CoqIDE: move cmd_stack to a separate module: Document

The idea is to move the logic related to document handling
to a separate module that can be tested by fake_ide too.
CoqOps should "only" interface Document with the GtkTextBuffer.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16870 85f007b7-540e-0410-9357-904b9bb8a0f7

4 files changed, 315 insertions, 236 deletions

diff --git a/Makefile.build b/Makefile.build
index 99ef062b9..964a4694f 100644
--- a/Makefile.build
+++ b/Makefile.build
@@ -541,9 +541,13 @@ $(COQDOC): $(patsubst %.cma,%$(BESTLIB),$(COQDOCCMO:.cmo=$(BESTOBJ)))
 # fake_ide : for debugging or test-suite purpose, a fake ide simulating
 # a connection to coqtop -ideslave
 
-$(FAKEIDE): lib/clib$(BESTLIB) lib/xml_lexer$(BESTOBJ) lib/xml_parser$(BESTOBJ) lib/xml_printer$(BESTOBJ) tools/fake_ide$(BESTOBJ)
+tools/fake_ide.cmo: COND_BYTEFLAGS+=-I ide
+
+tools/fake_ide.cmx: COND_OPTFLAGS+=-I ide
+
+$(FAKEIDE): lib/clib$(BESTLIB) lib/xml_lexer$(BESTOBJ) lib/xml_parser$(BESTOBJ) lib/xml_printer$(BESTOBJ) ide/document$(BESTOBJ) tools/fake_ide$(BESTOBJ)
 	$(SHOW)'OCAMLBEST -o $@'
-	$(HIDE)$(call bestocaml,,str unix)
+	$(HIDE)$(call bestocaml,-I ide,str unix)
 
 # votour: a small vo explorer (based on the checker)
 
diff --git a/ide/coqOps.ml b/ide/coqOps.ml
index e9f29fba1..1246d3159 100644
--- a/ide/coqOps.ml
+++ b/ide/coqOps.ml
@@ -30,13 +30,11 @@ module SentenceId : sig
     mutable flags : flag list;
     mutable tooltips : (int * int * string lazy_t) list;
     edit_id : int;
-    mutable state_id : Stateid.t option;
   }
 
   val mk_sentence :
     start:GText.mark -> stop:GText.mark -> flag list -> sentence
 
-  val assign_state_id : sentence -> Stateid.t -> unit
   val set_flags : sentence -> flag list -> unit
   val add_flag : sentence -> flag -> unit
   val has_flag : sentence -> mem_flag -> bool
@@ -46,7 +44,8 @@ module SentenceId : sig
   val find_all_tooltips : sentence -> int -> string lazy_t list
   val add_tooltip : sentence -> int -> int -> string lazy_t -> unit
 
-  val dbg_to_string : GText.buffer -> sentence -> string
+  val dbg_to_string :
+    GText.buffer -> bool -> Stateid.t option -> sentence -> Pp.std_ppcmds
 
 end = struct
 
@@ -56,7 +55,6 @@ end = struct
     mutable flags : flag list;
     mutable tooltips : (int * int * string lazy_t) list;
     edit_id : int;
-    mutable state_id : Stateid.t option;
   }
 
   let id = ref 0
@@ -65,36 +63,32 @@ end = struct
     stop = stop;
     flags = flags;
     edit_id = !id;
-    state_id = None;
     tooltips = [];
   }
   let hidden_edit_id () = decr id; !id
 
-  let assign_state_id s id =
-    assert(s.state_id = None);
-    assert(id <> Stateid.dummy);
-    s.state_id <- Some id
   let set_flags s f = s.flags <- f
   let add_flag s f = s.flags <- CList.add_set f s.flags
   let has_flag s mf =
     List.exists (fun f -> mem_flag_of_flag f = mf) s.flags
   let remove_flag s mf =
     s.flags <- List.filter (fun f -> mem_flag_of_flag f <> mf) s.flags
-  let same_sentence s1 s2 = s1.edit_id = s2.edit_id && s1.state_id = s2.state_id
+  let same_sentence s1 s2 = s1.edit_id = s2.edit_id
   let find_all_tooltips s off =
     CList.map_filter (fun (start,stop,t) ->
       if start <= off && off <= stop then Some t else None)
     s.tooltips
   let add_tooltip s a b t = s.tooltips <- (a,b,t) :: s.tooltips
 
