just replace the necessary part of the page

/*  A simple, one-room, scalable real-time web chat, with file sharing

    Copyright © 2012 Frederic Ye
    Copyright © 2010-2011 MLstate

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as
    published by the Free Software Foundation, either version 3 of the
    License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

import stdlib.system

/** Constants **/

GITHUB_USER = "Aqua-Ye"
GITHUB_REPO = "OpaChat"
NB_LAST_MSGS = 10

/** Types **/

type user = { int id, string name }
type source = { system } or { user user }
type message = {
  source source,
  string text,
  Date.date date,
}
type media = {
  source source,
  string name,
  string src,
  string mimetype,
  Date.date date,
}
type client_channel = channel(void)
type network_msg =
   {message message}
or {media media}
or {(user, client_channel) connection}
or {user disconnection}
or {stats}

/** Database **/

database intmap(message) /history

exposed Network.network(network_msg) room = Network.cloud("room")
private reference(intmap(user)) users = ServerReference.create(IntMap.empty)
private launch_date = Date.now()

/** Page **/

watch_button =

fork_button =

function build_page(content) {

OpaChat

      {watch_button}
      {fork_button}

{content}

}

/** Connection **/

server function server_observe(message) {
  match (message) {
  case {connection:(user, client_channel)} :
    ServerReference.update(users, IntMap.add(user.id, user, _))
    Network.broadcast({stats}, room)
    Session.on_remove(client_channel, function() {
      server_observe({disconnection:user})
    })
  case {disconnection:user} :
    ServerReference.update(users, IntMap.remove(user.id, _))
    Network.broadcast({stats}, room)
  default: void
  }
}

_ = Network.observe(server_observe, room)

/** Stats **/

server function mem() {
  System.get_memory_usage()/(1024*1024)
}

server function compute_stats() {
  uptime_duration = Date.between(launch_date, Date.now())
  uptime = Date.of_duration(uptime_duration)
  uptime = Date.shift_backward(uptime, Date.to_duration(Date.milliseconds(3600000))) // 1 hour shift
  (uptime, mem())
}

client @async function update_stats((uptime, mem)) {
  #uptime = <>Uptime: {Date.to_string_time_only(uptime)}</>
  #memory = <>Memory: {mem} Mo</>
}

/** Users **/

client @async function update_users(nb_users, users) {
  #users = <>Users: {nb_users}</>
  #user_list =
{users}

}

/** Conversation **/

function source_to_html(source) {
  match (source) {
  case {system} :
  case {~user} : {user.name}
  }
}

client @async function message_update(stats, list(message) messages) {
  update_stats(stats)
  List.iter(function(message) {
    date = Date.to_formatted_string(Date.default_printer, message.date)
    time = Date.to_string_time_only(message.date)
    line =

              {time}
              { source_to_html(message.source) }
              {message.text}

    #conversation =+ line
  }, messages)
  Dom.scroll_to_bottom(#conversation)
}

client @async function media_update(stats, list(media) medias) {
  update_stats(stats)
  List.iter(function(media) {
    date = Date.to_formatted_string(Date.default_printer, media.date)
    time = Date.to_string_time_only(media.date)
    media_parser = parser {
      case "image/" .*: {image}
      case "audio/" .*: {audio}
      case "video/" .*: {video}
    }
    line =

              {time}
              { source_to_html(media.source) }
              { match (Parser.try_parse(media_parser, media.mimetype)) {
                case {some:{image}}:

                case {some:{audio}}:
                  <audio src="{media.src}"
                         controls="controls"
                         type="{media.mimetype}"
                         preload="auto">
                    Your browser does not support the audio tag!
                  </audio>
                case {some:{video}}:
                  <video src="{media.src}"
                         controls="controls"
                         preload="auto"
                         type="{media.name}">
                    Your browser does not support the video tag!
                  </video>
                default:
                   is sharing a file :
                    {media.name}

                } }

    #conversation =+ line
  }, medias)
  Dom.scroll_to_bottom(#conversation)
}

exposed @async function broadcast(user, text) {
  message = {source:user, ~text, date:Date.now()}
  /history[?] <- message
  Network.broadcast({~message}, room)
}

client @async function send_message(user, _) {
  broadcast(user, Dom.get_value(#entry))
  Dom.clear_value(#entry)
}

server function file_uploaded(user)(name, mimetype, key) {
  media = {
    source: {~user},
    ~name,
    src: "/file/{key}",
    ~mimetype,
    date: Date.now(),
  }
  Network.broadcast({~media}, room)
}

server function client_observe(msg) {
  match (msg) {
  case {~message} :
    message_update(compute_stats(), [message])
  case {~media} :
    media_update(compute_stats(), [media])
  case {connection:(user, _)} :
    message = {
      source: {system},
      text : "{user.name} joined the room",
      date : Date.now(),
    }
    message_update(compute_stats(), [message])
  case {disconnection:user} :
    message = {
      source: {system},
      text : "{user.name} left the room",
      date : Date.now(),
    }
    message_update(compute_stats(), [message])
  case {stats} :
    update_stats(compute_stats())
    users = ServerReference.get(users)
            |> IntMap.To.val_list(_)
            |> List.sort_by(function(u){u.name}, _)
    users_html_list =
      List.fold(function(user, acc) {

{user.name}

        <+> acc
      }, users, <></>)
    update_users(List.length(users), users_html_list)
  default : void
  }
}

// Init the client from the server
server function init_client(user, client_channel, _) {
  // Observe client
  obs = Network.observe(client_observe, room)
  Network.broadcast({connection:(user, client_channel)}, room)
  // Observe disconnection
  Dom.bind_beforeunload_confirmation(function(_) {
    Network.broadcast({disconnection:user}, room)
    Network.unobserve(obs)
    none
  })
  // Send NB_LAST_MSGS messages
  history_list = IntMap.To.val_list(/history)
  len = List.length(history_list)
  history = List.drop(len-NB_LAST_MSGS, history_list)
  message_update(compute_stats(), history)
  // Initialize OpaShare
  OpaShare.init(file_uploaded(user))
}

server @async function enter_chat(user_name, client_channel) {
  user = {
    id: Random.int(max_int),
    name: user_name
  }
  // #Body is the default body id in Opa
  #main =

Users online

      {OpaShare.html()}

        <input id=#entry
               autofocus="autofocus"
               onready={function(_){Dom.give_focus(#entry)}}
               onnewline={send_message({~user}, _)}
               x-webkit-speech="x-webkit-speech"/>

}

client @async function join(_) {
  name = Dom.get_value(#name)
  client_channel = Session.make_callback(ignore)
  enter_chat(name, client_channel)
}

// Page headers
headers =
  Xhtml.of_string_unsafe("
") <+>
  <meta charset="utf-8"></meta>
  <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"></meta>
  <meta name="viewport" content="width=device-width,initial-scale=1"></meta>

// Start page
server function start() {
  page = build_page(

A real-time web chat built in Opa.

      <input id=#name
             placeholder="Name"
             autofocus="autofocus"
             onready={function(_){Dom.give_focus(#name)}}
             onnewline={join}/>
       <button class="btn primary"
               onclick={join}>Join</button>

  )
  Resource.full_page_with_doctype(
    "OpaChat - a real-time web chat built in Opa",
    {html5},
    page, headers, {success},
    []
  )
}

// Parse URL
url_parser = parser {
  case "/file/" key=Rule.integer:
    match (OpaShare.get(key)) {
    case {some:file}:
      Resource.binary(file.content, file.mimetype)
      |> Resource.add_header(_, {content_disposition:{attachment:file.name}})
    default: start()
    }
  case (.*): start()
}

// Start the server
Server.start(Server.http, [
  { resources : @static_resource_directory("resources") }, // include resources directory
  { register : [
      "/resources/css/bootstrap.min.css",
      "/resources/css/bootstrap-responsive.min.css",
      "/resources/css/style.css",
    ] }, // include CSS in headers
  { custom : url_parser } // URL parser
])

/*  A simple, one-room, scalable real-time web chat, with file sharing

    Copyright © 2012 Frederic Ye
    Copyright © 2010-2011 MLstate

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as
    published by the Free Software Foundation, either version 3 of the
    License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

import stdlib.system

/** Constants **/

GITHUB_USER = "Aqua-Ye"
GITHUB_REPO = "OpaChat"
NB_LAST_MSGS = 10

/** Types **/

type user = { int id, string name }
type source = { system } or { user user }
type message = {
  source source,
  string text,
  Date.date date,
}
type media = {
  source source,
  string name,
  string src,
  string mimetype,
  Date.date date,
}
type client_channel = channel(void)
type network_msg =
   {message message}
or {media media}
or {(user, client_channel) connection}
or {user disconnection}
or {stats}

/** Database **/

database intmap(message) /history

exposed Network.network(network_msg) room = Network.cloud("room")
private reference(intmap(user)) users = ServerReference.create(IntMap.empty)
private launch_date = Date.now()

/** Page **/

watch_button =

fork_button =

function build_page(content) {

OpaChat

      {watch_button}
      {fork_button}

{content}

}

/** Connection **/

server function server_observe(message) {
  match (message) {
  case {connection:(user, client_channel)} :
    ServerReference.update(users, IntMap.add(user.id, user, _))
    Network.broadcast({stats}, room)
    Session.on_remove(client_channel, function() {
      server_observe({disconnection:user})
    })
  case {disconnection:user} :
    ServerReference.update(users, IntMap.remove(user.id, _))
    Network.broadcast({stats}, room)
  default: void
  }
}

_ = Network.observe(server_observe, room)

/** Stats **/

server function mem() {
  System.get_memory_usage()/(1024*1024)
}

server function compute_stats() {
  uptime_duration = Date.between(launch_date, Date.now())
  uptime = Date.of_duration(uptime_duration)
  uptime = Date.shift_backward(uptime, Date.to_duration(Date.milliseconds(3600000))) // 1 hour shift
  (uptime, mem())
}

client @async function update_stats((uptime, mem)) {
  #uptime = <>Uptime: {Date.to_string_time_only(uptime)}</>
  #memory = <>Memory: {mem} Mo</>
}

/** Users **/

client @async function update_users(nb_users, users) {
  #users = <>Users: {nb_users}</>
  #user_list =
{users}

}

/** Conversation **/

function source_to_html(source) {
  match (source) {
  case {system} :
  case {~user} : {user.name}
  }
}

client @async function message_update(stats, list(message) messages) {
  update_stats(stats)
  List.iter(function(message) {
    date = Date.to_formatted_string(Date.default_printer, message.date)
    time = Date.to_string_time_only(message.date)
    line =

              {time}
              { source_to_html(message.source) }
              {message.text}

    #conversation =+ line
  }, messages)
  Dom.scroll_to_bottom(#conversation)
}

client @async function media_update(stats, list(media) medias) {
  update_stats(stats)
  List.iter(function(media) {
    date = Date.to_formatted_string(Date.default_printer, media.date)
    time = Date.to_string_time_only(media.date)
    media_parser = parser {
      case "image/" .*: {image}
      case "audio/" .*: {audio}
      case "video/" .*: {video}
    }
    line =

