Fix UI freeze on "mark all as read/unread" for forums, channels and boards

[jolavillette]

works with retroshare-gui pr/3274

Fix UI freeze on "mark all as read/unread" for forums, channels and boards

Problem

Marking a large GXS group read — right-click → Mark all as read (or unread) — froze the UI for a very long time and could appear to hang indefinitely. On an 8000-post forum the hourglass stayed up for over an hour; force-quitting mid-way left thousands of posts still unread.

Root cause

Two independent amplifiers, both triggered per message:

1. GUI side — the model spawned one detached std::thread per changed post (each blocking up to 5s waiting for its token to complete) and emitted one dataChanged() per post. Marking N posts created ~N threads and ~N signals, all driven from the GUI thread.
2. Backend side — RsGenExchange::processMsgMetaChanges() wrote each status change to the GXS database in its own implicit transaction (one fsync per message). On the SQLCipher-encrypted store this meant thousands of serial encrypted commits.

Fix

Backend (libretroshare)

• RsGeneralDataService: new batch updateMessageMetaData(std::vector<MsgLocMetaData>) overload (default loops over the single version). RsDataService overrides it to persist the whole batch in a single transaction, held under one DB mutex so nothing interleaves.
• RsGenExchange::processMsgMetaChanges(): resolve all status masks first, then persist every queued change through that single transaction. This benefits every GXS service.
• New bulk read-status APIs that queue all changes at once and emit a single event:
  • RsGxsForums::markRead(forumId, msgIds, read)
  • RsGxsChannels::setMessageReadStatus(channelId, msgIds, read)
  • RsPosted::setPostReadStatus(boardId, msgIds, read)

GUI (retroshare-gui)

• GxsForumModel, GxsChannelPostsModel and PostedPostsModel: "mark all as read/unread" now collects the affected message ids, updates the in-memory model, issues one background batch call, and refreshes the view once — instead of one detached thread + one event + one dataChanged() per post.

Result

The GUI thread now does O(n) in-memory work plus one thread and one signal, regardless of how many posts are affected, so it stays responsive on arbitrarily large groups. Persistence happens in a single transaction (one fsync). Works symmetrically for read and unread, on forums, channels and boards.

Notes

• Backwards compatible: the existing single-message markRead / setMessageReadStatus / setPostReadStatus are unchanged; the batch variants are additive.
• This PR pairs with the companion in the other repository (retroshare-gui ⇄ libretroshare): the GUI batch calls require the new backend overloads. Companion PR:

Testing

Open a forum/channel/board with thousands of posts, then right-click → Mark all as read, and again → Mark all as unread:

• the UI stays responsive throughout (no hourglass hang);
• unread counts update immediately;
• the state persists across a restart.