-  let dbg_to_string (b : GText.buffer) s =
+  let dbg_to_string (b : GText.buffer) focused id s =
     let ellipsize s =
             Str.global_replace (Str.regexp "^[\n ]*") ""
         (if String.length s > 20 then String.sub s 0 17 ^ "..."
          else s) in
-    Printf.sprintf "[%3d,%3s](%5d,%5d) %s [%s] %s"
+    Pp.str (Printf.sprintf "%s[%3d,%3s](%5d,%5d) %s [%s] %s"
+      (if focused then "*" else " ")
       s.edit_id
-      (Stateid.to_string (Option.default Stateid.dummy s.state_id))
+      (Stateid.to_string (Option.default Stateid.dummy id))
       (b#get_iter_at_mark s.start)#offset
       (b#get_iter_at_mark s.stop)#offset
       (ellipsize
@@ -103,7 +97,7 @@ end = struct
       (ellipsize
         (String.concat ","
           (List.map (fun (a,b,t) ->
-             Printf.sprintf "<%d,%d> %s" a b (Lazy.force t)) s.tooltips)))
+             Printf.sprintf "<%d,%d> %s" a b (Lazy.force t)) s.tooltips))))
 
 
 end
@@ -137,6 +131,8 @@ object
   method destroy : unit -> unit
 end
 
+module Doc = Document
+
 class coqops
   (_script:Wg_ScriptView.script_view)
   (_pv:Wg_ProofView.proof_view)
@@ -149,7 +145,7 @@ object(self)
   val proof = _pv
   val messages = _mv
 
-  val cmd_stack = Document.create ()
+  val document : sentence Doc.document = Doc.create ()
 
   val mutable initial_state = Stateid.initial
 
@@ -175,16 +171,16 @@ object(self)
           let marks = iter#marks in
           if marks = [] then aux iter#backward_char
           else
-            let mem_marks s _ =
+            let mem_marks _ _ s =
               List.exists (fun m ->
                 Gobject.get_oid m =
                 Gobject.get_oid (buffer#get_mark s.start)) marks in
-            try Document.find mem_marks cmd_stack
+            try Doc.find document mem_marks 
             with Not_found -> aux iter#backward_char in
         aux iter in
       let ss =
-        find_all_tooltips s
-          (iter#offset - (buffer#get_iter_at_mark s.start)#offset) in
+        find_all_tooltips s.Doc.data
+          (iter#offset - (buffer#get_iter_at_mark s.Doc.data.start)#offset) in
       let msg = String.concat "\n" (CList.uniquize (List.map Lazy.force ss)) in
       GtkBase.Tooltip.set_icon_from_stock tooltip `INFO `BUTTON;
       script#misc#set_tooltip_markup ("<tt>" ^ msg ^ "</tt>")
@@ -197,26 +193,19 @@ object(self)
     feedback_timer.Ideutils.kill ()
 
   method private print_stack =
-    Minilib.log "cmd_stack:";
-    let top, mid, bot = Document.to_lists cmd_stack in
-    Minilib.log "--start--";
-    List.iter (fun s -> Minilib.log(dbg_to_string buffer s)) top;
-    if Document.focused cmd_stack then Minilib.log "----";
-    List.iter (fun s -> Minilib.log(dbg_to_string buffer s)) mid;
-    if Document.focused cmd_stack then Minilib.log "----";
-    List.iter (fun s -> Minilib.log(dbg_to_string buffer s)) bot;
-    Minilib.log "--stop--"
+    Minilib.log "document:";
+    Minilib.log (Pp.string_of_ppcmds (Doc.print document (dbg_to_string buffer)))
 
   method private enter_focus start stop to_id tip =
-    if Document.focused cmd_stack then begin
+    if Doc.focused document then begin
       self#exit_focus tip
     end;
-    let at id s = s.state_id = Some id in
+    let at id s = s.Doc.state_id = Some id in
     self#print_stack;
     Minilib.log("Focusing "^Stateid.to_string start^" "^Stateid.to_string stop);
-    Document.focus cmd_stack ~cond_top:(at start) ~cond_bot:(at stop);
+    Doc.focus document ~cond_top:(at start) ~cond_bot:(at stop);
     self#print_stack;
-    let qed_s = Document.tip cmd_stack in
+    let qed_s = Doc.tip_data document in
     buffer#apply_tag Tags.Script.read_only
       ~start:((buffer#get_iter_at_mark qed_s.start)#forward_find_char
         (fun c -> not(Glib.Unichar.isspace c)))
@@ -227,15 +216,15 @@ object(self)
   method private exit_focus newtip =
     self#print_stack;
     Minilib.log "Unfocusing";
-    Document.unfocus cmd_stack;
+    Doc.unfocus document;
     self#print_stack;
-    if (Some newtip <> (Document.tip cmd_stack).state_id) then begin
+    if (Some newtip <> (Doc.tip document).Doc.state_id) then begin
       Minilib.log ("Cutting tip to " ^ Stateid.to_string newtip);
-      let until _ id _ _ = id = Some newtip in
+      let until id _ _ = id = Some newtip in
       let n, _, _, seg = self#segment_to_be_cleared until in
       self#cleanup n seg
     end;
-    let where = buffer#get_iter_at_mark (Document.tip cmd_stack).stop in
+    let where = buffer#get_iter_at_mark (Doc.tip_data document).stop in
     buffer#move_mark ~where (`NAME "start_of_input");
     buffer#move_mark ~where:buffer#end_iter (`NAME "stop_of_input")
 
