thread: implement tree decorations

They were temporarily removed in the previous commit.
Still not working:
- theming for the decorations
- drawing the connector line properly for expanded messages
- configurable indentation

1 files changed, 53 insertions, 0 deletions

diff --git a/alot/widgets/thread.py b/alot/widgets/thread.py
index 0b4e2404..ebbc4704 100644
--- a/alot/widgets/thread.py
+++ b/alot/widgets/thread.py
@@ -290,3 +290,56 @@ class MessageWidget(urwid.WidgetWrap):
         matches given `querystring`
         """
         self.display_content = not self._message.matches(querystring)
+
+class ThreadNode(urwid.WidgetWrap):
+    _ARROW  = '➤'
+    _HBAR   = '─'
+    _VBAR   = '│'
+    _TNODE  = '├'
+    _CORNER = '└'
+
+    _decor_text        = None
+    _have_next_sibling = None
+
+    def __init__(self, msg_wgt, thread, pos, indent):
+        msg = msg_wgt.get_message()
+
+        if msg.depth == 0:
+            wgt = msg_wgt
+        else:
+            self._decor_text = urwid.Text('')
+            wgt = urwid.Columns([('pack', self._decor_text), msg_wgt])
+
+            ancestor_chain = [msg]
+            for p in msg.parents():
+                ancestor_chain.insert(0, p)
+
+            have_sibling = []
+            for d, m in enumerate(ancestor_chain):
+                if d == 0:
+                    have_sibling.append(m != thread.toplevel_messages[-1])
+                else:
+                    have_sibling.append(m != ancestor_chain[d - 1].replies[-1])
+
+            self._have_next_sibling = have_sibling
+
+        super().__init__(wgt)
+
+        self.set_indent(indent)
+
+    def set_indent(self, indent):
+        if self._decor_text is None:
+            return
+
+        seg_text = []
+        if indent > 0:
+            depth = len(self._have_next_sibling) - 1
+            for d in range(depth):
+                if d == depth - 1:
+                    corner = self._TNODE if self._have_next_sibling[d + 1] else self._CORNER
+                    seg_text.append(corner + self._ARROW)
+                else:
+                    bar = self._VBAR if self._have_next_sibling[d + 1] else ' '
+                    seg_text.append(bar + ' ')
+
+        self._decor_text.set_text(''.join(seg_text))