              {time}
              { source_to_html(media.source) }
              { match (Parser.try_parse(media_parser, media.mimetype)) {
                case {some:{image}}:

                case {some:{audio}}:
                  <audio src="{media.src}"
                         controls="controls"
                         type="{media.mimetype}"
                         preload="auto">
                    Your browser does not support the audio tag!
                  </audio>
                case {some:{video}}:
                  <video src="{media.src}"
                         controls="controls"
                         preload="auto"
                         type="{media.name}">
                    Your browser does not support the video tag!
                  </video>
                default:
                   is sharing a file :
                    {media.name}

                } }

    #conversation =+ line
  }, medias)
  Dom.scroll_to_bottom(#conversation)
}

exposed @async function broadcast(user, text) {
  message = {source:user, ~text, date:Date.now()}
  /history[?] <- message
  Network.broadcast({~message}, room)
}

client @async function send_message(user, _) {
  broadcast(user, Dom.get_value(#entry))
  Dom.clear_value(#entry)
}

server function file_uploaded(user)(name, mimetype, key) {
  media = {
    source: {~user},
    ~name,
    src: "/file/{key}",
    ~mimetype,
    date: Date.now(),
  }
  Network.broadcast({~media}, room)
}

server function client_observe(msg) {
  match (msg) {
  case {~message} :
    message_update(compute_stats(), [message])
  case {~media} :
    media_update(compute_stats(), [media])
  case {connection:(user, _)} :
    message = {
      source: {system},
      text : "{user.name} joined the room",
      date : Date.now(),
    }
    message_update(compute_stats(), [message])
  case {disconnection:user} :
    message = {
      source: {system},
      text : "{user.name} left the room",
      date : Date.now(),
    }
    message_update(compute_stats(), [message])
  case {stats} :
    update_stats(compute_stats())
    users = ServerReference.get(users)
            |> IntMap.To.val_list(_)
            |> List.sort_by(function(u){u.name}, _)
    users_html_list =
      List.fold(function(user, acc) {

{user.name}

        <+> acc
      }, users, <></>)
    update_users(List.length(users), users_html_list)
  default : void
  }
}

// Init the client from the server
server function init_client(user, client_channel, _) {
  // Observe client
  obs = Network.observe(client_observe, room)
  Network.broadcast({connection:(user, client_channel)}, room)
  // Observe disconnection
  Dom.bind_beforeunload_confirmation(function(_) {
    Network.broadcast({disconnection:user}, room)
    Network.unobserve(obs)
    none
  })
  // Send NB_LAST_MSGS messages
  history_list = IntMap.To.val_list(/history)
  len = List.length(history_list)
  history = List.drop(len-NB_LAST_MSGS, history_list)
  message_update(compute_stats(), history)
  // Initialize OpaShare
  OpaShare.init(file_uploaded(user))
}

server @async function enter_chat(user_name, client_channel) {
  user = {
    id: Random.int(max_int),
    name: user_name
  }
  // #Body is the default body id in Opa
  #Body = build_page(

Users online

      {OpaShare.html()}

        <input id=#entry
               autofocus="autofocus"
               onready={function(_){Dom.give_focus(#entry)}}
               onnewline={send_message({~user}, _)}
               x-webkit-speech="x-webkit-speech"/>

  )
}

client @async function join(_) {
  name = Dom.get_value(#name)
  client_channel = Session.make_callback(ignore)
  enter_chat(name, client_channel)
}

// Page headers
headers =
  Xhtml.of_string_unsafe("
") <+>
  <meta charset="utf-8"></meta>
  <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"></meta>
  <meta name="viewport" content="width=device-width,initial-scale=1"></meta>

// Start page
server function start() {
  page = build_page(

A real-time web chat built in Opa.

      <input id=#name
             placeholder="Name"
             autofocus="autofocus"
             onready={function(_){Dom.give_focus(#name)}}
             onnewline={join}/>
       <button class="btn primary"
               onclick={join}>Join</button>

  )
  Resource.full_page_with_doctype(
    "OpaChat - a real-time web chat built in Opa",
    {html5},
    page, headers, {success},
    []
  )
}

// Parse URL
url_parser = parser {
  case "/file/" key=Rule.integer:
    match (OpaShare.get(key)) {
    case {some:file}:
      Resource.binary(file.content, file.mimetype)
      |> Resource.add_header(_, {content_disposition:{attachment:file.name}})
    default: start()
    }
  case (.*): start()
}

// Start the server
Server.start(Server.http, [
  { resources : @static_resource_directory("resources") }, // include resources directory
  { register : [
      "/resources/css/bootstrap.min.css",
      "/resources/css/bootstrap-responsive.min.css",
      "/resources/css/style.css",
    ] }, // include CSS in headers
  { custom : url_parser } // URL parser
])


function to change the mode

function to change the mode

type Modeler.objects = { cube: (float, float, float); id: hidden_id } ;

type Modeler.scene = list(Modeler.objects) ;

type Modeler.tool.mode = {selection} / {add_cube} ;

type Modeler.modeler = {
  address: string;
  scene: Modeler.scene;
  mode: Modeler.tool.mode
} ;

Scene = {{
  empty() = [ {cube=(0.0, 0.0, -3.0); id=CHF()}, {cube=(3.0, 0.0, 0.0); id=CHF()}, {cube=(6.0, 0.0, 0.0); id=CHF()} ] ;

  add_cube(scene, where) = List.cons({cube=(where.x, 0.0, where.z); id=CHF()}, scene) ;

}} ;

Modeler = {{
  empty(scene_url) = { address=scene_url; scene=Scene.empty(); mode={selection} } ;

  use_tool(modeler, where, possible_target) =
    do Log.info("Modeler", "using tool at ({where.x},{where.z}) perhaps on the target: '{possible_target}'");
    match modeler.mode with
    | {add_cube} -> { modeler with scene=Scene.add_cube(modeler.scene, where) }
    | {selection} -> modeler
    end ;

  change_tool(modeler, new_mode) = { modeler with mode=new_mode };

}} ;

@client GuiModeler = {{

  @private on_message(state : Modeler.modeler, message) = match message with
    | {click_on_scene; ~where; ~possible_target} -> { set=Modeler.use_tool(state, where, possible_target) }
    //| _ -> {unchanged}
    end ;

  init(scene_url, canvas_sel, width, height) : outcome =
    (channel, get_scene) =
      (channel, get_state) = SessionExt.make_with_getter(Modeler.empty(scene_url), on_message);
      (channel, (-> get_state().scene)) ;
    mouse_listener(e) = match e with
      | { mousedown; ~x; ~z; ~possible_target } -> Session.send(channel, {click_on_scene; where={~x; ~z}; ~possible_target})
      end ;
    res = initGL(canvas_sel, width, height, get_scene, mouse_listener) ;
    match res with
    | {success} ->

      res
    | _ -> res
    end ;

}}

type Modeler.objects = { cube: (float, float, float); id: hidden_id } ;

type Modeler.scene = list(Modeler.objects) ;

type Modeler.tool.mode = {selection} / {add_cube} ;

type Modeler.modeler = {
  address: string;
  scene: Modeler.scene;
  mode: Modeler.tool.mode
} ;

Scene = {{
  empty() = [ {cube=(0.0, 0.0, -3.0); id=CHF()}, {cube=(3.0, 0.0, 0.0); id=CHF()}, {cube=(6.0, 0.0, 0.0); id=CHF()} ] ;

  add_cube(scene, where) = List.cons({cube=(where.x, 0.0, where.z); id=CHF()}, scene) ;

}} ;

Modeler = {{
  empty(scene_url) = { address=scene_url; scene=Scene.empty(); mode={selection} } ;

  use_tool(modeler, where, possible_target) =
    do Log.info("Modeler", "using tool at ({where.x},{where.z}) perhaps on the target: '{possible_target}'");
    match modeler.mode with
    | {add_cube} -> { modeler with scene=Scene.add_cube(modeler.scene, where) }
    | {selection} -> modeler
    end ;

}} ;

@client GuiModeler = {{

  @private on_message(state : Modeler.modeler, message) = match message with
    | {click_on_scene; ~where; ~possible_target} -> { set=Modeler.use_tool(state, where, possible_target) }
    //| _ -> {unchanged}
    end ;

  init(scene_url, canvas_sel, width, height) : outcome =
    (channel, get_scene) =
      (channel, get_state) = SessionExt.make_with_getter(Modeler.empty(scene_url), on_message);
      (channel, (-> get_state().scene)) ;
    mouse_listener(e) = match e with
      | { mousedown; ~x; ~z; ~possible_target } -> Session.send(channel, {click_on_scene; where={~x; ~z}; ~possible_target})
      end ;
    res = initGL(canvas_sel, width, height, get_scene, mouse_listener) ;
    match res with
    | {success} ->

      res
    | _ -> res
    end ;

}}


quick change to test the scene getter

quick change to test the scene getter

@private type my_custom_shaderProgram = {
  program: Webgl.WebGLProgram;
  vertexPositionAttribute: Webgl.GLint;
  vertexNormalAttribute: Webgl.GLint;
  pMatrixUniform: Webgl.WebGLUniformLocation;
  mvMatrixUniform: Webgl.WebGLUniformLocation;
  nMatrixUniform: Webgl.WebGLUniformLocation;
  ambientColorUniform: Webgl.WebGLUniformLocation;
  lightingDirectionUniform: Webgl.WebGLUniformLocation;
  useLightingUniform: Webgl.WebGLUniformLocation
};

@private type static_buffer = {
  positions: Webgl.WebGLBuffer;
  itemSize: int; numItems: int;
  normals: Webgl.WebGLBuffer
};

@private type engine = {
  context: Webgl.Context.private;
  canvas: { selector:dom; width: int; height: int };
  shaderProgram: my_custom_shaderProgram
  static_buffers: { repcoords: { x:static_buffer; y:static_buffer; z:static_buffer } }
} ;

initShaders(gl) =
  f(e, str) =
    shader = Webgl.createShader(gl, e);
    do Webgl.shaderSource(gl, shader, str);
    do Webgl.compileShader(gl, shader);
    shader;
  fragmentShader = f(Webgl.FRAGMENT_SHADER(gl), CustomShaders.shader_fs);
  vertexShader = f(Webgl.VERTEX_SHADER(gl), CustomShaders.shader_vs);
  // TODO getShaderParameter
  shaderProgram = Webgl.createProgram(gl);
  do Webgl.attachShader(gl, shaderProgram, vertexShader);
  do Webgl.attachShader(gl, shaderProgram, fragmentShader);
  do Webgl.linkProgram(gl, shaderProgram);
  // TODO : getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
  do Webgl.useProgram(gl, shaderProgram);
  shaderProgram =
    vertexPositionAttribute = Webgl.getAttribLocation(gl, shaderProgram, "aVertexPosition");
    vertexNormalAttribute = Webgl.getAttribLocation(gl, shaderProgram, "aVertexNormal");
    do Webgl.enableVertexAttribArray(gl, vertexPositionAttribute);
    do Webgl.enableVertexAttribArray(gl, vertexNormalAttribute);
    { program = shaderProgram;
      ~vertexPositionAttribute;
      ~vertexNormalAttribute;
      pMatrixUniform = Webgl.getUniformLocation(gl, shaderProgram, "uPMatrix");
      mvMatrixUniform = Webgl.getUniformLocation(gl, shaderProgram, "uMVMatrix");
      nMatrixUniform = Webgl.getUniformLocation(gl, shaderProgram, "uNMatrix");
      ambientColorUniform = Webgl.getUniformLocation(gl, shaderProgram, "uAmbientColor");
      lightingDirectionUniform = Webgl.getUniformLocation(gl, shaderProgram, "uLightingDirection");
      useLightingUniform = Webgl.getUniformLocation(gl, shaderProgram, "uUseLighting");
    };
  shaderProgram
;

initBuffers(gl) =
  //global variable to hold the square buffer
  //We create a buffer for the square's vertex positions.
  squareVertexPositionBuffer = Webgl.createBuffer(gl);
  //tells WebGL that any following operations that act on buffers should use the one we specify
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), squareVertexPositionBuffer);
  //define our vertex positions as a list
  vertices = [
      // Front face
      -1.0, -1.0,  1.0,
       1.0, -1.0,  1.0,
       1.0,  1.0,  1.0,
      -1.0,  1.0,  1.0,

