added alt/else, loops and other group shortcuts

src/renderer.typ

@@ -242,6 +242,7 @@
 
   let draw-seq = sequence.render.with(pars-i, x-pos, participants)
   let draw-group = group.render.with()
+  let draw-else = group.render-else.with()
   let draw-sep = separator.render.with(x-pos)
   let draw-par = participant.render.with(x-pos)
   let draw-note = note.render.with(pars-i, x-pos)
@@ -283,6 +284,9 @@
         if g.at(1).max-i == elmt.max-i { g.at(3) += 1 }
         g
       })
+      if elmt.grp-type == "alt" {
+        elmt.insert("elses", ())
+      }
       groups.push((y, elmt, 0, 0))
       y -= m.height / 1pt
     
@@ -294,6 +298,21 @@
       let x1 = x-pos.at(group.max-i) + end-lvl * 10 + 20
       shapes += draw-group(x0, x1, start-y, y, group)
 
+      if group.grp-type == "alt" {
+        for (else-y, else-elmt) in group.elses {
+          shapes += draw-else(x0, x1, else-y, else-elmt)
+        }
+      }
+
+    // Alt's elses -> reserve space for label + store position
+    } else if elmt.type == "else" {
+      y -= Y-SPACE
+      let m = measure(text([\[#elmt.desc\]], weight: "bold", size: .8em))
+      groups.last().at(1).elses.push((
+        y, elmt
+      ))
+      y -= m.height / 1pt
+
     // Separator
     } else if elmt.type == "sep" {
       let shps