@@ -281,7 +270,8 @@ object(self)
     Coq.bind (Coq.seq action query) next
 
   method private mark_as_needed sentence =
-    Minilib.log("Marking " ^ dbg_to_string buffer sentence);
+    Minilib.log("Marking " ^
+      Pp.string_of_ppcmds (dbg_to_string buffer false None sentence));
     let start = buffer#get_iter_at_mark sentence.start in
     let stop = buffer#get_iter_at_mark sentence.stop in
     let to_process = Tags.Script.to_process in
@@ -327,34 +317,34 @@ object(self)
       let msg = Queue.pop feedbacks in
       let id = msg.id in
       let sentence =
-        let finder s _ =
-          match s.state_id, id with
-          | Some id', State id when id = id' -> Some s
-          | _, Edit id when id = s.edit_id -> Some s
+        let finder _ state_id s =
+          match state_id, id with
+          | Some id', State id when Stateid.equal id id' -> Some (state_id, s)
+          | _, Edit id when id = s.edit_id -> Some (state_id, s)
           | _ -> None in
-        try Some (Document.find_map finder cmd_stack)
+        try Some (Doc.find_map document finder)
         with Not_found -> None in
-      let log s sentence =
+      let log s state_id =
         Minilib.log ("Feedback " ^ s ^ " on " ^ Stateid.to_string
-          (Option.default Stateid.dummy sentence.state_id)) in
+          (Option.default Stateid.dummy state_id)) in
       begin match msg.content, sentence with
-      | AddedAxiom, Some sentence ->
-          log "AddedAxiom" sentence;
+      | AddedAxiom, Some (id,sentence) ->
+          log "AddedAxiom" id;
           remove_flag sentence `PROCESSING;
           remove_flag sentence `ERROR;
           add_flag sentence `UNSAFE;
           self#mark_as_needed sentence
-      | Processed, Some sentence ->
-          log "Processed" sentence;
+      | Processed, Some (id,sentence) ->
+          log "Processed" id;
           remove_flag sentence `PROCESSING;
           remove_flag sentence `ERROR;
           self#mark_as_needed sentence
-      | GlobRef(loc, filepath, modpath, ident, ty), Some sentence ->
-          log "GlobRef" sentence;
+      | GlobRef(loc, filepath, modpath, ident, ty), Some (id,sentence) ->
+          log "GlobRef" id;
           self#attach_tooltip sentence loc
             (Printf.sprintf "%s %s %s" filepath ident ty)
-      | ErrorMsg(loc, msg), Some sentence ->
-          log "ErrorMsg" sentence;
+      | ErrorMsg(loc, msg), Some (id,sentence) ->
+          log "ErrorMsg" id;
           remove_flag sentence `PROCESSING;
           add_flag sentence (`ERROR msg);
           self#mark_as_needed sentence;
@@ -367,9 +357,9 @@ object(self)
 
       | _ ->
           if sentence <> None then Minilib.log "Unsupported feedback message"
-          else if Document.is_empty cmd_stack then ()
+          else if Doc.is_empty document then ()
           else
-            match id, (Document.tip cmd_stack).state_id with
+            match id, (Doc.tip document).Doc.state_id with
             | Edit _, _ -> ()
             | State id1, Some id2 when Stateid.newer_than id2 id1 -> ()
             | _ -> Queue.add msg feedbacks (* Put back into the queue *)
@@ -419,15 +409,15 @@ object(self)
       condition returns true; it is fed with the number of phrases read and the
       iters enclosing the current sentence. *)
   method private fill_command_queue until queue =
-    let rec loop len iter =
+    let rec loop iter =
       match Sentence.find buffer iter with
       | None -> ()
       | Some (start, stop) ->
-        if until len start stop then begin
+        if until start stop then begin
           ()
         end else if start#has_tag Tags.Script.processed then begin
           Queue.push (`Skip (start, stop)) queue;
-          loop len stop
+          loop stop
         end else begin
           buffer#apply_tag Tags.Script.to_process ~start ~stop;
           (* Check if this is a comment *)
@@ -440,10 +430,10 @@ object(self)
               ~stop:(`MARK (buffer#create_mark stop))
               (if is_comment then [`COMMENT] else []) in
           Queue.push (`Sentence sentence) queue;
-          if not stop#is_end then loop (succ len) stop
+          if not stop#is_end then loop stop
         end
     in
-    loop 0 self#get_start_of_input
+    loop self#get_start_of_input
 