      // Back face
      -1.0, -1.0, -1.0,
      -1.0,  1.0, -1.0,
       1.0,  1.0, -1.0,
       1.0, -1.0, -1.0,

      // Top face
      -1.0,  1.0, -1.0,
      -1.0,  1.0,  1.0,
       1.0,  1.0,  1.0,
       1.0,  1.0, -1.0,

      // Bottom face
      -1.0, -1.0, -1.0,
       1.0, -1.0, -1.0,
       1.0, -1.0,  1.0,
      -1.0, -1.0,  1.0,

      // Right face
       1.0, -1.0, -1.0,
       1.0,  1.0, -1.0,
       1.0,  1.0,  1.0,
       1.0, -1.0,  1.0,

      // Left face
      -1.0, -1.0, -1.0,
      -1.0, -1.0,  1.0,
      -1.0,  1.0,  1.0,
      -1.0,  1.0, -1.0,
    ];
  vertexNormals = [
    // Front
     0.0,  0.0,  1.0,
     0.0,  0.0,  1.0,
     0.0,  0.0,  1.0,
     0.0,  0.0,  1.0,

    // Back
     0.0,  0.0, -1.0,
     0.0,  0.0, -1.0,
     0.0,  0.0, -1.0,
     0.0,  0.0, -1.0,

    // Top
     0.0,  1.0,  0.0,
     0.0,  1.0,  0.0,
     0.0,  1.0,  0.0,
     0.0,  1.0,  0.0,

    // Bottom
     0.0, -1.0,  0.0,
     0.0, -1.0,  0.0,
     0.0, -1.0,  0.0,
     0.0, -1.0,  0.0,

    // Right
     1.0,  0.0,  0.0,
     1.0,  0.0,  0.0,
     1.0,  0.0,  0.0,
     1.0,  0.0,  0.0,

    // Left
    -1.0,  0.0,  0.0,
    -1.0,  0.0,  0.0,
    -1.0,  0.0,  0.0,
    -1.0,  0.0,  0.0
  ];
  cubeVertexIndices = [
            0, 1, 2,      0, 2, 3,    // Front face
            4, 5, 6,      4, 6, 7,    // Back face
            8, 9, 10,     8, 10, 11,  // Top face
            12, 13, 14,   12, 14, 15, // Bottom face
            16, 17, 18,   16, 18, 19, // Right face
            20, 21, 22,   20, 22, 23  // Left face
        ];
  //Now, we create a Float32Array object based on our list,
  //and tell WebGL to use it to fill the current buffer
  do Webgl.bufferData(gl, Webgl.ARRAY_BUFFER(gl), Webgl.Float32Array.to_ArrayBuffer(Webgl.Float32Array.from_float_list(vertices)), Webgl.STATIC_DRAW(gl));
  //this 9-element buffer actually represents three separate vertex
  //positions (numItems), each of which is made up of three numbers (itemSize).
  //do Webgl.set_itemSize(squareVertexPositionBuffer, 3);
  //do Webgl.set_numItems(squareVertexPositionBuffer, 4);
  squareVertexNormalBuffer = Webgl.createBuffer(gl);
  //tells WebGL that any following operations that act on buffers should use the one we specify
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), squareVertexNormalBuffer);
  do Webgl.bufferData(gl, Webgl.ARRAY_BUFFER(gl), Webgl.Float32Array.to_ArrayBuffer(Webgl.Float32Array.from_float_list(vertexNormals)), Webgl.STATIC_DRAW(gl));
  cubeVertexIndexBuffer = Webgl.createBuffer(gl);
  do Webgl.bindBuffer(gl, Webgl.ELEMENT_ARRAY_BUFFER(gl), cubeVertexIndexBuffer);
  do Webgl.bufferData(gl, Webgl.ELEMENT_ARRAY_BUFFER(gl), Webgl.Uint16Array.to_ArrayBuffer(Webgl.Uint16Array.from_int_list(cubeVertexIndices)), Webgl.STATIC_DRAW(gl));
  { positions=squareVertexPositionBuffer; itemSize=3; numItems=24; normals=squareVertexNormalBuffer; indexs=cubeVertexIndexBuffer }
;

initLineXBuffers(gl, orient) =
  (vertices, vertexNormals) = match orient with
    | {x} -> ([ 0.0, 0.0, 0.0, 5.0, 0.0, 0.0 ], [ 2.5, 0.0, 0.0,        2.5, -1.0, 0.0 ])
    | {y} -> ([ 0.0, 0.0, 0.0, 0.0, 5.0, 0.0 ], [ 0.0, 2.5, 0.0,        -1.0, 2.5, 0.0 ])
    | {z} -> ([ 0.0, 0.0, 0.0, 0.0, 0.0, 5.0 ], [ 0.0, 0.0, 2.5,        0.0, -1.0, 2.5 ])
    end ;
  vertexPositionBuffer = Webgl.createBuffer(gl);
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), vertexPositionBuffer);
  do Webgl.bufferData(gl, Webgl.ARRAY_BUFFER(gl),
    Webgl.Float32Array.to_ArrayBuffer(Webgl.Float32Array.from_float_list(vertices)),
    Webgl.STATIC_DRAW(gl));
  vertexNormalBuffer = Webgl.createBuffer(gl);
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), vertexNormalBuffer);
  do Webgl.bufferData(gl, Webgl.ARRAY_BUFFER(gl),
    Webgl.Float32Array.to_ArrayBuffer(Webgl.Float32Array.from_float_list(vertexNormals)),
    Webgl.STATIC_DRAW(gl));
  { positions=vertexPositionBuffer; itemSize=3; numItems=2; normals=vertexNormalBuffer }
;

setMatrixUniforms(gl, shaderProgram, pMatrix, mvMatrix) =
  a =
    b = mat4.to_list(pMatrix);
    c = Webgl.Float32Array.from_float_list(b);
    c;
  e =
    f = mat4.to_list(mvMatrix);
    g = Webgl.Float32Array.from_float_list(f);
    g;
  do Webgl.uniformMatrix4fv(gl, shaderProgram.pMatrixUniform, false, a);
  do Webgl.uniformMatrix4fv(gl, shaderProgram.mvMatrixUniform, false, e);
  normalMatrix = mat3.create();
  do mat4.toInverseMat3(mvMatrix, normalMatrix);
  do mat3.transpose(normalMatrix, normalMatrix);
  do Webgl.uniformMatrix3fv(gl, shaderProgram.nMatrixUniform, false, Webgl.Float32Array.from_float_list(mat3.to_list(normalMatrix)));
  void
;

setup_boxes(eng) =
  sep_largeur = 2;
  g(x, y, w, h) = { ~x; ~y; ~w; ~h } ;
  compute_left_right(x) = if ((mod(x, 2)) == 0) then
      a = (x / 2) - 1;
      (a, a)
    else
      b = (x / 2);
      (b - 1, b);
  (w_l, w_r) = compute_left_right(eng.canvas.width);
  (h_u, h_d) = compute_left_right(eng.canvas.height);
  { _YX=g(0, h_d+sep_largeur, w_l, h_u); _YZ=g(w_l+sep_largeur, h_d+sep_largeur, w_r, h_u);
    _ZX=g(0, 0, w_l, h_d); _3D=g(w_l+sep_largeur, 0, w_r, h_d) }
;

drawScene_for_a_viewport(eng, viewport, eye, up, scene, squareVertexPositionBuffer) =
  gl = eng.context; shaderProgram = eng.shaderProgram; repcoords = eng.static_buffers.repcoords;
  do Webgl.viewport(gl, viewport.x, viewport.y, viewport.w, viewport.h);
  pMatrix =
    tmp_pMatrix = mat4.create();
    do mat4.perspective(45., float_of_int(eng.canvas.width) / float_of_int(eng.canvas.height), 0.1, 100.0, tmp_pMatrix);
    c = mat4.create() ;
    do mat4.lookAt(vec3.from_public(eye), vec3.from_public((0.0, 0.0, 0.0)), vec3.from_public(up), c);
    do mat4.multiply(tmp_pMatrix, c, tmp_pMatrix);
    tmp_pMatrix;
  mvMatrix =
    tmp_mvMatrix = mat4.create();
    do mat4.identity(tmp_mvMatrix);
    tmp_mvMatrix;
  do setMatrixUniforms(gl, shaderProgram, pMatrix, mvMatrix);
  draw_rep(r, g, b, rep) =
    do Webgl.uniform1i(gl, shaderProgram.useLightingUniform, 0); // 0 = false
    do Webgl.uniform3f(gl, shaderProgram.ambientColorUniform, r, g, b);
    do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), rep.positions);
    do Webgl.vertexAttribPointer(gl, shaderProgram.vertexPositionAttribute, rep.itemSize, Webgl.FLOAT(gl), false, 0, 0);
    do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), rep.normals);
    do Webgl.vertexAttribPointer(gl, shaderProgram.vertexNormalAttribute, rep.itemSize, Webgl.FLOAT(gl), false, 0, 0);
    do Webgl.drawArrays(gl, Webgl.LINES(gl), 0, rep.numItems);
    void ;
  do draw_rep(1.0, 0.0, 0.0, repcoords.x);
  do draw_rep(0.0, 1.0, 0.0, repcoords.y);
  do draw_rep(0.0, 0.0, 1.0, repcoords.z);

  do Webgl.uniform1i(gl, shaderProgram.useLightingUniform, 1); // 1 = true
  do Webgl.uniform3f(gl, shaderProgram.ambientColorUniform, 0.4, 0.4, 0.4);
  do Webgl.uniform3f(gl, shaderProgram.lightingDirectionUniform, 0.85, 0.8, 0.75);
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), squareVertexPositionBuffer.positions);
  do Webgl.vertexAttribPointer(gl, shaderProgram.vertexPositionAttribute, squareVertexPositionBuffer.itemSize, Webgl.FLOAT(gl), false, 0, 0);
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), squareVertexPositionBuffer.normals);
  do Webgl.vertexAttribPointer(gl, shaderProgram.vertexNormalAttribute, squareVertexPositionBuffer.itemSize, Webgl.FLOAT(gl), false, 0, 0);
  do Webgl.bindBuffer(gl, Webgl.ELEMENT_ARRAY_BUFFER(gl), squareVertexPositionBuffer.indexs);

  do mat4.translate(mvMatrix, vec3.from_public(scene), mvMatrix);
  do setMatrixUniforms(gl, shaderProgram, pMatrix, mvMatrix);
  do Webgl.drawElements(gl, Webgl.TRIANGLES(gl), 36, Webgl.UNSIGNED_SHORT(gl), 0);

  void
;

