From 7185651b8cc9b5f3a1ff61b9316fbfb1941b162d Mon Sep 17 00:00:00 2001
From: Klement Sekera <klement.sekera@gmail.com>
Date: Wed, 11 Mar 2026 08:07:26 +0100
Subject: [PATCH] Add thread_select_unread setting to open threads at oldest
 unread message

When enabled, opening a thread selects the oldest unread matching message
instead of the oldest matching message. Falls back to the most recent message
if all messages are read. Also fixes a crash in get_last_msg_idx when called
with an invalid root index.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 dodo/settings.py |  8 ++++++++
 dodo/thread.py   | 25 ++++++++++++++++++++-----
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/dodo/settings.py b/dodo/settings.py
index c112eb2..44ddb39 100644
--- a/dodo/settings.py
+++ b/dodo/settings.py
@@ -151,6 +151,14 @@
     * 'thread': tree view, following the various subthreads
 """
 
+thread_select_unread = False
+"""When opening a thread, select the oldest unread matching message
+
+If True, the oldest unread matching message is selected when opening a thread.
+If all messages are read, the most recent message is selected instead.
+If False (the default), the oldest matching message is selected.
+"""
+
 gnupg_home = None
 """Directory containg GnuPG keys
 
diff --git a/dodo/thread.py b/dodo/thread.py
index ab9c50a..85f174d 100644
--- a/dodo/thread.py
+++ b/dodo/thread.py
@@ -307,6 +307,10 @@ def _fetch_matching_ids(self) -> set[str]:
         return set(json.loads(r.stdout))
 
     def get_last_msg_idx(self, parent: QModelIndex=QModelIndex()) -> QModelIndex:
+        if not parent.isValid():
+            if self.rowCount() == 0:
+                return QModelIndex()
+            return self.get_last_msg_idx(self.index(self.rowCount()-1, 0))
         children = parent.internalPointer().children
         if children:
             return self.get_last_msg_idx(self.index(len(children)-1, 0, parent))
@@ -421,11 +425,22 @@ def find(self, msg_id: str) -> QModelIndex:
 
     def default_message(self) -> QModelIndex:
         """Return the index of either the oldest matching message or the last message
-        in the thread."""
-        for idx in self.iterate_indices():
-            if self.message_at(idx)['id'] in self.matches:
-                return idx
-        return self.get_last_msg_idx()
+        in the thread.
+
+        If :func:`~dodo.settings.thread_select_unread` is True, prefer the oldest
+        unread matching message, falling back to the last message if all are read.
+        """
+        if settings.thread_select_unread:
+            for idx in self.iterate_indices():
+                msg = self.message_at(idx)
+                if msg['id'] in self.matches and 'unread' in msg['tags']:
+                    return idx
+            return self.get_last_msg_idx()
+        else:
+            for idx in self.iterate_indices():
+                if self.message_at(idx)['id'] in self.matches:
+                    return idx
+            return self.get_last_msg_idx()
 
     def default_collapsed(self) -> set[str]:
         irrelevant_branches = set()