   method private discard_command_queue queue =
     while not (Queue.is_empty queue) do
@@ -474,9 +464,9 @@ object(self)
       queue)
     in
     let tip =
-      try Document.fold_until (fun () -> function
-          | { state_id = Some id } -> Stop id
-          | _ -> Next ()) () cmd_stack
+      try Doc.fold_until document () (fun () -> function
+          | Some id -> fun _ -> Stop id
+          | _ -> fun _ -> Next ())
       with Not_found -> initial_state in
     Coq.bind action (fun queue ->
     let rec loop tip topstack =
@@ -485,18 +475,19 @@ object(self)
         let () = script#recenter_insert in
         match topstack with
         | [] -> self#show_goals
-        | s :: _ -> self#backtrack_to_iter (buffer#get_iter_at_mark s.start)
+        | s :: _ ->
+           self#backtrack_to_iter (buffer#get_iter_at_mark s.Doc.data.start)
       else
         match Queue.pop queue, topstack with
         | `Skip(start,stop), [] -> assert false
         | `Skip(start,stop), s :: topstack ->
-            assert(start#equal (buffer#get_iter_at_mark s.start));
-            assert(stop#equal (buffer#get_iter_at_mark s.stop));
+            assert(start#equal (buffer#get_iter_at_mark s.Doc.data.start));
+            assert(stop#equal (buffer#get_iter_at_mark s.Doc.data.stop));
             loop tip topstack
         | `Sentence sentence, _ :: _ -> assert false
         | `Sentence sentence, [] ->
         add_flag sentence `PROCESSING;
-        Document.push sentence cmd_stack;
+        Doc.push document sentence;
         if has_flag sentence `COMMENT then
           let () = remove_flag sentence `PROCESSING in
           let () = self#commit_queue_transaction sentence in
@@ -508,21 +499,21 @@ object(self)
             Coq.add ~logger:push_msg ((phrase,sentence.edit_id),(tip,verbose))in
           let next = function
           | Good (id, (Util.Inl (* NewTip *) (), msg)) ->
-              assign_state_id sentence id;
+              Doc.assign_tip_id document id;
               push_msg Notice msg;
               self#commit_queue_transaction sentence;
               loop id []
           | Good (id, (Util.Inr (* Unfocus *) tip, msg)) ->
-              assign_state_id sentence id;
-              let topstack, _, _ = Document.to_lists cmd_stack in
+              Doc.assign_tip_id document id;
+              let topstack, _, _ = Doc.to_lists document in
               self#exit_focus tip;
               push_msg Notice msg;
               self#mark_as_needed sentence;
               if Queue.is_empty queue then loop tip []
               else loop tip (List.rev topstack)
           | Fail (id, loc, msg) ->
-              let sentence = Document.pop cmd_stack in
-              self#process_interp_error queue sentence loc msg id
+              let sentence = Doc.pop document in
+              self#process_interp_error queue sentence.Doc.data loc msg id
           in
           Coq.bind query next
     in
@@ -532,7 +523,7 @@ object(self)
    let next = function
      | Good _ ->
          messages#clear;
-         messages#push Info "Document checked";
+         messages#push Info "Doc checked";
          Coq.return ()
      | Fail x -> self#handle_failure x in
    Coq.bind (Coq.status ~logger:messages#push true) next
@@ -541,8 +532,8 @@ object(self)
 
   method get_n_errors = 
     List.fold_left
-      (fun n s -> if has_flag s `ERROR then n+1 else n)
-      0 (Document.to_list cmd_stack)
+      (fun n s -> if has_flag s.Doc.data `ERROR then n+1 else n)
+      0 (Doc.to_list document)
 
   method get_errors =
     let extract_error s =
@@ -550,19 +541,19 @@ object(self)
       | `ERROR msg -> (buffer#get_iter_at_mark s.start)#line + 1, msg
       | _ -> assert false in
     CList.map_filter (fun s ->
-      if has_flag s `ERROR then Some (extract_error s)
+      if has_flag s.Doc.data `ERROR then Some (extract_error s.Doc.data)
       else None)
-      (Document.to_list cmd_stack)
+      (Doc.to_list document)
 
   method process_next_phrase =
-    let until len start stop = 1 <= len in
+    let until = let len = ref 0 in fun _ _ -> incr len; !len > 1 in
     let next () =
       buffer#place_cursor ~where:self#get_start_of_input; Coq.return ()
     in
     Coq.bind (self#process_until until true) next
 
   method private process_until_iter iter =
-    let until len start stop =
+    let until start stop =
       if prefs.Preferences.stop_before then stop#compare iter > 0
       else start#compare iter >= 0
     in
@@ -573,33 +564,33 @@ object(self)
 
   (* finds the state_id and if it an unfocus is needed to reach it *)
   method private find_id until =
+    let focused = Doc.focused document in
     try
-      Document.find_map
-        (function
-          | { start; stop; state_id = Some id } -> fun b ->
-              if until 0 (Some id) start stop then
-                Some (id, if Document.focused cmd_stack then not b else false)
-              else
-                None
-          | { start; stop; state_id = None } -> fun _ -> None)
-      cmd_stack
-    with Not_found -> initial_state, Document.focused cmd_stack
+      Doc.find_map document (fun b ->
+        function
+        | Some id -> fun { start; stop } ->
+           if until (Some id) start stop then
+             Some (id, if focused then not b else false)
+           else
+             None
+        | None -> fun { start; stop } -> None)
+    with Not_found -> initial_state, focused 
 
