added separators

gallery/example1.typ

@@ -42,4 +42,15 @@ Alice <-- Bob: Another authentication Response
     })
     _seq("Alice", "Bob", comment: "Log attack end")
   })
+})
+
+#chronos.diagram({
+  import "/src/diagram.typ": *
+  _sep("Initialization")
+  _seq("Alice", "Bob", comment: "Authentication Request")
+  _seq("Bob", "Alice", comment: "Authentication Response", dashed: true)
+  
+  _sep("Repetition")
+  _seq("Alice", "Bob", comment: "Another authentication Request")
+  _seq("Bob", "Alice", comment: "another authentication Response", dashed: true)
 })

src/diagram.typ

@@ -48,11 +48,17 @@
   ),)
 }
 
+#let _sep(name) = {
+  return ((
+    type: "sep",
+    name: name
+  ),)
+}
+
 #let diagram(elements) = {
   let participants = ()
   let elmts = elements
   let i = 0
-  let a = elmts.len()
   while i < elmts.len() {
     let elmt = elmts.at(i)
     if elmt.type == "grp" {
@@ -67,9 +73,6 @@
     }
     i += 1
   }
-  let b = elmts.len()
-  [#a / #b]
-  [#elmts.map(e => e.type)]
 
   for elmt in elmts {
     if elmt.type == "par" {

src/renderer.typ

@@ -169,6 +169,37 @@
       draw-group(x0, x1, start-y, y, group)
 
       y -= Y-SPACE
+
+    } else if elmt.type == "sep" {
+      let x0 = x-pos.first() - 20
+      let x1 = x-pos.last() + 20
+      let m = measure(
+        box(
+          elmt.name,
+          inset: (left: 3pt, right: 3pt, top: 5pt, bottom: 5pt)
+        )
+      )
+      let w = m.width / 1pt
+      let h = m.height / 1pt
+      let cx = (x0 + x1) / 2
+      let xl = cx - w / 2
+      let xr = cx + w / 2
+
+      y -= h / 2
+      draw.line((x0, y), (xl, y))
+      draw.line((xr, y), (x1, y))
+      y -= 3
+      draw.line((x0, y), (xl, y))
+      draw.line((xr, y), (x1, y))
+      draw.content(
+        ((x0 + x1) / 2, y + 1.5),
+        elmt.name,
+        anchor: "center",
+        padding: (5pt, 3pt),
+        frame: "rect"
+      )
+      y -= h / 2
+      y -= Y-SPACE
     }
   }