drawScene_and_register(eng, get_scene : (->vec3), squareVertexPositionBuffer) =
  viewbox = setup_boxes(eng) ;
  rec aux(eng, squareVertexPositionBuffer) =
    gl = eng.context;
    scene = get_scene() ;
    do Webgl.clear(gl, Webgl.GLbitfield_OR(Webgl.COLOR_BUFFER_BIT(gl), Webgl.DEPTH_BUFFER_BIT(gl)));
    do drawScene_for_a_viewport(eng, viewbox._YX, (0.0, 0.0, 15.0), (0.0, 1.0, 0.0), scene, squareVertexPositionBuffer);
    do drawScene_for_a_viewport(eng, viewbox._YZ, (-15.0, 0.0, 0.0), (0.0, 1.0, 0.0), scene, squareVertexPositionBuffer);
    do drawScene_for_a_viewport(eng, viewbox._ZX, (0.0, -15.0, 0.0), (0.0, 0.0, 1.0), scene, squareVertexPositionBuffer);
    do drawScene_for_a_viewport(eng, viewbox._3D, (10.0, 5.0, 15.0), (0.0, 1.0, 0.0), scene, squareVertexPositionBuffer);
    do RequestAnimationFrame.request((_ -> aux(eng, squareVertexPositionBuffer)), #{id_canvas_area});
    void
    ;
  aux(eng, squareVertexPositionBuffer)
;

initGL(canvas_sel, width, height) : void =
  match Webgl.getContext(Dom.of_selection(canvas_sel), "experimental-webgl") with
  | { some=context } ->
    gl = context;
    eng : engine =
      start = @openrecord({ context=gl; canvas={ selector=canvas_sel; ~width; ~height } });
      start = { start with shaderProgram=initShaders(gl) };
      { start with static_buffers.repcoords=
        { x=initLineXBuffers(gl, {x}); y=initLineXBuffers(gl, {y}); z=initLineXBuffers(gl, {z}) } };
    squareVertexPositionBuffer = initBuffers(gl);
    //Clear screen and make everything light gray
    do Webgl.clearColor(gl, 0.9, 0.9, 0.9, 1.0);
    //we should do depth testing so that things drawn behind other
    //things should be hidden by the things in front of them).
    do Webgl.clearDepth(gl, 1.0);
    do Webgl.enable(gl, Webgl.DEPTH_TEST(gl));
    do Webgl.depthFunc(gl, Webgl.LEQUAL(gl));
    do drawScene_and_register(eng, (-> (0.0, -4.0, 0.0)), squareVertexPositionBuffer);
    void
  | { none } -> error("no context found")
  end ;

@private type my_custom_shaderProgram = {
  program: Webgl.WebGLProgram;
  vertexPositionAttribute: Webgl.GLint;
  vertexNormalAttribute: Webgl.GLint;
  pMatrixUniform: Webgl.WebGLUniformLocation;
  mvMatrixUniform: Webgl.WebGLUniformLocation;
  nMatrixUniform: Webgl.WebGLUniformLocation;
  ambientColorUniform: Webgl.WebGLUniformLocation;
  lightingDirectionUniform: Webgl.WebGLUniformLocation;
  useLightingUniform: Webgl.WebGLUniformLocation
};

@private type static_buffer = {
  positions: Webgl.WebGLBuffer;
  itemSize: int; numItems: int;
  normals: Webgl.WebGLBuffer
};

@private type engine = {
  context: Webgl.Context.private;
  canvas: { selector:dom; width: int; height: int };
  shaderProgram: my_custom_shaderProgram
  static_buffers: { repcoords: { x:static_buffer; y:static_buffer; z:static_buffer } }
} ;

initShaders(gl) =
  f(e, str) =
    shader = Webgl.createShader(gl, e);
    do Webgl.shaderSource(gl, shader, str);
    do Webgl.compileShader(gl, shader);
    shader;
  fragmentShader = f(Webgl.FRAGMENT_SHADER(gl), CustomShaders.shader_fs);
  vertexShader = f(Webgl.VERTEX_SHADER(gl), CustomShaders.shader_vs);
  // TODO getShaderParameter
  shaderProgram = Webgl.createProgram(gl);
  do Webgl.attachShader(gl, shaderProgram, vertexShader);
  do Webgl.attachShader(gl, shaderProgram, fragmentShader);
  do Webgl.linkProgram(gl, shaderProgram);
  // TODO : getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
  do Webgl.useProgram(gl, shaderProgram);
  shaderProgram =
    vertexPositionAttribute = Webgl.getAttribLocation(gl, shaderProgram, "aVertexPosition");
    vertexNormalAttribute = Webgl.getAttribLocation(gl, shaderProgram, "aVertexNormal");
    do Webgl.enableVertexAttribArray(gl, vertexPositionAttribute);
    do Webgl.enableVertexAttribArray(gl, vertexNormalAttribute);
    { program = shaderProgram;
      ~vertexPositionAttribute;
      ~vertexNormalAttribute;
      pMatrixUniform = Webgl.getUniformLocation(gl, shaderProgram, "uPMatrix");
      mvMatrixUniform = Webgl.getUniformLocation(gl, shaderProgram, "uMVMatrix");
      nMatrixUniform = Webgl.getUniformLocation(gl, shaderProgram, "uNMatrix");
      ambientColorUniform = Webgl.getUniformLocation(gl, shaderProgram, "uAmbientColor");
      lightingDirectionUniform = Webgl.getUniformLocation(gl, shaderProgram, "uLightingDirection");
      useLightingUniform = Webgl.getUniformLocation(gl, shaderProgram, "uUseLighting");
    };
  shaderProgram
;

initBuffers(gl) =
  //global variable to hold the square buffer
  //We create a buffer for the square's vertex positions.
  squareVertexPositionBuffer = Webgl.createBuffer(gl);
  //tells WebGL that any following operations that act on buffers should use the one we specify
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), squareVertexPositionBuffer);
  //define our vertex positions as a list
  vertices = [
      // Front face
      -1.0, -1.0,  1.0,
       1.0, -1.0,  1.0,
       1.0,  1.0,  1.0,
      -1.0,  1.0,  1.0,

      // Back face
      -1.0, -1.0, -1.0,
      -1.0,  1.0, -1.0,
       1.0,  1.0, -1.0,
       1.0, -1.0, -1.0,

      // Top face
      -1.0,  1.0, -1.0,
      -1.0,  1.0,  1.0,
       1.0,  1.0,  1.0,
       1.0,  1.0, -1.0,

      // Bottom face
      -1.0, -1.0, -1.0,
       1.0, -1.0, -1.0,
       1.0, -1.0,  1.0,
      -1.0, -1.0,  1.0,

      // Right face
       1.0, -1.0, -1.0,
       1.0,  1.0, -1.0,
       1.0,  1.0,  1.0,
       1.0, -1.0,  1.0,

      // Left face
      -1.0, -1.0, -1.0,
      -1.0, -1.0,  1.0,
      -1.0,  1.0,  1.0,
      -1.0,  1.0, -1.0,
    ];
  vertexNormals = [
    // Front
     0.0,  0.0,  1.0,
     0.0,  0.0,  1.0,
     0.0,  0.0,  1.0,
     0.0,  0.0,  1.0,

    // Back
     0.0,  0.0, -1.0,
     0.0,  0.0, -1.0,
     0.0,  0.0, -1.0,
     0.0,  0.0, -1.0,

    // Top
     0.0,  1.0,  0.0,
     0.0,  1.0,  0.0,
     0.0,  1.0,  0.0,
     0.0,  1.0,  0.0,

    // Bottom
     0.0, -1.0,  0.0,
     0.0, -1.0,  0.0,
     0.0, -1.0,  0.0,
     0.0, -1.0,  0.0,

    // Right
     1.0,  0.0,  0.0,
     1.0,  0.0,  0.0,
     1.0,  0.0,  0.0,
     1.0,  0.0,  0.0,

    // Left
    -1.0,  0.0,  0.0,
    -1.0,  0.0,  0.0,
    -1.0,  0.0,  0.0,
    -1.0,  0.0,  0.0
  ];
  cubeVertexIndices = [
            0, 1, 2,      0, 2, 3,    // Front face
            4, 5, 6,      4, 6, 7,    // Back face
            8, 9, 10,     8, 10, 11,  // Top face
            12, 13, 14,   12, 14, 15, // Bottom face
            16, 17, 18,   16, 18, 19, // Right face
            20, 21, 22,   20, 22, 23  // Left face
        ];
  //Now, we create a Float32Array object based on our list,
  //and tell WebGL to use it to fill the current buffer
  do Webgl.bufferData(gl, Webgl.ARRAY_BUFFER(gl), Webgl.Float32Array.to_ArrayBuffer(Webgl.Float32Array.from_float_list(vertices)), Webgl.STATIC_DRAW(gl));
  //this 9-element buffer actually represents three separate vertex
  //positions (numItems), each of which is made up of three numbers (itemSize).
  //do Webgl.set_itemSize(squareVertexPositionBuffer, 3);
  //do Webgl.set_numItems(squareVertexPositionBuffer, 4);
  squareVertexNormalBuffer = Webgl.createBuffer(gl);
  //tells WebGL that any following operations that act on buffers should use the one we specify
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), squareVertexNormalBuffer);
  do Webgl.bufferData(gl, Webgl.ARRAY_BUFFER(gl), Webgl.Float32Array.to_ArrayBuffer(Webgl.Float32Array.from_float_list(vertexNormals)), Webgl.STATIC_DRAW(gl));
  cubeVertexIndexBuffer = Webgl.createBuffer(gl);
  do Webgl.bindBuffer(gl, Webgl.ELEMENT_ARRAY_BUFFER(gl), cubeVertexIndexBuffer);
  do Webgl.bufferData(gl, Webgl.ELEMENT_ARRAY_BUFFER(gl), Webgl.Uint16Array.to_ArrayBuffer(Webgl.Uint16Array.from_int_list(cubeVertexIndices)), Webgl.STATIC_DRAW(gl));
  { positions=squareVertexPositionBuffer; itemSize=3; numItems=24; normals=squareVertexNormalBuffer; indexs=cubeVertexIndexBuffer }
;

initLineXBuffers(gl, orient) =
  (vertices, vertexNormals) = match orient with
    | {x} -> ([ 0.0, 0.0, 0.0, 5.0, 0.0, 0.0 ], [ 2.5, 0.0, 0.0,        2.5, -1.0, 0.0 ])
    | {y} -> ([ 0.0, 0.0, 0.0, 0.0, 5.0, 0.0 ], [ 0.0, 2.5, 0.0,        -1.0, 2.5, 0.0 ])
    | {z} -> ([ 0.0, 0.0, 0.0, 0.0, 0.0, 5.0 ], [ 0.0, 0.0, 2.5,        0.0, -1.0, 2.5 ])
    end ;
  vertexPositionBuffer = Webgl.createBuffer(gl);
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), vertexPositionBuffer);
  do Webgl.bufferData(gl, Webgl.ARRAY_BUFFER(gl),
    Webgl.Float32Array.to_ArrayBuffer(Webgl.Float32Array.from_float_list(vertices)),
    Webgl.STATIC_DRAW(gl));
  vertexNormalBuffer = Webgl.createBuffer(gl);
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), vertexNormalBuffer);
  do Webgl.bufferData(gl, Webgl.ARRAY_BUFFER(gl),
    Webgl.Float32Array.to_ArrayBuffer(Webgl.Float32Array.from_float_list(vertexNormals)),
    Webgl.STATIC_DRAW(gl));
  { positions=vertexPositionBuffer; itemSize=3; numItems=2; normals=vertexNormalBuffer }
;

