From f5a0be0a7b27279544e15770578f2bf830e343d2 Mon Sep 17 00:00:00 2001
From: Slavi Pantaleev <slavi@devture.com>
Date: Wed, 12 Mar 2025 09:09:21 +0200
Subject: [PATCH] Add support for configuring Synapse's MSC4140 (Delayed
 Events) experimental feature

This is required by Element Call.

Ref:

- https://github.com/element-hq/element-call/blob/93ae2aed9841e0b066d515c56bd4c122d2b591b2/docs/self-hosting.md#a-matrix-homeserver
- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3562
---
 roles/custom/matrix-synapse/defaults/main.yml      | 14 ++++++++++++++
 .../templates/synapse/homeserver.yaml.j2           |  7 +++++++
 2 files changed, 21 insertions(+)

diff --git a/roles/custom/matrix-synapse/defaults/main.yml b/roles/custom/matrix-synapse/defaults/main.yml
index 9a99d5cd1..113edb498 100644
--- a/roles/custom/matrix-synapse/defaults/main.yml
+++ b/roles/custom/matrix-synapse/defaults/main.yml
@@ -1261,6 +1261,20 @@ matrix_synapse_experimental_features_msc4108_enabled: false
 # Set this to false if you still want to disable to API for some reason. Note that doing so breaks Element X compatibility though.
 matrix_synapse_experimental_features_msc3266_enabled: true
 
+# Controls whether to enable the "Delayed Events" experimental feature.
+# Delayed events are required for proper call (Element Call) participation signalling.
+# If disabled it is very likely that you end up with stuck calls in Matrix rooms.
+#
+# Related to `matrix_synapse_max_event_delay_duration`
+#
+# See https://github.com/matrix-org/matrix-spec-proposals/pull/4140
+matrix_synapse_experimental_features_msc4140_enabled: false
+
+# Controls the maximum allowed duration by which sent events can be delayed, as per MSC4140.
+#
+# See `matrix_synapse_experimental_features_msc4140_enabled`.
+matrix_synapse_max_event_delay_duration: 24h
+
 # Enable this to activate the REST auth password provider module.
 # See: https://github.com/ma1uta/matrix-synapse-rest-password-provider
 matrix_synapse_ext_password_provider_rest_auth_enabled: false
diff --git a/roles/custom/matrix-synapse/templates/synapse/homeserver.yaml.j2 b/roles/custom/matrix-synapse/templates/synapse/homeserver.yaml.j2
index 4daff2fef..ebdf323d8 100644
--- a/roles/custom/matrix-synapse/templates/synapse/homeserver.yaml.j2
+++ b/roles/custom/matrix-synapse/templates/synapse/homeserver.yaml.j2
@@ -2987,5 +2987,12 @@ experimental_features:
   {% if matrix_synapse_experimental_features_msc4108_enabled %}
   msc4108_enabled: true
   {% endif %}
+  {% if matrix_synapse_experimental_features_msc4140_enabled %}
+  msc4140_enabled: true
+  {% endif %}
+
+{% if matrix_synapse_experimental_features_msc4140_enabled %}
+max_event_delay_duration: {{ matrix_synapse_max_event_delay_duration | to_json }}
+{% endif %}
 
 # vim:ft=yaml