Improve message layout

core/views/compose.py

@@ -730,6 +730,8 @@ def _serialize_messages_with_artifacts(
     for item in serialized:
         item["gap_fragments"] = []
         item["metric_fragments"] = []
+        item["block_gap_ms"] = None
+        item["block_gap_display"] = ""
 
     counterpart_identifiers = set(counterpart_identifiers or [])
     snapshot = (
@@ -749,6 +751,17 @@ def _serialize_messages_with_artifacts(
         current_outgoing = _message_is_outgoing_for_analysis(
             msg, counterpart_identifiers
         )
+        if (
+            prev_msg is not None
+            and prev_ts is not None
+            and prev_outgoing is not None
+            and current_outgoing == prev_outgoing
+            and current_ts >= prev_ts
+        ):
+            block_gap_ms = current_ts - prev_ts
+            serialized[idx]["block_gap_ms"] = int(block_gap_ms)
+            serialized[idx]["block_gap_display"] = _format_gap_duration(block_gap_ms)
+
         if (
             prev_msg is not None
             and prev_ts is not None