add iso216 card sheets

cards_a6_a4sheet.typ

@@ -0,0 +1,9 @@
+#{
+  import "common.typ"
+
+  let options = json("cache/options.json")
+  let cards = options.cards
+  let args = options.args
+
+  common.iso216_a_card_sheets(4, 6, args, cards)
+}

common.typ

@@ -114,13 +114,17 @@
   )
 }
 
-#let card_sheets(width, height, margin, args, cards) = {
-  let content_fn = if args.no_content {
+#let get_content_fn(args) = {
+  if args.no_content {
     _ => []
   } else {
     import "cache/content/content.typ"
     content.content
   }
+}
+
+#let card_sheets(width, height, margin, args, cards) = {
+  let content_fn = get_content_fn()
 
   for (idx, card) in cards.enumerate() {
     let row = calc.rem(idx + args.skip, 2)
@@ -136,3 +140,60 @@
     )
   }
 }
+
+// It would be nice to calculate this but the rounding makes no sense,
+// hardcode it.
+#let iso216_lengths = (
+  1189mm,
+  841mm,
+  594mm,
+  420mm,
+  297mm,
+  210mm,
+  148mm,
+  105mm,
+  74mm,
+  52mm,
+  37mm,
+  26mm
+)
+
+#let iso216_a_size(format) = {
+  (iso216_lengths.at(format), iso216_lengths.at(format + 1))
+}
+
+// Pack together smaller ISO 216 A-series cards to make a full-size card.
+// Useful to print on a large printer or plotter then use a paper cutter
+#let iso216_a_card_sheets(page_format, card_format, args, cards) = {
+  let is_landscape = calc.even(card_format - page_format)
+  let (num_rows, num_cols) = if is_landscape {
+    let num = calc.pow(2, (card_format - page_format) / 2)
+    (num, num)
+  } else {
+    let cols = calc.pow(2, (card_format - 1 - page_format) / 2)
+    (cols * 2, cols)
+  }
+
+  let (page_long, page_short) = iso216_a_size(page_format)
+  set page(margin: 0mm, width: page_short, height: page_long, flipped: is_landscape)
+
+  let (card_long, card_short) = iso216_a_size(card_format)
+  let content_fn = get_content_fn(args)
+  
+  for (idx, card) in cards.enumerate() {
+    if idx != 0 and calc.rem(idx + args.skip, num_rows * num_cols) == 0 {
+      pagebreak()
+    }
+
+    let offset_idx = idx + args.skip
+    let col = calc.rem(offset_idx, num_cols)
+    let row = calc.rem(calc.floor(offset_idx / num_cols), num_rows)
+    
+    place(
+      top + left,
+      dx: col * card_long,
+      dy: row * card_short,
+      postcard_block(card_long, card_short, content_fn, args, card)
+    )
+  }
+}