From a6b155565067d1a97b0164a1132be88b9eaf6d95 Mon Sep 17 00:00:00 2001
From: Johannes Marbach <n0-0ne+github@mailbox.org>
Date: Fri, 23 Feb 2024 21:28:31 +0100
Subject: [PATCH] Clarify the case of HTML-only topics and transition logic
 (#4112)

* Clarify and simplify transition logic

* Clarify the case of HTML-only topics
---
 proposals/3765-rich-room-topics.md | 51 +++++-------------------------
 1 file changed, 8 insertions(+), 43 deletions(-)

diff --git a/proposals/3765-rich-room-topics.md b/proposals/3765-rich-room-topics.md
index 5b423361..fa322c72 100644
--- a/proposals/3765-rich-room-topics.md
+++ b/proposals/3765-rich-room-topics.md
@@ -59,52 +59,17 @@ responses of `/_matrix/client/v3/publicRooms` and
 `/_matrix/client/v1/rooms/{roomId}/hierarchy`. The topic can be kept
 plain text here because this data should commonly only be displayed to
 users that are *not* a member of the room yet. These users will not have
-the same need for rich room topics as users who are inside the room.
+the same need for rich room topics as users who are inside the room. If
+no plain text topic exists, home servers should return an empty topic
+string from these end points. Since this will inevitably lead to bad UX,
+client implementations are encouraged to always include a plain text
+variant when sending `m.topic` events.
 
 ## Transition
 
-The same transition mechanism as in [MSC1767] is proposed. In
-particular, this means a new room version N is introduced. Starting from
-N clients are not permitted to send `m.room.topic` events anymore and
-MUST treat `m.room.topic` as an invalid event type. Instead the new
-`m.topic` event type is to be used.
-
-Similarly, servers use the `m.topic` event type instead of
-`m.room.topic` when creating rooms with a room version greater or equal
-to N.
-
-Specific care should be taken when rooms are upgraded via
-[`/rooms/{roomId}/upgrade`]. If the new room version is greater or
-equal to N, an existing `m.room.topic` event in the old room
-
-``` json5
-{
-  "type": "m.room.topic",
-  "state_key": "",
-  "content": {
-    "topic": "All about pizza"
-  },
-  ...
-}
-```
-
-should be migrated to an `m.topic` event with a single plain-text entry
-in `m.text` in the new room
-
-``` json5
-{
-  "type": "m.topic",
-  "state_key": "",
-  "content": {
-    "m.topic": {
-      "m.text": [{
-          "body": "All about pizza"
-      }]
-    }
-  },
-  ...
-}
-```
+As this MSC replaces `m.room.topic` for an extensible alternative,
+clients and servers are expected to treat `m.room.topic` as invalid in
+extensible event-supporting room versions.
 
 ## Potential issues