setMatrixUniforms(gl, shaderProgram, pMatrix, mvMatrix) =
  a =
    b = mat4.to_list(pMatrix);
    c = Webgl.Float32Array.from_float_list(b);
    c;
  e =
    f = mat4.to_list(mvMatrix);
    g = Webgl.Float32Array.from_float_list(f);
    g;
  do Webgl.uniformMatrix4fv(gl, shaderProgram.pMatrixUniform, false, a);
  do Webgl.uniformMatrix4fv(gl, shaderProgram.mvMatrixUniform, false, e);
  normalMatrix = mat3.create();
  do mat4.toInverseMat3(mvMatrix, normalMatrix);
  do mat3.transpose(normalMatrix, normalMatrix);
  do Webgl.uniformMatrix3fv(gl, shaderProgram.nMatrixUniform, false, Webgl.Float32Array.from_float_list(mat3.to_list(normalMatrix)));
  void
;

setup_boxes(eng) =
  sep_largeur = 2;
  g(x, y, w, h) = { ~x; ~y; ~w; ~h } ;
  compute_left_right(x) = if ((mod(x, 2)) == 0) then
      a = (x / 2) - 1;
      (a, a)
    else
      b = (x / 2);
      (b - 1, b);
  (w_l, w_r) = compute_left_right(eng.canvas.width);
  (h_u, h_d) = compute_left_right(eng.canvas.height);
  { _YX=g(0, h_d+sep_largeur, w_l, h_u); _YZ=g(w_l+sep_largeur, h_d+sep_largeur, w_r, h_u);
    _ZX=g(0, 0, w_l, h_d); _3D=g(w_l+sep_largeur, 0, w_r, h_d) }
;

drawScene_for_a_viewport(eng, viewport, eye, up, squareVertexPositionBuffer) =
  gl = eng.context; shaderProgram = eng.shaderProgram; repcoords = eng.static_buffers.repcoords;
  do Webgl.viewport(gl, viewport.x, viewport.y, viewport.w, viewport.h);
  pMatrix =
    tmp_pMatrix = mat4.create();
    do mat4.perspective(45., float_of_int(eng.canvas.width) / float_of_int(eng.canvas.height), 0.1, 100.0, tmp_pMatrix);
    c = mat4.create() ;
    do mat4.lookAt(vec3.from_public(eye), vec3.from_public((0.0, 0.0, 0.0)), vec3.from_public(up), c);
    do mat4.multiply(tmp_pMatrix, c, tmp_pMatrix);
    tmp_pMatrix;
  mvMatrix =
    tmp_mvMatrix = mat4.create();
    do mat4.identity(tmp_mvMatrix);
    tmp_mvMatrix;
  do Webgl.uniform1i(gl, shaderProgram.useLightingUniform, 1); // 1 = true
  do Webgl.uniform3f(gl, shaderProgram.ambientColorUniform, 0.4, 0.4, 0.4);
  do Webgl.uniform3f(gl, shaderProgram.lightingDirectionUniform, 0.85, 0.8, 0.75);
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), squareVertexPositionBuffer.positions);
  do Webgl.vertexAttribPointer(gl, shaderProgram.vertexPositionAttribute, squareVertexPositionBuffer.itemSize, Webgl.FLOAT(gl), false, 0, 0);
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), squareVertexPositionBuffer.normals);
  do Webgl.vertexAttribPointer(gl, shaderProgram.vertexNormalAttribute, squareVertexPositionBuffer.itemSize, Webgl.FLOAT(gl), false, 0, 0);
  do Webgl.bindBuffer(gl, Webgl.ELEMENT_ARRAY_BUFFER(gl), squareVertexPositionBuffer.indexs);
  do setMatrixUniforms(gl, shaderProgram, pMatrix, mvMatrix);
  do Webgl.drawElements(gl, Webgl.TRIANGLES(gl), 36, Webgl.UNSIGNED_SHORT(gl), 0);

  draw_rep(r, g, b, rep) =
    do Webgl.uniform1i(gl, shaderProgram.useLightingUniform, 0); // 0 = false
    do Webgl.uniform3f(gl, shaderProgram.ambientColorUniform, r, g, b);
    do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), rep.positions);
    do Webgl.vertexAttribPointer(gl, shaderProgram.vertexPositionAttribute, rep.itemSize, Webgl.FLOAT(gl), false, 0, 0);
    do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), rep.normals);
    do Webgl.vertexAttribPointer(gl, shaderProgram.vertexNormalAttribute, rep.itemSize, Webgl.FLOAT(gl), false, 0, 0);
    do Webgl.drawArrays(gl, Webgl.LINES(gl), 0, rep.numItems);
    void ;
  do draw_rep(1.0, 0.0, 0.0, repcoords.x);
  do draw_rep(0.0, 1.0, 0.0, repcoords.y);
  do draw_rep(0.0, 0.0, 1.0, repcoords.z);

  void
;

drawScene_and_register(eng, squareVertexPositionBuffer) =
  viewbox = setup_boxes(eng) ;
  rec aux(eng, squareVertexPositionBuffer) =
    gl = eng.context;
    do Webgl.clear(gl, Webgl.GLbitfield_OR(Webgl.COLOR_BUFFER_BIT(gl), Webgl.DEPTH_BUFFER_BIT(gl)));
    do drawScene_for_a_viewport(eng, viewbox._YX, (0.0, 0.0, 15.0), (0.0, 1.0, 0.0), squareVertexPositionBuffer);
    do drawScene_for_a_viewport(eng, viewbox._YZ, (-15.0, 0.0, 0.0), (0.0, 1.0, 0.0), squareVertexPositionBuffer);
    do drawScene_for_a_viewport(eng, viewbox._ZX, (0.0, -15.0, 0.0), (0.0, 0.0, 1.0), squareVertexPositionBuffer);
    do drawScene_for_a_viewport(eng, viewbox._3D, (15.0, 10.0, 15.0), (0.0, 1.0, 0.0), squareVertexPositionBuffer);
    do RequestAnimationFrame.request((_ -> aux(eng, squareVertexPositionBuffer)), #{id_canvas_area});
    void
    ;
  aux(eng, squareVertexPositionBuffer)
;

initGL(canvas_sel, width, height) : void =
  match Webgl.getContext(Dom.of_selection(canvas_sel), "experimental-webgl") with
  | { some=context } ->
    gl = context;
    eng : engine =
      start = @openrecord({ context=gl; canvas={ selector=canvas_sel; ~width; ~height } });
      start = { start with shaderProgram=initShaders(gl) };
      { start with static_buffers.repcoords=
        { x=initLineXBuffers(gl, {x}); y=initLineXBuffers(gl, {y}); z=initLineXBuffers(gl, {z}) } };
    squareVertexPositionBuffer = initBuffers(gl);
    //Clear screen and make everything light gray
    do Webgl.clearColor(gl, 0.9, 0.9, 0.9, 1.0);
    //we should do depth testing so that things drawn behind other
    //things should be hidden by the things in front of them).
    do Webgl.clearDepth(gl, 1.0);
    do Webgl.enable(gl, Webgl.DEPTH_TEST(gl));
    do Webgl.depthFunc(gl, Webgl.LEQUAL(gl));
    do drawScene_and_register(eng, squareVertexPositionBuffer);
    void
  | { none } -> error("no context found")
  end ;


removing light from 2d view

removing light from 2d view

@private type my_custom_shaderProgram = {
  program: Webgl.WebGLProgram;
  vertexPositionAttribute: Webgl.GLint;
  vertexNormalAttribute: Webgl.GLint;
  pMatrixUniform: Webgl.WebGLUniformLocation;
  mvMatrixUniform: Webgl.WebGLUniformLocation;
  nMatrixUniform: Webgl.WebGLUniformLocation;
  ambientColorUniform: Webgl.WebGLUniformLocation;
  lightingDirectionUniform: Webgl.WebGLUniformLocation;
  useLightingUniform: Webgl.WebGLUniformLocation
};

@private type static_buffer = {
  positions: Webgl.WebGLBuffer;
  itemSize: int; numItems: int;
  normals: Webgl.WebGLBuffer
};

@private type engine = {
  context: Webgl.Context.private;
  canvas: { selector:dom; width: int; height: int };
  shaderProgram: my_custom_shaderProgram
  static_buffers: { repcoords: { x:static_buffer; y:static_buffer; z:static_buffer } };
  framePickBuffer: Webgl.WebGLFramebuffer;
  scene: list((vec3, object));
  selector: dom
} ;

@client initPickBuffer(eng) =
  gl = eng.context;
  framePickBuffer = Webgl.createFramebuffer(gl);
  renderPickBuffer = Webgl.createRenderbuffer(gl);
  pickTexture = Webgl.createTexture(gl);
  do Webgl.bindTexture(gl, Webgl.TEXTURE_2D(gl), Option.some(pickTexture));
  tex = Webgl.Uint8Array.from_int_list([0, 0, 0]);
  do Webgl.texImage2D(gl, Webgl.TEXTURE_2D(gl), 0, Webgl.RGB(gl), eng.canvas.width, eng.canvas.height, 0, Webgl.RGB(gl), Webgl.UNSIGNED_BYTE(gl), Webgl.Uint8Array.to_ArrayBuffer(tex));
  do Webgl.bindFramebuffer(gl, Webgl.FRAMEBUFFER(gl), Option.some(framePickBuffer));
  do Webgl.bindRenderbuffer(gl, Webgl.RENDERBUFFER(gl), Option.some(renderPickBuffer));
  do Webgl.renderbufferStorage(gl, Webgl.RENDERBUFFER(gl), Webgl.DEPTH_COMPONENT16(gl), eng.canvas.width, eng.canvas.height);
  do Webgl.bindRenderbuffer(gl, Webgl.RENDERBUFFER(gl), Option.none);

  do Webgl.framebufferTexture2D(gl, Webgl.FRAMEBUFFER(gl), Webgl.COLOR_ATTACHMENT0(gl), Webgl.TEXTURE_2D(gl), pickTexture, 0);
  do Webgl.framebufferRenderbuffer(gl, Webgl.FRAMEBUFFER(gl), Webgl.DEPTH_ATTACHMENT(gl), Webgl.RENDERBUFFER(gl), renderPickBuffer);
  do Webgl.bindFramebuffer(gl, Webgl.FRAMEBUFFER(gl), Option.none);
  do Webgl.bindTexture(gl, Webgl.TEXTURE_2D(gl), Option.none);
  framePickBuffer
;

