added gaps

gallery/example1.typ

@@ -53,4 +53,16 @@ Alice <-- Bob: Another authentication Response
   _sep("Repetition")
   _seq("Alice", "Bob", comment: "Another authentication Request")
   _seq("Bob", "Alice", comment: "another authentication Response", dashed: true)
+})
+
+#chronos.diagram({
+  import "/src/diagram.typ": *
+  _seq("Alice", "Bob", comment: "message 1")
+  _seq("Bob", "Alice", comment: "ok", dashed: true)
+  _gap()
+  _seq("Alice", "Bob", comment: "message 2")
+  _seq("Bob", "Alice", comment: "ok", dashed: true)
+  _gap(size: 45)
+  _seq("Alice", "Bob", comment: "message 3")
+  _seq("Bob", "Alice", comment: "ok", dashed: true)
 })

src/diagram.typ

@@ -55,6 +55,13 @@
   ),)
 }
 
+#let _gap(size: 20) = {
+  return ((
+    type: "gap",
+    size: size
+  ),)
+}
+
 #let diagram(elements) = {
   let participants = ()
   let elmts = elements

src/renderer.typ

@@ -4,6 +4,7 @@
 #let Y-SPACE = 10
 #let PAR-PAD = (5pt, 3pt)
 #let PAR-SPACE = 10
+#let COMMENT-PAD = 8
 
 
 #let get-columns-width(participants, elements) = {
@@ -38,7 +39,7 @@
     let m = measure(cell.cell)
     widths.at(cell.i1) = calc.max(
       widths.at(cell.i1),
-      m.width / 1pt
+      m.width / 1pt + COMMENT-PAD
     )
   }
 
@@ -133,9 +134,13 @@
       )
 
       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(
-          (calc.min(x1, x2), y),
+          (x, y),
           elmt.comment,
           anchor: "south-west",
           padding: 3pt
@@ -200,6 +205,8 @@
       )
       y -= h / 2
       y -= Y-SPACE
+    } else if elmt.type == "gap" {
+      y -= elmt.size
     }
   }