added sequences with same endpoints

gallery/example1.typ

@@ -65,4 +65,10 @@ Alice <-- Bob: Another authentication Response
   _gap(size: 45)
   _seq("Alice", "Bob", comment: "message 3")
   _seq("Bob", "Alice", comment: "ok", dashed: true)
+})
+
+#chronos.diagram({
+  import "/src/diagram.typ": *
+  _seq("Alice", "Alice", comment: "On the\nright")
+  _seq("Alice", "Alice", flip: true, comment: "On the\nleft")
 })

src/diagram.typ

@@ -7,7 +7,8 @@
   comment: none,
   dashed: false,
   tip: "default",
-  color: black
+  color: black,
+  flip: false
 ) = {
   return ((
     type: "seq",
@@ -17,6 +18,7 @@
     dashed: dashed,
     tip: tip,
     color: color,
+    flip: flip
   ),)
 }
 

src/renderer.typ

@@ -133,26 +133,51 @@
         )
       )
 
-      if elmt.comment != none {
-        let x = calc.min(x1, x2)
-        if x2 < x1 {
-          x += COMMENT-PAD
+      if elmt.p1 == elmt.p2 {
+        x2 = if elmt.flip {x1 - 20} else {x1 + 20}
+
+        if elmt.comment != none {
+          y -= measure(box(elmt.comment)).height / 1pt + 6
+          draw.content(
+            (x1, y),
+            elmt.comment,
+            anchor: if elmt.flip {"south-east"} else {"south-west"},
+            padding: 3pt
+          )
         }
-        y -= measure(box(elmt.comment)).height / 1pt + 6
-        draw.content(
-          (x, y),
-          elmt.comment,
-          anchor: "south-west",
-          padding: 3pt
+
+        draw.line(
+          (x1, y),
+          (x2, y),
+          (x2, y - 10),
+          (x1, y - 10),
+          ..style
+        )
+        y -= 10
+
+      } else {
+        if elmt.comment != none {
+          let x = calc.min(x1, x2)
+          if x2 < x1 {
+            x += COMMENT-PAD
+          }
+          y -= measure(box(elmt.comment)).height / 1pt + 6
+          draw.content(
+            (x, y),
+            elmt.comment,
+            anchor: "south-west",
+            padding: 3pt
+          )
+        }
+
+        draw.line(
+          (x1, y),
+          (x2, y),
+          ..style
         )
       }
-
-      draw.line(
-        (x1, y),
-        (x2, y),
-        ..style
-      )
       y -= Y-SPACE
+
     } else if elmt.type == "grp" {
       let m = measure(
         box(