initShaders(gl) =
  f(e, str) =
    shader = Webgl.createShader(gl, e);
    do Webgl.shaderSource(gl, shader, str);
    do Webgl.compileShader(gl, shader);
    shader;
  fragmentShader = f(Webgl.FRAGMENT_SHADER(gl), CustomShaders.shader_fs);
  vertexShader = f(Webgl.VERTEX_SHADER(gl), CustomShaders.shader_vs);
  // TODO getShaderParameter
  shaderProgram = Webgl.createProgram(gl);
  do Webgl.attachShader(gl, shaderProgram, vertexShader);
  do Webgl.attachShader(gl, shaderProgram, fragmentShader);
  do Webgl.linkProgram(gl, shaderProgram);
  // TODO : getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
  do Webgl.useProgram(gl, shaderProgram);
  shaderProgram =
    vertexPositionAttribute = Webgl.getAttribLocation(gl, shaderProgram, "aVertexPosition");
    vertexNormalAttribute = Webgl.getAttribLocation(gl, shaderProgram, "aVertexNormal");
    do Webgl.enableVertexAttribArray(gl, vertexPositionAttribute);
    do Webgl.enableVertexAttribArray(gl, vertexNormalAttribute);
    { program = shaderProgram;
      ~vertexPositionAttribute;
      ~vertexNormalAttribute;
      pMatrixUniform = Webgl.getUniformLocation(gl, shaderProgram, "uPMatrix");
      mvMatrixUniform = Webgl.getUniformLocation(gl, shaderProgram, "uMVMatrix");
      nMatrixUniform = Webgl.getUniformLocation(gl, shaderProgram, "uNMatrix");
      ambientColorUniform = Webgl.getUniformLocation(gl, shaderProgram, "uAmbientColor");
      lightingDirectionUniform = Webgl.getUniformLocation(gl, shaderProgram, "uLightingDirection");
      useLightingUniform = Webgl.getUniformLocation(gl, shaderProgram, "uUseLighting");
    };
  shaderProgram
;

initLineXBuffers(gl, orient) =
  (vertices, vertexNormals) = match orient with
    | {x} -> ([ 0.0, 0.0, 0.0, 5.0, 0.0, 0.0 ], [ 2.5, 0.0, 0.0,        2.5, -1.0, 0.0 ])
    | {y} -> ([ 0.0, 0.0, 0.0, 0.0, 5.0, 0.0 ], [ 0.0, 2.5, 0.0,        -1.0, 2.5, 0.0 ])
    | {z} -> ([ 0.0, 0.0, 0.0, 0.0, 0.0, 5.0 ], [ 0.0, 0.0, 2.5,        0.0, -1.0, 2.5 ])
    end ;
  vertexPositionBuffer = Webgl.createBuffer(gl);
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), vertexPositionBuffer);
  do Webgl.bufferData(gl, Webgl.ARRAY_BUFFER(gl),
    Webgl.Float32Array.to_ArrayBuffer(Webgl.Float32Array.from_float_list(vertices)),
    Webgl.STATIC_DRAW(gl));
  vertexNormalBuffer = Webgl.createBuffer(gl);
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), vertexNormalBuffer);
  do Webgl.bufferData(gl, Webgl.ARRAY_BUFFER(gl),
    Webgl.Float32Array.to_ArrayBuffer(Webgl.Float32Array.from_float_list(vertexNormals)),
    Webgl.STATIC_DRAW(gl));
  { positions=vertexPositionBuffer; itemSize=3; numItems=2; normals=vertexNormalBuffer }
;

setMatrixUniforms(gl, shaderProgram, pMatrix, mvMatrix) =
  a =
    b = mat4.to_list(pMatrix);
    c = Webgl.Float32Array.from_float_list(b);
    c;
  e =
    f = mat4.to_list(mvMatrix);
    g = Webgl.Float32Array.from_float_list(f);
    g;
  do Webgl.uniformMatrix4fv(gl, shaderProgram.pMatrixUniform, false, a);
  do Webgl.uniformMatrix4fv(gl, shaderProgram.mvMatrixUniform, false, e);
  normalMatrix = mat3.create();
  do mat4.toInverseMat3(mvMatrix, normalMatrix);
  do mat3.transpose(normalMatrix, normalMatrix);
  do Webgl.uniformMatrix3fv(gl, shaderProgram.nMatrixUniform, false, Webgl.Float32Array.from_float_list(mat3.to_list(normalMatrix)));
  void
;

setup_boxes(eng) =
  sep_largeur = 2;
  g(x, y, w, h) = { ~x; ~y; ~w; ~h } ;
  compute_left_right(x) = if ((mod(x, 2)) == 0) then
      a = (x / 2) - 1;
      (a, a)
    else
      b = (x / 2);
      (b - 1, b);
  (w_l, w_r) = compute_left_right(eng.canvas.width);
  (h_u, h_d) = compute_left_right(eng.canvas.height);
  { _YX=g(0, h_d+sep_largeur, w_l, h_u); _YZ=g(w_l+sep_largeur, h_d+sep_largeur, w_r, h_u);
    _ZX=g(0, 0, w_l, h_d); _3D=g(w_l+sep_largeur, 0, w_r, h_d) }
;

drawScene_for_a_viewport(eng, who, viewport, eye, up, scene, mode) =
  gl = eng.context; shaderProgram = eng.shaderProgram; repcoords = eng.static_buffers.repcoords;
  do Webgl.viewport(gl, viewport.x, viewport.y, viewport.w, viewport.h);
  pMatrix =
    tmp_pMatrix = mat4.create();
    match who with
    | {_YX} ->
      do mat4.ortho(-7., 7., -7., 7., -10., 10., tmp_pMatrix);
      tmp_pMatrix
    | {_YZ} ->
      do mat4.ortho(-7., 7., -7., 7., -10., 10., tmp_pMatrix);
      mat4.rotateY(tmp_pMatrix, (90. * Math.PI / 180.), tmp_pMatrix)
    | {_ZX} ->
      do mat4.ortho(-7., 7., -7., 7., -10., 10., tmp_pMatrix);
      mat4.rotateX(tmp_pMatrix, (90. * Math.PI / 180.), tmp_pMatrix)
    | {_3D} ->
      do mat4.perspective(45., float_of_int(eng.canvas.width) / float_of_int(eng.canvas.height), 0.1, 100.0, tmp_pMatrix);
      c = mat4.create() ;
      do mat4.lookAt(vec3.from_public(eye), vec3.from_public((0.0, 0.0, 0.0)), vec3.from_public(up), c);
      do mat4.multiply(tmp_pMatrix, c, tmp_pMatrix);
      tmp_pMatrix
    end ;
  mvMatrix =
    tmp_mvMatrix = mat4.create();
    do mat4.identity(tmp_mvMatrix);
    Stack.push(Stack.create(), tmp_mvMatrix);
  do setMatrixUniforms(gl, shaderProgram, pMatrix, Stack.peek(mvMatrix));
  draw_rep(r, g, b, rep) =
    do Webgl.uniform3f(gl, shaderProgram.ambientColorUniform, r, g, b);
    do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), rep.positions);
    do Webgl.vertexAttribPointer(gl, shaderProgram.vertexPositionAttribute, rep.itemSize, Webgl.FLOAT(gl), false, 0, 0);
    do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), rep.normals);
    do Webgl.vertexAttribPointer(gl, shaderProgram.vertexNormalAttribute, rep.itemSize, Webgl.FLOAT(gl), false, 0, 0);
    do Webgl.drawArrays(gl, Webgl.LINES(gl), 0, rep.numItems);
    void ;

  _ =
    match mode with
    | {normal} ->
      do Webgl.uniform1i(gl, shaderProgram.useLightingUniform, 0); // 0 = false
      do draw_rep(1.0, 0.0, 0.0, repcoords.x);
      do draw_rep(0.0, 1.0, 0.0, repcoords.y);
      do draw_rep(0.0, 0.0, 1.0, repcoords.z);
      do match who with
        | {_3D} ->
          do Webgl.uniform1i(gl, shaderProgram.useLightingUniform, 1); // 1 = true
          Webgl.uniform3f(gl, shaderProgram.lightingDirectionUniform, 0.85, 0.8, 0.75)
        | _ -> void end;
      List.iter(((pos, object) -> display(eng, pMatrix, mvMatrix, pos, object, false)), scene)
    | {pick} ->
      do Webgl.bindFramebuffer(gl, Webgl.FRAMEBUFFER(gl), Option.some(eng.framePickBuffer));
      do Webgl.clear(gl, Webgl.GLbitfield_OR(Webgl.COLOR_BUFFER_BIT(gl), Webgl.DEPTH_BUFFER_BIT(gl)));
      do Webgl.uniform1i(gl, shaderProgram.useLightingUniform, 0); // 0 = false;
      do List.iter(((pos, object) -> display(eng, pMatrix, mvMatrix, pos, object, true)), scene);
      void
    end ;

  (pMatrix, mvMatrix)
;

drawScene_and_register(org_eng, get_scene : (->Modeler.scene), get_mode) =
  viewbox = setup_boxes(org_eng) ;
  rec aux(eng) =
    gl = eng.context;
    (eng, scene) =
      f(p) =
        match List.find((z_in_mem -> z_in_mem.f2.id == p.id), eng.scene) with
        | { some=in_mem } -> { in_mem with f1=p.cube }
        | { none } -> (p.cube, Cube.create(gl, p.id))
        end;
      scene = List.map(f, get_scene());
      ({ eng with ~scene }, scene);
    do match get_mode() with
    | {pick=pos; ~cont} ->
      //do Log.debug("Picking", "...");
      _ = drawScene_for_a_viewport(eng, {_YX}, viewbox._YX, (0.0, 0.0, 15.0), (0.0, 1.0, 0.0), scene, {pick});
      _ = drawScene_for_a_viewport(eng, {_YZ}, viewbox._YZ, (-15.0, 0.0, 0.0), (0.0, 1.0, 0.0), scene, {pick});
      (pMatrix, s) = drawScene_for_a_viewport(eng, {_ZX}, viewbox._ZX, (0.0, -15.0, 0.0), (0.0, 0.0, 1.0), scene, {pick});
      //(pMatrix, s) = drawScene_for_a_viewport(eng, {_3D}, viewbox._3D, (10.0, 5.0, 15.0), (0.0, 1.0, 0.0), scene, {pick});
      x = (float_of_int(pos.x_px - viewbox._ZX.x) / float_of_int(viewbox._ZX.w)) * 2.0 - 1.0;
      y = (float_of_int(pos.y_px - viewbox._ZX.y) / float_of_int(viewbox._ZX.h)) * 2.0 - 1.0;
      mvMatrix = Stack.peek(s) ;
      do mat4.multiply(pMatrix, mvMatrix, mvMatrix);
      do mat4.inverse(mvMatrix, mvMatrix);
      v1 = vec4.from_public((x, y, 1.0, 1.0));
      v2 = vec4.from_public((9.9, 9.9, 9.9, 9.9));
      do mat4.multiplyVec4(mvMatrix, v1, v2);
      v22 = vec4.to_public(v2);
      //v22 = { v22 with f2=0.0 };
      v2 = (v22.f1 / v22.f4, v22.f2 / v22.f4, v22.f3 / v22.f4, v22.f4);
      data = Webgl.Uint8Array.from_int_list(List.init((_->123), 4));
      do Webgl.readPixels(gl, pos.x_px, pos.y_px, 1, 1, Webgl.RGBA(gl), Webgl.UNSIGNED_BYTE(gl), Webgl.Uint8Array.to_ArrayBuffer(data));
      pickedColor = match Webgl.Uint8Array.to_int_list(data) with
        | [r, g, b, _] -> (r, g, b)
        | _ -> error("Picking failure")
        end ;
      do Log.debug("Picking", "Color is: { pickedColor }; v1={ vec4.str(v1) }, \t v2={ v2 }");
      //do jlog("Color is: { pickedColor }; v={ vec3.str(v) }");
      possible_target =
        (r, g, b) = pickedColor;
        f(z) = (z.f2.picking_color == (float_of_int(r) / 255., float_of_int(g) / 255., float_of_int(b) / 255.)) ;
        Option.map((u -> u.f2.id), List.find(f, eng.scene));
      do Webgl.bindFramebuffer(gl, Webgl.FRAMEBUFFER(gl), Option.none);
      cont({ mousedown; x=v2.f1; z=v2.f3; ~possible_target })
    | {normal} ->
      do Webgl.clear(gl, Webgl.GLbitfield_OR(Webgl.COLOR_BUFFER_BIT(gl), Webgl.DEPTH_BUFFER_BIT(gl)));
      _ = drawScene_for_a_viewport(eng, {_YX}, viewbox._YX, (0.0, 0.0, 15.0), (0.0, 1.0, 0.0), scene, {normal});
      _ = drawScene_for_a_viewport(eng, {_YZ}, viewbox._YZ, (-15.0, 0.0, 0.0), (0.0, 1.0, 0.0), scene, {normal});
      _ = drawScene_for_a_viewport(eng, {_ZX}, viewbox._ZX, (0.0, -15.0, 0.0), (0.0, 0.0, 1.0), scene, {normal});
      _ = drawScene_for_a_viewport(eng, {_3D}, viewbox._3D, (10.0, 5.0, 15.0), (0.0, 1.0, 0.0), scene, {normal});
      void
    end ;
    do RequestAnimationFrame.request((_ -> aux(eng)), eng.selector);
    void
    ;
  aux(org_eng)
;

