Engine: make mouse disappear after some inactivity

Author: panglesd

src/engine/dune

@@ -1,7 +1,7 @@
 (executable
  (modes js)
  (name main)
- (libraries communication brr normalization browser rescale table_of_content undoable step universe drawing))
+ (libraries communication brr normalization browser rescale table_of_content undoable step universe drawing mouse_disappearing))
 
 (rule
  (action

src/engine/main.ml

@@ -10,6 +10,7 @@ let start id step =
   (* TODO: move out of here (Later: Why?) *)
   let () = Rescale.setup_rescalers () in
   let () = Drawing.setup body in
+  let () = Mouse_disappearing.setup () in
   let initial_step =
     match step with
     | Some _ as step -> step

src/engine/mouse_disappearing/dune

@@ -0,0 +1,3 @@
+(library
+ (name mouse_disappearing)
+ (libraries brr))

src/engine/mouse_disappearing/mouse_disappearing.ml

@@ -0,0 +1,30 @@
+(*
+    document.body.style.cursor = "auto";
+    let timeOutIds = [];
+    document.body.addEventListener("mousemove", (ev) => {
+	timeOutIds.forEach((id) => { clearTimeout(id); });
+	document.body.style.cursor = "auto";
+	timeOutIds.push(setTimeout(() => { document.body.style.cursor = "none";}, 5000));
+    });
+ *)
+let body = Brr.Document.body Brr.G.document
+
+let show_cursor () =
+  Brr.El.set_inline_style Brr.El.Style.cursor (Jstr.v "auto") body
+
+let hide_cursor () =
+  Brr.El.set_inline_style Brr.El.Style.cursor (Jstr.v "none") body
+
+let setup () =
+  show_cursor ();
+  let timeout_id = ref None in
+  let _unlisten =
+    Brr.Ev.listen Brr.Ev.mousemove
+      (fun _ ->
+        (match !timeout_id with None -> () | Some id -> Brr.G.stop_timer id);
+        show_cursor ();
+        let id = Brr.G.set_timeout ~ms:5000 (fun _ -> hide_cursor ()) in
+        timeout_id := Some id)
+      (Brr.El.as_target body)
+  in
+  ()

src/engine/mouse_disappearing/mouse_disappearing.mli

@@ -0,0 +1 @@
+val setup : unit -> unit