   method private segment_to_be_cleared until =
-    let finder (n, found, zone) ({ start; stop; state_id } as sentence) =
-      let found = found || until n state_id start stop in
+    let finder (n, found, zone) state_id ({ start; stop } as sentence) =
+      let found = found || until state_id start stop in
       match found, state_id with
       | true, Some id -> Stop (n, id, Some sentence, zone)
       | _ -> Next (n + 1, found, sentence :: zone) in
-    try Document.fold_until finder (0, false, []) cmd_stack
+    try Doc.fold_until document (0, false, []) finder
     with Not_found ->
-            Minilib.log "ALL";
-      Document.length cmd_stack, initial_state,
-      None, List.rev (Document.to_list cmd_stack)
+            Minilib.log "XXX ALL XXX";
+      Doc.length document, initial_state,
+      None, List.rev (List.map (fun x -> x.Doc.data) (Doc.to_list document))
 
   method private cleanup n seg =
     Minilib.log("Clean "^string_of_int n^" "^string_of_int(List.length seg));
-    for i = 1 to n do ignore(Document.pop cmd_stack) done;
+    for i = 1 to n do ignore(Doc.pop document) done;
     if seg <> [] then begin
       let start = buffer#get_iter_at_mark (CList.hd seg).start in
       let stop = buffer#get_iter_at_mark (CList.last seg).stop in
@@ -638,7 +629,7 @@ object(self)
           if unfocus_needed then self#exit_focus to_id
           else begin
             let n, to_id, sentence, seg =
-              self#segment_to_be_cleared (fun _ id _ _ -> id = Some to_id) in
+              self#segment_to_be_cleared (fun id _ _ -> id = Some to_id) in
             self#cleanup n seg
           end;
           conclusion ()
@@ -647,19 +638,19 @@ object(self)
           else begin
             self#enter_focus start_id stop_id to_id tip;
             let n, to_id, sentence, seg =
-              self#segment_to_be_cleared (fun _ id _ _ -> id = Some to_id) in
+              self#segment_to_be_cleared (fun id _ _ -> id = Some to_id) in
             self#cleanup n seg
           end;
           conclusion ()
       | Fail (safe_id, loc, msg) ->
           if loc <> None then messages#push Error "Fixme LOC";
           messages#push Error msg;
-          undo (fun _ id _ _ -> id = Some safe_id))
+          undo (fun id _ _ -> id = Some safe_id))
     in
       undo until)
 
   method private backtrack_to_iter ?move_insert iter =
-    let until _ _ _ stop = iter#compare (buffer#get_iter_at_mark stop) >= 0 in
+    let until _ _ stop = iter#compare (buffer#get_iter_at_mark stop) >= 0 in
     self#backtrack_until ?move_insert until
 
   method handle_failure (safe_id, (loc : (int * int) option), msg) =
@@ -669,12 +660,13 @@ object(self)
     ignore(self#process_feedback ());
     Coq.seq
       (self#backtrack_until ~move_insert:false
-        (fun _ id _ _ -> id = Some safe_id))
+        (fun id _ _ -> id = Some safe_id))
       (Coq.lift (fun () ->
         script#scroll_mark_onscreen (`NAME "start_of_input")))
 
   method backtrack_last_phrase =
-    let until n _ _ _ = n >= 1 in
+    let id = (Doc.tip document).Doc.state_id in
+    let until sid _ _ = sid <> id in
     messages#clear;
     self#backtrack_until until
 
@@ -710,7 +702,7 @@ object(self)
           ~start:(`MARK (buffer#create_mark start))
           ~stop:(`MARK (buffer#create_mark stop))
           [] in
-      Document.push sentence cmd_stack;
+      Doc.push document sentence;
       messages#clear;
       self#show_goals
     in
@@ -744,11 +736,11 @@ object(self)
     let action () =
       if why = Coq.Unexpected then warning "Coqtop died badly. Resetting.";
       (* clear the stack *)
-      if Document.focused cmd_stack then Document.unfocus cmd_stack;
-      while not (Document.is_empty cmd_stack) do
-        let phrase = Document.pop cmd_stack in
-        buffer#delete_mark phrase.start;
-        buffer#delete_mark phrase.stop
+      if Doc.focused document then Doc.unfocus document;
+      while not (Doc.is_empty document) do
+        let phrase = Doc.pop document in
+        buffer#delete_mark phrase.Doc.data.start;
+        buffer#delete_mark phrase.Doc.data.stop
       done;
       List.iter
         (buffer#remove_tag ~start:buffer#start_iter ~stop:buffer#end_iter)
diff --git a/ide/document.ml b/ide/document.ml
index 96ec05624..9b048320a 100644
--- a/ide/document.ml
+++ b/ide/document.ml
@@ -6,94 +6,153 @@
 (*         *       GNU Lesser General Public License Version 2.1        *)
 (************************************************************************)
 
-exception Empty = Stack.Empty
+exception Empty
 
-type 'a t = {
-  mutable stack : 'a list;
-  mutable context : ('a list * 'a list) option
-}
+let invalid_arg s = raise (Invalid_argument ("Document."^s))
+
+type 'a sentence = { mutable state_id : Stateid.t option; data : 'a }
 