initGL(canvas_sel, width, height, get_scene, mouse_listener) : outcome =
  match WebGLUtils.setupWebGL_with_custom_failure(Dom.of_selection(canvas_sel)) with
  | { ok=context } ->
    mode = Mutable.make_client({normal});
    is_picking(m) = match m with | { pick=_; cont=_ } -> true | _ -> false end;
    _ =
      handler(e) =
        m_pos = // we transform the pos to be relative to the upper leftcorner of the canvas
          c_pos = Dom.get_offset(canvas_sel);
          rel = e.mouse_position_on_page;
          { x_px=max(rel.x_px - c_pos.x_px, 0); y_px=max(rel.y_px - c_pos.y_px, 0) };
        // now with gl the origin will be at the lower left corner
        gl_pos = { x_px=min(max(m_pos.x_px,0), height-1); y_px=min(max(height - 1 - m_pos.y_px, 0), width-1) };
        cont(e) =
          do mode.set({normal});
          mouse_listener(e);
        do if not(is_picking(mode.get())) then mode.set({pick=gl_pos; ~cont});
        Log.debug("P", "[(,)-({m_pos.x_px},{m_pos.y_px})] {gl_pos.x_px}, {gl_pos.y_px}");
      Dom.bind(canvas_sel, { mousedown }, handler);
    gl = context;
    eng : engine =
      start = @openrecord({ context=gl; canvas={ selector=canvas_sel; ~width; ~height }; scene=List.empty; selector=canvas_sel });
      start = { start with shaderProgram=initShaders(gl) };
      start = { start with framePickBuffer=initPickBuffer(start) } ;
      { start with static_buffers.repcoords=
        { x=initLineXBuffers(gl, {x}); y=initLineXBuffers(gl, {y}); z=initLineXBuffers(gl, {z}) } };
    //Clear screen and make everything light gray
    do Webgl.clearColor(gl, 0.9, 0.9, 0.9, 1.0);
    //we should do depth testing so that things drawn behind other
    //things should be hidden by the things in front of them).
    do Webgl.clearDepth(gl, 1.0);
    do Webgl.enable(gl, Webgl.DEPTH_TEST(gl));
    do Webgl.depthFunc(gl, Webgl.LEQUAL(gl));
    do drawScene_and_register(eng, get_scene, mode.get);
    { success }
  | { ~ko } -> { failure=ko }
  end ;

@private type my_custom_shaderProgram = {
  program: Webgl.WebGLProgram;
  vertexPositionAttribute: Webgl.GLint;
  vertexNormalAttribute: Webgl.GLint;
  pMatrixUniform: Webgl.WebGLUniformLocation;
  mvMatrixUniform: Webgl.WebGLUniformLocation;
  nMatrixUniform: Webgl.WebGLUniformLocation;
  ambientColorUniform: Webgl.WebGLUniformLocation;
  lightingDirectionUniform: Webgl.WebGLUniformLocation;
  useLightingUniform: Webgl.WebGLUniformLocation
};

@private type static_buffer = {
  positions: Webgl.WebGLBuffer;
  itemSize: int; numItems: int;
  normals: Webgl.WebGLBuffer
};

@private type engine = {
  context: Webgl.Context.private;
  canvas: { selector:dom; width: int; height: int };
  shaderProgram: my_custom_shaderProgram
  static_buffers: { repcoords: { x:static_buffer; y:static_buffer; z:static_buffer } };
  framePickBuffer: Webgl.WebGLFramebuffer;
  scene: list((vec3, object));
  selector: dom
} ;

@client initPickBuffer(eng) =
  gl = eng.context;
  framePickBuffer = Webgl.createFramebuffer(gl);
  renderPickBuffer = Webgl.createRenderbuffer(gl);
  pickTexture = Webgl.createTexture(gl);
  do Webgl.bindTexture(gl, Webgl.TEXTURE_2D(gl), Option.some(pickTexture));
  tex = Webgl.Uint8Array.from_int_list([0, 0, 0]);
  do Webgl.texImage2D(gl, Webgl.TEXTURE_2D(gl), 0, Webgl.RGB(gl), eng.canvas.width, eng.canvas.height, 0, Webgl.RGB(gl), Webgl.UNSIGNED_BYTE(gl), Webgl.Uint8Array.to_ArrayBuffer(tex));
  do Webgl.bindFramebuffer(gl, Webgl.FRAMEBUFFER(gl), Option.some(framePickBuffer));
  do Webgl.bindRenderbuffer(gl, Webgl.RENDERBUFFER(gl), Option.some(renderPickBuffer));
  do Webgl.renderbufferStorage(gl, Webgl.RENDERBUFFER(gl), Webgl.DEPTH_COMPONENT16(gl), eng.canvas.width, eng.canvas.height);
  do Webgl.bindRenderbuffer(gl, Webgl.RENDERBUFFER(gl), Option.none);

  do Webgl.framebufferTexture2D(gl, Webgl.FRAMEBUFFER(gl), Webgl.COLOR_ATTACHMENT0(gl), Webgl.TEXTURE_2D(gl), pickTexture, 0);
  do Webgl.framebufferRenderbuffer(gl, Webgl.FRAMEBUFFER(gl), Webgl.DEPTH_ATTACHMENT(gl), Webgl.RENDERBUFFER(gl), renderPickBuffer);
  do Webgl.bindFramebuffer(gl, Webgl.FRAMEBUFFER(gl), Option.none);
  do Webgl.bindTexture(gl, Webgl.TEXTURE_2D(gl), Option.none);
  framePickBuffer
;

initShaders(gl) =
  f(e, str) =
    shader = Webgl.createShader(gl, e);
    do Webgl.shaderSource(gl, shader, str);
    do Webgl.compileShader(gl, shader);
    shader;
  fragmentShader = f(Webgl.FRAGMENT_SHADER(gl), CustomShaders.shader_fs);
  vertexShader = f(Webgl.VERTEX_SHADER(gl), CustomShaders.shader_vs);
  // TODO getShaderParameter
  shaderProgram = Webgl.createProgram(gl);
  do Webgl.attachShader(gl, shaderProgram, vertexShader);
  do Webgl.attachShader(gl, shaderProgram, fragmentShader);
  do Webgl.linkProgram(gl, shaderProgram);
  // TODO : getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
  do Webgl.useProgram(gl, shaderProgram);
  shaderProgram =
    vertexPositionAttribute = Webgl.getAttribLocation(gl, shaderProgram, "aVertexPosition");
    vertexNormalAttribute = Webgl.getAttribLocation(gl, shaderProgram, "aVertexNormal");
    do Webgl.enableVertexAttribArray(gl, vertexPositionAttribute);
    do Webgl.enableVertexAttribArray(gl, vertexNormalAttribute);
    { program = shaderProgram;
      ~vertexPositionAttribute;
      ~vertexNormalAttribute;
      pMatrixUniform = Webgl.getUniformLocation(gl, shaderProgram, "uPMatrix");
      mvMatrixUniform = Webgl.getUniformLocation(gl, shaderProgram, "uMVMatrix");
      nMatrixUniform = Webgl.getUniformLocation(gl, shaderProgram, "uNMatrix");
      ambientColorUniform = Webgl.getUniformLocation(gl, shaderProgram, "uAmbientColor");
      lightingDirectionUniform = Webgl.getUniformLocation(gl, shaderProgram, "uLightingDirection");
      useLightingUniform = Webgl.getUniformLocation(gl, shaderProgram, "uUseLighting");
    };
  shaderProgram
;

initLineXBuffers(gl, orient) =
  (vertices, vertexNormals) = match orient with
    | {x} -> ([ 0.0, 0.0, 0.0, 5.0, 0.0, 0.0 ], [ 2.5, 0.0, 0.0,        2.5, -1.0, 0.0 ])
    | {y} -> ([ 0.0, 0.0, 0.0, 0.0, 5.0, 0.0 ], [ 0.0, 2.5, 0.0,        -1.0, 2.5, 0.0 ])
    | {z} -> ([ 0.0, 0.0, 0.0, 0.0, 0.0, 5.0 ], [ 0.0, 0.0, 2.5,        0.0, -1.0, 2.5 ])
    end ;
  vertexPositionBuffer = Webgl.createBuffer(gl);
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), vertexPositionBuffer);
  do Webgl.bufferData(gl, Webgl.ARRAY_BUFFER(gl),
    Webgl.Float32Array.to_ArrayBuffer(Webgl.Float32Array.from_float_list(vertices)),
    Webgl.STATIC_DRAW(gl));
  vertexNormalBuffer = Webgl.createBuffer(gl);
  do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), vertexNormalBuffer);
  do Webgl.bufferData(gl, Webgl.ARRAY_BUFFER(gl),
    Webgl.Float32Array.to_ArrayBuffer(Webgl.Float32Array.from_float_list(vertexNormals)),
    Webgl.STATIC_DRAW(gl));
  { positions=vertexPositionBuffer; itemSize=3; numItems=2; normals=vertexNormalBuffer }
;

setMatrixUniforms(gl, shaderProgram, pMatrix, mvMatrix) =
  a =
    b = mat4.to_list(pMatrix);
    c = Webgl.Float32Array.from_float_list(b);
    c;
  e =
    f = mat4.to_list(mvMatrix);
    g = Webgl.Float32Array.from_float_list(f);
    g;
  do Webgl.uniformMatrix4fv(gl, shaderProgram.pMatrixUniform, false, a);
  do Webgl.uniformMatrix4fv(gl, shaderProgram.mvMatrixUniform, false, e);
  normalMatrix = mat3.create();
  do mat4.toInverseMat3(mvMatrix, normalMatrix);
  do mat3.transpose(normalMatrix, normalMatrix);
  do Webgl.uniformMatrix3fv(gl, shaderProgram.nMatrixUniform, false, Webgl.Float32Array.from_float_list(mat3.to_list(normalMatrix)));
  void
;

