widgets/thread: option for smarter subject in message summary

In the smart mode, display subject only if it's different from parent
(modulo leading re:'s). Since the subject should not change most of the
time, this reduces visual clutter.

2 files changed, 46 insertions, 7 deletions

diff --git a/alot/defaults/alot.rc.spec b/alot/defaults/alot.rc.spec
index d2b7866c..00e527b5 100644
--- a/alot/defaults/alot.rc.spec
+++ b/alot/defaults/alot.rc.spec
@@ -74,6 +74,16 @@ thread_authors_me = string(default='Me')
 #   the thread subject
 thread_subject = option('oldest', 'notmuch', default='notmuch')
 
+# Whether/how to display the subject in the message summary line in thread
+# view. Valid values are:
+#
+# * 'yes'   always display the subject
+# * 'no'    never display the subject
+# * 'smart' use heuristics to decide whether the subject should be shown.
+#           Currently that means the subject is displayed if it is different
+#           from parent message's, or if the message in question has no parent.
+thread_message_summary_subject = option('yes', 'no', 'smart', default = 'smart')
+
 # When constructing the unique list of thread authors, order by date of
 # author's first or latest message in thread
 thread_authors_order_by = option('first_message', 'latest_message', default='first_message')
diff --git a/alot/widgets/thread.py b/alot/widgets/thread.py
index b0276eb0..cc7fbbf2 100644
--- a/alot/widgets/thread.py
+++ b/alot/widgets/thread.py
@@ -29,15 +29,13 @@ class MessageSummaryWidget(urwid.WidgetWrap):
         :param message: a message
         :type message: alot.db.Message
         """
+        author, address = message.get_author()
+        text            = author if author else address
 
-        try:
-            subj = message.headers['Subject']
-        except KeyError:
-            subj = ''
-        subj = re.sub(r'\n\s+', r' ', ','.join(subj))
+        subj = self._extract_subj(message)
+        if subj:
+            text += ': ' + subj
 
-        author, address = message.get_author()
-        text  = '%s: %s' % (author if author != '' else address, subj)
         date = message.get_datestring()
         if date is not None:
             text += " (%s)" % date
@@ -60,6 +58,37 @@ class MessageSummaryWidget(urwid.WidgetWrap):
                              attr, attr_focus)
         super().__init__(line)
 
+    def _extract_subj(self, msg):
+        subj_style = settings.get('thread_message_summary_subject')
+
+        if subj_style == 'no':
+            return ''
+
+        try:
+            subj = ','.join(msg.headers['Subject'])
+        except KeyError:
+            return ''
+
+        # for "smart" display style, check if normalized subject
+        # is the same as parent's
+        if subj_style == 'smart' and msg.parent is not None:
+            try:
+                parent_subj = ','.join(msg.parent.headers['Subject'])
+            except KeyError:
+                pass
+            else:
+                def normalize_subj(subj):
+                    # normalize subject for comparison - replace all
+                    # whitespace sequences with a single space and strip
+                    # leading re:'s
+                    subj = re.sub(r'\s+', ' ', subj)
+                    return re.sub(r'(re:? *)*', '', subj, flags = re.IGNORECASE)
+
+                if normalize_subj(subj) == normalize_subj(parent_subj):
+                    return ''
+
+        return re.sub(r'\n\s+', r' ', subj)
+
 class _MIMEPartWidget(urwid.WidgetWrap):
 
     # when not None, a list of child _MIMEPartWidget subclasses