+type id = Stateid.t
+type 'a document = {
+  mutable stack : 'a sentence list;
+  mutable context : ('a sentence list * 'a sentence list) option
+}
+  
 let create () = { stack = []; context = None }
 
-let push x s = s.stack <- x :: s.stack
-
-let pop = function
-  | { stack = [] } -> raise Stack.Empty
-  | { stack = x::xs } as s -> s.stack <- xs; x
+(* Invariant, only the tip is a allowed to have state_id = None *)
+let invariant l = l = [] || (List.hd l).state_id <> None
 
 let tip = function
-  | { stack = [] } -> raise Stack.Empty
-  | { stack = x::_ } -> x
+  | { stack = [] } -> raise Empty
+  | { stack = { state_id = Some id }::_ } -> id
+  | { stack = { state_id = None }::_ } -> invalid_arg "tip"
+  
+let tip_data = function
+  | { stack = [] } -> raise Empty
+  | { stack = { data }::_ } -> data
+
+let push d x =
+  assert(invariant d.stack);
+  d.stack <- { data = x; state_id = None } :: d.stack
 
-let to_list = function
-  | { context = None; stack = s } -> s
-  | { context = Some (a,b); stack = s } -> a @ s @ b
+let pop = function
+  | { stack = [] } -> raise Empty
+  | { stack = { data }::xs } as s -> s.stack <- xs; data
+  
+let focus d ~cond_top:c_start ~cond_bot:c_stop =
+  assert(invariant d.stack);
+  if d.context <> None then invalid_arg "focus";
+  let rec aux (a,s,b) grab = function
+    | [] -> invalid_arg "focus"
+    | { state_id = Some id; data } as x :: xs when not grab ->
+        if c_start id data then aux (a,s,b) true (x::xs)
+        else aux (x::a,s,b) grab xs
+    | { state_id = Some id; data } as x :: xs ->
+        if c_stop id data then List.rev a, List.rev (x::s), xs
+        else aux (a,x::s,b) grab xs 
+    | _ -> assert false in
+  let a, s, b = aux ([],[],[]) false d.stack in
+  d.stack <- s;
+  d.context <- Some (a, b)
+  
+let unfocus = function
+  | { context = None } -> invalid_arg "unfocus"
+  | { context = Some (a,b); stack } as d ->
+       assert(invariant stack);
+       d.context <- None;
+       d.stack <- a @ stack @ b
+  
+let focused { context } = context <> None
 
 let to_lists = function
   | { context = None; stack = s } -> [],s,[]
   | { context = Some (a,b); stack = s } -> a,s,b
 