setup_boxes(eng) =
  sep_largeur = 2;
  g(x, y, w, h) = { ~x; ~y; ~w; ~h } ;
  compute_left_right(x) = if ((mod(x, 2)) == 0) then
      a = (x / 2) - 1;
      (a, a)
    else
      b = (x / 2);
      (b - 1, b);
  (w_l, w_r) = compute_left_right(eng.canvas.width);
  (h_u, h_d) = compute_left_right(eng.canvas.height);
  { _YX=g(0, h_d+sep_largeur, w_l, h_u); _YZ=g(w_l+sep_largeur, h_d+sep_largeur, w_r, h_u);
    _ZX=g(0, 0, w_l, h_d); _3D=g(w_l+sep_largeur, 0, w_r, h_d) }
;

drawScene_for_a_viewport(eng, who, viewport, eye, up, scene, mode) =
  gl = eng.context; shaderProgram = eng.shaderProgram; repcoords = eng.static_buffers.repcoords;
  do Webgl.viewport(gl, viewport.x, viewport.y, viewport.w, viewport.h);
  pMatrix =
    tmp_pMatrix = mat4.create();
    match who with
    | {_YX} ->
      do mat4.ortho(-7., 7., -7., 7., -10., 10., tmp_pMatrix);
      tmp_pMatrix
    | {_YZ} ->
      do mat4.ortho(-7., 7., -7., 7., -10., 10., tmp_pMatrix);
      mat4.rotateY(tmp_pMatrix, (90. * Math.PI / 180.), tmp_pMatrix)
    | {_ZX} ->
      do mat4.ortho(-7., 7., -7., 7., -10., 10., tmp_pMatrix);
      mat4.rotateX(tmp_pMatrix, (90. * Math.PI / 180.), tmp_pMatrix)
    | {_3D} ->
      do mat4.perspective(45., float_of_int(eng.canvas.width) / float_of_int(eng.canvas.height), 0.1, 100.0, tmp_pMatrix);
      c = mat4.create() ;
      do mat4.lookAt(vec3.from_public(eye), vec3.from_public((0.0, 0.0, 0.0)), vec3.from_public(up), c);
      do mat4.multiply(tmp_pMatrix, c, tmp_pMatrix);
      tmp_pMatrix
    end ;
  mvMatrix =
    tmp_mvMatrix = mat4.create();
    do mat4.identity(tmp_mvMatrix);
    Stack.push(Stack.create(), tmp_mvMatrix);
  do setMatrixUniforms(gl, shaderProgram, pMatrix, Stack.peek(mvMatrix));
  draw_rep(r, g, b, rep) =
    do Webgl.uniform1i(gl, shaderProgram.useLightingUniform, 0); // 0 = false
    do Webgl.uniform3f(gl, shaderProgram.ambientColorUniform, r, g, b);
    do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), rep.positions);
    do Webgl.vertexAttribPointer(gl, shaderProgram.vertexPositionAttribute, rep.itemSize, Webgl.FLOAT(gl), false, 0, 0);
    do Webgl.bindBuffer(gl, Webgl.ARRAY_BUFFER(gl), rep.normals);
    do Webgl.vertexAttribPointer(gl, shaderProgram.vertexNormalAttribute, rep.itemSize, Webgl.FLOAT(gl), false, 0, 0);
    do Webgl.drawArrays(gl, Webgl.LINES(gl), 0, rep.numItems);
    void ;

  _ =
    match mode with
    | {normal} ->
      do draw_rep(1.0, 0.0, 0.0, repcoords.x);
      do draw_rep(0.0, 1.0, 0.0, repcoords.y);
      do draw_rep(0.0, 0.0, 1.0, repcoords.z);

      do Webgl.uniform1i(gl, shaderProgram.useLightingUniform, 1); // 1 = true
      do Webgl.uniform3f(gl, shaderProgram.lightingDirectionUniform, 0.85, 0.8, 0.75);
      List.iter(((pos, object) -> display(eng, pMatrix, mvMatrix, pos, object, false)), scene)
    | {pick} ->
      do Webgl.bindFramebuffer(gl, Webgl.FRAMEBUFFER(gl), Option.some(eng.framePickBuffer));
      do Webgl.clear(gl, Webgl.GLbitfield_OR(Webgl.COLOR_BUFFER_BIT(gl), Webgl.DEPTH_BUFFER_BIT(gl)));
      do Webgl.uniform1i(gl, shaderProgram.useLightingUniform, 0); // 0 = false;
      do List.iter(((pos, object) -> display(eng, pMatrix, mvMatrix, pos, object, true)), scene);
      void
    end ;

  (pMatrix, mvMatrix)
;

drawScene_and_register(org_eng, get_scene : (->Modeler.scene), get_mode) =
  viewbox = setup_boxes(org_eng) ;
  rec aux(eng) =
    gl = eng.context;
    (eng, scene) =
      f(p) =
        match List.find((z_in_mem -> z_in_mem.f2.id == p.id), eng.scene) with
        | { some=in_mem } -> { in_mem with f1=p.cube }
        | { none } -> (p.cube, Cube.create(gl, p.id))
        end;
      scene = List.map(f, get_scene());
      ({ eng with ~scene }, scene);
    do match get_mode() with
    | {pick=pos; ~cont} ->
      //do Log.debug("Picking", "...");
      _ = drawScene_for_a_viewport(eng, {_YX}, viewbox._YX, (0.0, 0.0, 15.0), (0.0, 1.0, 0.0), scene, {pick});
      _ = drawScene_for_a_viewport(eng, {_YZ}, viewbox._YZ, (-15.0, 0.0, 0.0), (0.0, 1.0, 0.0), scene, {pick});
      (pMatrix, s) = drawScene_for_a_viewport(eng, {_ZX}, viewbox._ZX, (0.0, -15.0, 0.0), (0.0, 0.0, 1.0), scene, {pick});
      //(pMatrix, s) = drawScene_for_a_viewport(eng, {_3D}, viewbox._3D, (10.0, 5.0, 15.0), (0.0, 1.0, 0.0), scene, {pick});
      x = (float_of_int(pos.x_px - viewbox._ZX.x) / float_of_int(viewbox._ZX.w)) * 2.0 - 1.0;
      y = (float_of_int(pos.y_px - viewbox._ZX.y) / float_of_int(viewbox._ZX.h)) * 2.0 - 1.0;
      mvMatrix = Stack.peek(s) ;
      do mat4.multiply(pMatrix, mvMatrix, mvMatrix);
      do mat4.inverse(mvMatrix, mvMatrix);
      v1 = vec4.from_public((x, y, 1.0, 1.0));
      v2 = vec4.from_public((9.9, 9.9, 9.9, 9.9));
      do mat4.multiplyVec4(mvMatrix, v1, v2);
      v22 = vec4.to_public(v2);
      //v22 = { v22 with f2=0.0 };
      v2 = (v22.f1 / v22.f4, v22.f2 / v22.f4, v22.f3 / v22.f4, v22.f4);
      data = Webgl.Uint8Array.from_int_list(List.init((_->123), 4));
      do Webgl.readPixels(gl, pos.x_px, pos.y_px, 1, 1, Webgl.RGBA(gl), Webgl.UNSIGNED_BYTE(gl), Webgl.Uint8Array.to_ArrayBuffer(data));
      pickedColor = match Webgl.Uint8Array.to_int_list(data) with
        | [r, g, b, _] -> (r, g, b)
        | _ -> error("Picking failure")
        end ;
      do Log.debug("Picking", "Color is: { pickedColor }; v1={ vec4.str(v1) }, \t v2={ v2 }");
      //do jlog("Color is: { pickedColor }; v={ vec3.str(v) }");
      possible_target =
        (r, g, b) = pickedColor;
        f(z) = (z.f2.picking_color == (float_of_int(r) / 255., float_of_int(g) / 255., float_of_int(b) / 255.)) ;
        Option.map((u -> u.f2.id), List.find(f, eng.scene));
      do Webgl.bindFramebuffer(gl, Webgl.FRAMEBUFFER(gl), Option.none);
      cont({ mousedown; x=v2.f1; z=v2.f3; ~possible_target })
    | {normal} ->
      do Webgl.clear(gl, Webgl.GLbitfield_OR(Webgl.COLOR_BUFFER_BIT(gl), Webgl.DEPTH_BUFFER_BIT(gl)));
      _ = drawScene_for_a_viewport(eng, {_YX}, viewbox._YX, (0.0, 0.0, 15.0), (0.0, 1.0, 0.0), scene, {normal});
      _ = drawScene_for_a_viewport(eng, {_YZ}, viewbox._YZ, (-15.0, 0.0, 0.0), (0.0, 1.0, 0.0), scene, {normal});
      _ = drawScene_for_a_viewport(eng, {_ZX}, viewbox._ZX, (0.0, -15.0, 0.0), (0.0, 0.0, 1.0), scene, {normal});
      _ = drawScene_for_a_viewport(eng, {_3D}, viewbox._3D, (10.0, 5.0, 15.0), (0.0, 1.0, 0.0), scene, {normal});
      void
    end ;
    do RequestAnimationFrame.request((_ -> aux(eng)), eng.selector);
    void
    ;
  aux(org_eng)
;

initGL(canvas_sel, width, height, get_scene, mouse_listener) : outcome =
  match WebGLUtils.setupWebGL_with_custom_failure(Dom.of_selection(canvas_sel)) with
  | { ok=context } ->
    mode = Mutable.make_client({normal});
    is_picking(m) = match m with | { pick=_; cont=_ } -> true | _ -> false end;
    _ =
      handler(e) =
        m_pos = // we transform the pos to be relative to the upper leftcorner of the canvas
          c_pos = Dom.get_offset(canvas_sel);
          rel = e.mouse_position_on_page;
          { x_px=max(rel.x_px - c_pos.x_px, 0); y_px=max(rel.y_px - c_pos.y_px, 0) };
        // now with gl the origin will be at the lower left corner
        gl_pos = { x_px=min(max(m_pos.x_px,0), height-1); y_px=min(max(height - 1 - m_pos.y_px, 0), width-1) };
        cont(e) =
          do mode.set({normal});
          mouse_listener(e);
        do if not(is_picking(mode.get())) then mode.set({pick=gl_pos; ~cont});
        Log.debug("P", "[(,)-({m_pos.x_px},{m_pos.y_px})] {gl_pos.x_px}, {gl_pos.y_px}");
      Dom.bind(canvas_sel, { mousedown }, handler);
    gl = context;
    eng : engine =
      start = @openrecord({ context=gl; canvas={ selector=canvas_sel; ~width; ~height }; scene=List.empty; selector=canvas_sel });
      start = { start with shaderProgram=initShaders(gl) };
      start = { start with framePickBuffer=initPickBuffer(start) } ;
      { start with static_buffers.repcoords=
        { x=initLineXBuffers(gl, {x}); y=initLineXBuffers(gl, {y}); z=initLineXBuffers(gl, {z}) } };
    //Clear screen and make everything light gray
    do Webgl.clearColor(gl, 0.9, 0.9, 0.9, 1.0);
    //we should do depth testing so that things drawn behind other
    //things should be hidden by the things in front of them).
    do Webgl.clearDepth(gl, 1.0);
    do Webgl.enable(gl, Webgl.DEPTH_TEST(gl));
    do Webgl.depthFunc(gl, Webgl.LEQUAL(gl));
    do drawScene_and_register(eng, get_scene, mode.get);
    { success }
  | { ~ko } -> { failure=ko }
  end ;