support colour reinsert after resets, switch to intrinsics by default

lib/emitter.ml

@@ -11,7 +11,8 @@ let write_ansi a =
   and string_of_colour ?(bg = false) c =
     let prefix = if bg then "4" else "3" and si = string_of_int in
     c |> function
-    | Intrinsic i -> prefix ^ si i
+    | Intrinsic i ->
+        if i <= 8 then prefix ^ si i else (if bg then "10" else "9") ^ si (i - 8)
     | Simple i -> prefix ^ "8;5;" ^ si i
     | RGB (r, g, b) -> prefix ^ "8;2;" ^ si r ^ ";" ^ si g ^ ";" ^ si b
   in
@@ -35,18 +36,21 @@ let flush t =
     t.pos <- 0)
 
 let serialise t chunk =
-  let input =
-    match chunk with
-    | Text s -> s
-    | Separator s -> s
-    | Delimiter s -> s
-    | Ansi a -> write_ansi a
-  and sz = Bytes.length t.buf in
-  let input_sz = String.length input in
-  if t.pos + input_sz > sz then flush t;
-  if input_sz > sz then print_string input
-  else (
-    Bytes.blit_string input 0 t.buf t.pos input_sz;
-    t.pos <- t.pos + input_sz)
+  if chunk != Empty then (
+    let input =
+      match chunk with
+      | Text s -> s
+      | Separator s -> s
+      | Delimiter s -> s
+      | Ansi a -> write_ansi a
+      | Empty -> assert false
+    and sz = Bytes.length t.buf in
+    let input_sz = String.length input in
+    if t.pos + input_sz > sz then flush t;
+    if input_sz > sz then print_string input
+    else (
+      Bytes.blit_string input 0 t.buf t.pos input_sz;
+      t.pos <- t.pos + input_sz))
+  else ()
 
 let create = { buf = Bytes.create 4096; pos = 0 }