-let find f s =
-  let a, s, b = to_lists s in
-  try List.find (fun x -> f x false) a with Not_found ->
-  try List.find (fun x -> f x true)  s with Not_found ->
-      List.find (fun x -> f x false) b
-
-let find_map f s =
-  let rec aux b = function
-  | [] -> raise Not_found
-  | x :: xs -> match f x b with None -> aux b xs | Some i -> i
-  in
-  let a, s, b = to_lists s in
-  try aux false a with Not_found -> 
-  try aux true s  with Not_found -> 
-      aux false b
-
-type ('b, 'c) seek = ('b, 'c) CSig.seek = Stop of 'b | Next of 'c
-
-let fold_until f accu s =
-  let rec aux accu = function
-    | [] -> raise Not_found
-    | x :: xs -> match f accu x with Stop x -> x | Next i -> aux i xs in
-  aux accu s.stack
-
+let flat f b = fun x -> f b x.state_id x.data
+
+let find d f =
+  let a, s, b = to_lists d in
+  (
+  try List.find (flat f false) a with Not_found ->
+  try List.find (flat f true)  s with Not_found ->
+      List.find (flat f false) b
+  ).data
+  
+let find_map d f =
+  let a, s, b = to_lists d in
+  try CList.find_map (flat f false) a with Not_found -> 
+  try CList.find_map (flat f true)  s with Not_found -> 
+      CList.find_map (flat f false) b
+  
 let is_empty = function
   | { stack = []; context = None } -> true
   | _ -> false
-
-let iter f = function
-  | { stack = s; context = None } -> List.iter (fun x -> f x true) s
-  | { stack = s; context = Some(a,b) } ->
-        List.iter (fun x -> f x false) a;
-        List.iter (fun x -> f x true)  s;
-        List.iter (fun x -> f x false) b
-
-let clear s = s.stack <- []; s.context <- None
-
-let length = function
-  | { stack = s; context = None } -> List.length s
-  | { stack = s; context = Some(a,b) } ->
-        List.length a + List.length s + List.length b
-
-let focus s ~cond_top:c_start ~cond_bot:c_stop =
-  if s.context <> None then raise (Invalid_argument "CStack.focus");
-  let rec aux (a,s,b) grab = function
-    | [] -> raise (Invalid_argument "CStack.focus")
-    | x::xs when not grab ->
-        if c_start x then aux (a,s,b) true (x::xs)
-        else aux (x::a,s,b) grab xs
-    | x::xs ->
-        if c_stop x then a, x::s, xs
-        else aux (a,x::s,b) grab xs in
-  let a, stack, b = aux ([],[],[]) false s.stack in
-  s.stack <- List.rev stack;
-  s.context <- Some (List.rev a, b)
-
-let unfocus = function
-  | { context = None } -> raise (Invalid_argument "CStack.unfocus")
-  | { context = Some (a,b); stack } as s ->
-       s.context <- None;
-       s.stack <- a @ stack @ b
-
-let focused { context } = context <> None
-
+  
+let context d =
+  let top, _, bot = to_lists d in
+  let pair _ x y = try Option.get x, y with Option.IsNone -> assert false in
+  List.map (flat pair true) top, List.map (flat pair true) bot
+
+let iter d f =
+  let a, s, b = to_lists d in
+  List.iter (flat f false) a;
+  List.iter (flat f true)  s;
+  List.iter (flat f false) b
+  
+let stateid_opt_equal = Option.equal Stateid.equal
+
+let is_in_focus d id =
+  let _, focused, _ = to_lists d in
+  List.exists (fun { state_id } -> stateid_opt_equal state_id (Some id)) focused
+
+let clear d = d.stack <- []; d.context <- None
+  
+let print d f =
+  let top, mid, bot = to_lists d in
+  let open Pp in
+  v 0
+    (List.fold_right (fun i acc -> acc ++ cut() ++ flat f false i) top
+    (List.fold_right (fun i acc -> acc ++ cut() ++ flat f true i)  mid
+    (List.fold_right (fun i acc -> acc ++ cut() ++ flat f false i) bot (mt()))))
+
+let assign_tip_id d id =
+  match d with
+  | { stack = { state_id = None } as top :: _ } -> top.state_id <- Some id
+  | _ -> invalid_arg "assign_tip_id"
+
+let cut_at d id =
+  let aux (n, zone) { state_id; data } =
+    if stateid_opt_equal state_id (Some id) then CSig.Stop (n, List.rev zone)
+    else CSig.Cont (n + 1, data :: zone) in
+  let n, zone = CList.fold_left_until aux (0, []) d.stack in
+  for i = 1 to n do ignore(pop d) done;
+  zone
+
+let find_id d f =
+  let top, focus, bot = to_lists d in
+  let pred = function
+    | { state_id = Some id; data } when f id data -> Some id
+    | _ -> None in
+  try CList.find_map pred top, true with Not_found ->
+  try CList.find_map pred focus, focused d with Not_found ->
+      CList.find_map pred bot, true
+
+let before_tip d =
+  let _, focused, rest = to_lists d in
+  match focused with
+  | _:: { state_id = Some id } :: _ -> id, false
+  | _:: { state_id = None } :: _ -> assert false
+  | [] -> raise Not_found
+  | [_] ->
+      match rest with
+      | { state_id = Some id } :: _ -> id, true
+      | { state_id = None } :: _ -> assert false
+      | [] -> raise Not_found
+
+let fold_all d a f =
+  let top, focused, bot = to_lists d in
+  let a = List.fold_left (fun a -> flat (f a) false) a top in
+  let a = List.fold_left (fun a -> flat (f a) true)  a focused in
+  let a = List.fold_left (fun a -> flat (f a) false) a bot in
+  a
diff --git a/ide/document.mli b/ide/document.mli
index c610f275c..556e1d022 100644
--- a/ide/document.mli
+++ b/ide/document.mli
@@ -6,77 +6,101 @@
 (*         *       GNU Lesser General Public License Version 2.1        *)
 (************************************************************************)
 
-(** Based on OCaml stacks, it is the structure used by CoqIDE to represent
-    the document *)
-
-type 'a t
+(* An 'a document is a structure to hold and manipulate list of sentences.
+   Sentences are equipped with an id = Stateid.t and can carry arbitrary
+   data ('a).
+   
+   When added (push) to the document, a sentence has no id, it has
+   be manually assigned just afterward or the sentence has to be removed
+   (pop) before any other sentence can be pushed.
+   This exception is useful since the process of assigning an id to
+   a sentence may fail (parse error) and an error handler may want to annotate
+   a script buffer with the error message.  This handler needs to find the
+   sentence in question, and it is simpler if the sentence is in the document.
+   Only the functions pop, find, fold_all and find_map can be called on a
+   document with a tip that has no id (and assign_tip_id of course).
+   
+   The document can be focused (non recursively) to a zone.  After that
+   some functions operate on the focused zone only.  When unfocused the
+   context (the part of the document out of focus) is restored.
+*)
 
 exception Empty
-(** Alias for Stack.Empty. *)
-
-val create : unit -> 'a t
-(** Create an empty stack. *)
 
-val push : 'a -> 'a t -> unit
-(** Add an element to a stack. *)
+type 'a document
+type id = Stateid.t
 
-val find : ('a -> bool -> bool) -> 'a t -> 'a
-(** Find the first element satisfying the predicate.
-    The boolean tells If the element is inside the focused zone.
-    @raise Not_found it there is none. *)
+val create : unit -> 'a document
 
