Cleanup, reduce Lwd.set calls

We don't use position, and we don't calculate width yet.

prompt.ml

@@ -2,13 +2,14 @@ open Nottui
 open Notty
 
 type t = {
+  quit : unit -> unit;
   message : string -> unit;
   cursor : Rp.Cursor.cursor;
 }
 
-let make message =
+let make quit message =
   let cursor = Rp.Cursor.create Rp.empty 0 in
-  { message; cursor }
+  { quit; message; cursor }
 
 let map_cursor f state =
   { state with cursor = f state.cursor }
@@ -63,7 +64,9 @@ module User_prompt = struct
     let text, position =
       Utils.render_cursor ~width:(max 0 (w - 3)) state.cursor
     in
-    Lwd.set cursor (position + 1, y);
+    let new_cursor = (position + 1, y) in
+    if new_cursor <> (Lwd.peek cursor) then
+      Lwd.set cursor new_cursor;
     I.hcat [ I.char A.empty ' ' 1 1 ; text ]
 end
 
@@ -104,15 +107,21 @@ let handler ~hook state = function
     state.message msg;
     hook { state with cursor = Rp.Cursor.create Rp.empty 0 };
     `Handled
+  | `ASCII ('C'..'D'), [`Ctrl] ->
+    state.quit ();
+    `Handled
   | _ -> `Unhandled
 
-let make ~message cursor =
+let make ~quit ~message cursor =
   let ( let* ) x f = Lwd.bind x ~f in
   let ( let+ ) x f = Lwd.map ~f x in
   let ( and+ ) = Lwd.map2 ~f:(fun x y -> (x, y)) in
-  let state = Lwd.var (make message) in
+  let state = Lwd.var (make quit message) in
   let position = Lwd.var (0, 0) in
-  let hook = Lwd.set state in
+  let hook state' =
+    if (Lwd.peek state).cursor != state'.cursor then
+      Lwd.set state state'
+  in
   let update_prompt state (y, w) =
     let user = User_prompt.render ~cursor ~y ~w state in
     Ui.keyboard_area (handler ~hook state) (Ui.atom user)

rope.ml

@@ -162,7 +162,7 @@ module Make (S : STRING) (C : CONTROL) = struct
     if len = 0 then empty else mksub ofs stop t
 
   let rec safe_iter_range f i n = function
-    | Str (s, ofs, _) -> S.iter_range f s (ofs + i) n
+    | Str (s, ofs, _) -> S.iter_range f s (max 0 (ofs + i)) n
     | App (t1, t2, _, _) ->
         let n1 = length t1 in
         if i + n <= n1 then safe_iter_range f i n t1

unikernel.ml

@@ -43,10 +43,15 @@ module Main (_ : Mirage_random.S) (T : Mirage_time.S) (M : Mirage_clock.MCLOCK)
         let msg = Message.make ~nickname:username m in
         Lwd.set buffer_var (Rb.push buffer msg; buffer);
       in
-      Rb.push buffer (Message.msgf "Welcome, %s!" username);
+      let quit () =
+        let msg = Message.msgf "%s tried to quit, but it is not implemented" username in
+        Lwd.set buffer_var (Rb.push buffer msg; buffer);
+      in
+      Lwd.set buffer_var
+        (Rb.push buffer (Message.msgf "Welcome, %s!" username); buffer);
       let ui =
         let ( let* ) x f = Lwd.bind x ~f in
-        let* prompt = Prompt.make ~message cursor in
+        let* prompt = Prompt.make ~quit ~message cursor in
         let* window = Window.make buffer_var in
         Lwd.return (Nottui.Ui.vcat [window; prompt])
       in

window.ml

@@ -1,7 +1,7 @@
 open Nottui
 open Notty
 
-type t = { w : int; h : int; p : int }
+type t = { w : int; h : int; }
 
 let render_message ~width ~width_nicknames msg =
   (* (* FIXME: split doesn't work *)
@@ -9,6 +9,7 @@ let render_message ~width ~width_nicknames msg =
     max 1 (width - width_nicknames - 1)
   in
   let message = Message.split_at ~len:width_message msg in *)
+  let _ = width in
   let message = [Message.message msg] in
   let color = A.white in
   let rest =
@@ -33,8 +34,8 @@ let width_nicknames msgs =
   let f msg acc = max (String.length (Message.nickname msg)) acc in
   Rb.iter ~f msgs 0
  
-let render { w; h; p } msgs =
-  let idx = ref (Rb.length msgs - 1 - p) in
+let render { w; h } msgs =
+  let idx = ref (Rb.length msgs - 1) in
   let image = ref I.empty in
   let message = ref I.empty in
   let width_nicknames = width_nicknames msgs in
@@ -50,27 +51,22 @@ let render { w; h; p } msgs =
   done;
   Ui.atom (I.vsnap ~align:`Bottom h !image)
 
-let handler ~hook:_ _state _buffer _key = `Unhandled
-
 let make w =
   let ( let* ) x f = Lwd.bind ~f x in
   let ( let+ ) x f = Lwd.map ~f x in
   let ( and+ ) = Lwd.map2 ~f:(fun x y -> (x, y)) in
 
-  let state = Lwd.var { w = 0; h = 0; p = 0 } in
-  let hook = Lwd.set state in
+  let state = Lwd.var { w = 0; h = 0 } in
 
   let* document =
     let+ state = Lwd.get state
     and+ buffer = Lwd.get w in
-    Ui.keyboard_area
-      (handler ~hook state buffer)
-      (render state buffer)
+    render state buffer
   in
 
   let update_size ~w ~h =
     let state' = Lwd.peek state in
-    if state'.w <> w || state'.h <> h then Lwd.set state { state' with w; h }
+    if state'.w <> w || state'.h <> h then Lwd.set state { w; h }
   in
 
   let measure_size document =