I can try using FreeRDP 3 to see if that improves anything.

corentin-soriano · 2025-07-07T08:01:45Z

I'm using the Dockerfile form the repository which defaults to FreeRDP 2. The exact version is 2.11.7. I can try using FreeRDP 3 to see if that improves anything.

This is potentially a bug in FreeRDP. This assertion is mandatory in version 2.
Are you sure you can't reproduce this with a single monitor?

Vertganti · 2025-07-07T11:35:04Z

I'm using the Dockerfile form the repository which defaults to FreeRDP 2. The exact version is 2.11.7. I can try using FreeRDP 3 to see if that improves anything.

This is potentially a bug in FreeRDP. This assertion is mandatory in version 2. Are you sure you can't reproduce this with a single monitor?

I was able to reproduce it with one monitor with the FreeRDP 2 build.

EDIT: It does not reproduce with FreeRDP 3, independent of the number of monitors.

weberr13 · 2025-07-07T18:52:28Z

src/protocols/rdp/channels/disp.c

+        guac_rdp_client* rdp_client = (guac_rdp_client*) client->data;
+
+        pthread_mutex_lock(&(rdp_client->message_lock));
+        disp->disp->SendMonitorLayout(disp->disp, monitors_count, monitors);


I may not understand the API, but naively I feel like when a pointer (monitors) is sent via a signal that memory must either be given to the receiver (eg it is now responsible for freeing monitors) or it would have to signal it is "done" with the memory somehow (which I cannot see happening). I believe from line 422 that there is a possible segmentation violation with the receiver of SendMonitorLayout reading free'ed memory.

weberr13 · 2025-07-07T18:54:32Z

src/protocols/rdp/client.c

+    /* Send current max allowed secondary monitors */
+    guac_client_stream_argv(client, broadcast_socket, "text/plain",
+            "secondary-monitors", max_monitors);
+    guac_mem_free(max_monitors);


same concern as above, who "owns" the char* max_monitors? does guac_client_stream_argv copy from max_monitors?

weberr13 · 2025-07-07T18:58:54Z

src/protocols/rdp/gdi.c

+    /* Make json string containing monitor information */
+    char json[JSON_BUFFER_SIZE];
+    int pos = 0;
+    pos += snprintf(json + pos, JSON_BUFFER_SIZE - pos, "{");


nit: While there may be concerns about grabbing an external dependency, when it comes to "never re-invent the wheel" any manual string manipulation to do json generation/parsing is king. Libraries like

https://github.com/nlohmann/json

will allow "C++ like" json parsing and generation that covers all the corner cases that JSON hides from the average user.

weberr13 · 2025-07-07T19:01:12Z

src/protocols/rdp/gdi.c

+        }
+
+        /* Append monitor information to JSON string */
+        pos += snprintf(json + pos, JSON_BUFFER_SIZE - pos,


A small piece of my soul is severed and sent to the depths of Hades every time I see sprintf generating json.

lirannisani · 2025-09-04T06:23:49Z

@necouchman @corentin-soriano
Thanks for adding this feature!
Do you plan to merge it into the main branch?

corentin-soriano · 2025-09-04T08:47:13Z

@necouchman @corentin-soriano Thanks for adding this feature! Do you plan to merge it into the main branch?

I still have some things to finalize before we can merge.
I haven't had time to continue lately but the subject has not been forgotten!

corentin-soriano marked this pull request as draft October 20, 2024 09:43

corentin-soriano force-pushed the GUACAMOLE-288_multi_monitors branch from 78954b5 to d829739 Compare October 20, 2024 10:05

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corentin-soriano force-pushed the GUACAMOLE-288_multi_monitors branch from 683800f to 62c8b1e Compare January 9, 2025 09:00

corentin-soriano force-pushed the GUACAMOLE-288_multi_monitors branch from 62c8b1e to 4ee5e1b Compare January 21, 2025 09:32

corentin-soriano mentioned this pull request Feb 15, 2025

GUACAMOLE-288: Add support for multi-monitor connections on RDP. apache/guacamole-client#1061

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neandrake reviewed Feb 21, 2025

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corentin-soriano force-pushed the GUACAMOLE-288_multi_monitors branch from 4ee5e1b to ac08c95 Compare February 22, 2025 15:41

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corentin-soriano added 6 commits June 17, 2025 17:49

GUACAMOLE-288: Receive the monitors count in resize channel.

c11e57b

GUACAMOLE-288: Handle multiple monitors in RDP via resize display upd…

164c714

…ates.

GUACAMOLE-288: Add parameter to limit the usage of multiple monitors.

6e86596

GUACAMOLE-288: Allow windows to have different dimensions.

48a7d90

GUACAMOLE-288: Send monitor layout via layer set parameter.

9172fba

GUACAMOLE-288: Send mouse icon after resize to ensure it is visible w…

5294c1b

…hen adding a new monitor.

corentin-soriano force-pushed the GUACAMOLE-288_multi_monitors branch from eda5067 to 5294c1b Compare June 17, 2025 15:49

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weberr13 reviewed Jul 7, 2025

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necouchman mentioned this pull request Sep 24, 2025

Multi screen #616

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GUACAMOLE-288: Add support for multi-monitor connections. #560

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