-val is_empty : 'a t -> bool
-(** Whether a stack is empty. *)
+(* Functions that work on the focused part of the document ******************* *)
 
-val iter : ('a -> bool -> unit) -> 'a t -> unit
-(** Iterate a function over elements, from the last added one. 
-    The boolean tells If the element is inside the focused zone. *)
+(** The last sentence.  @raise Invalid_argument if tip has no id.  @raise Empty *)
+val tip       : 'a document -> id
 
-val clear : 'a t -> unit
-(** Empty a stack. *)
+(** The last sentence.  @raise Empty *)
+val tip_data  : 'a document -> 'a
 
-val length : 'a t -> int
-(** Length of a stack. *)
+(** Add a sentence on the top (with no state_id) *)
+val push : 'a document -> 'a -> unit
 
-val pop  : 'a t -> 'a
-(** Remove and returns the first element of the stack.
-    @raise Empty if empty. *)
+(** Remove the tip setence.  @raise Empty *)
+val pop : 'a document -> 'a
 
-val tip  : 'a t -> 'a
-(** Remove the first element of the stack without modifying it.
-    @raise Empty if empty. *)
+(** Assign the state_id of the tip.  @raise Empty *)
+val assign_tip_id : 'a document -> id -> unit
 
-val to_list : 'a t -> 'a list
-(** Convert to a list. *)
+(** [cut_at d id] cuts the document at [id] that is the new tip.
+    Returns the list of sentences that were cut.
+    @raise Not_found *)
+val cut_at : 'a document -> id -> 'a list
 
-val find_map : ('a -> bool -> 'b option) -> 'a t -> 'b
-(** Find the first element that returns [Some _].
-    The boolean tells If the element is inside the focused zone.
-    @raise Not_found it there is none. *)
+(* Functions that work on the whole document ********************************* *)
 
-type ('b, 'c) seek = ('b, 'c) CSig.seek = Stop of 'b | Next of 'c
+(** returns the id of the topmost sentence validating the predicate and
+    a boolean that is true if one needs to unfocus the document to access
+    such sentence.  @raise Not_found *)
+val find_id : 'a document -> (id -> 'a -> bool) -> id * bool
 
-(** [seek f acc s] acts like [List.fold_left f acc s] while [f] returns
-    [Next acc']; it stops returning [b] as soon as [f] returns [Stop b].
-    The stack is traversed from the top and is not altered.
-    @raise Not_found it there is none. *)
-val fold_until : ('c -> 'a -> ('b, 'c) seek) -> 'c -> 'a t -> 'b
+(** look for a sentence validating the predicate.  The boolean is true
+    if the sentence is in the zone currently focused.  @raise Not_found *)
+val find : 'a document -> (bool -> id option -> 'a -> bool) -> 'a
+val find_map : 'a document -> (bool -> id option -> 'a -> 'b option) -> 'b
 
 (** After [focus s c1 c2] the top of [s] is the topmost element [x] such that
     [c1 x] is [true] and the bottom is the first element [y] following [x]
-    such that [c2 y] is [true].  After a focus push/pop/top/fold_until
-    only use the focused part.
-    @raise Invalid_argument "CStack.focus" if there is no such [x] and [y] *)
-val focus : 'a t -> cond_top:('a -> bool) -> cond_bot:('a -> bool) -> unit
+    such that [c2 y] is [true].
+    @raise Invalid_argument if there is no such [x] and [y] or already focused *)
+val focus :
+  'a document ->
+    cond_top:(id -> 'a -> bool) -> cond_bot:(id -> 'a -> bool) -> unit
 
 (** Undoes a [focus].
     @raise Invalid_argument "CStack.unfocus" if the stack is not focused *)
-val unfocus : 'a t -> unit
+val unfocus : 'a document -> unit
+
+(** Is the document focused *)
+val focused : 'a document -> bool
+
+(** No sentences at all *)
+val is_empty : 'a document -> bool
+
+(** returns the 1 to-last sentence, and true if we need to unfocus to reach it.
+    @raise Not_found *)
+val before_tip : 'a document -> id * bool
+
+(** Is the id in the focused zone? *)
+val is_in_focus : 'a document -> id -> bool
+
+(** Folds over the whole document starting from the topmost (maybe unfocused)
+    sentence. *)
+val fold_all :
+  'a document -> 'c -> ('c -> bool -> id option -> 'a -> 'c) -> 'c
 
-(** Is the stack focused *)
-val focused : 'a t -> bool
+(** Returns (top,bot) such that the document is morally (top @ s @ bot) where
+    s is the focused part.  @raise Invalid_argument *)
+val context : 'a document -> (id * 'a) list * (id * 'a) list
 
-(** Returns [top, s, bot] where [top @ s @ bot] is the full stack, and [s]
-    the focused part *)
-val to_lists : 'a t -> 'a list * 'a list * 'a list
+(** debug print *)
+val print :
+  'a document -> (bool -> id option -> 'a ->  Pp.std_ppcmds) -> Pp.std_ppcmds