Modify the source buffer so that the filename is used for selecting syntax...

Modify the source buffer so that the filename is used for selecting syntax highlighting rather than always using why.

This ensures that C files (coming from Jessie) are not uniformly blue due to pointer deferencing "(*ptr)".
For unrecognized files (e.g. Jesse files), the IDE falls back to the old approach, that is, using Why highlighting.

src/ide/newmain.ml

@@ -80,7 +80,7 @@ let fname = match !file with
   | Some f ->
       f
 
-let lang =
+let (why_lang, any_lang) =
   let main = get_main () in
   let load_path = Filename.concat (datadir main) "lang" in
   let languages_manager =
@@ -88,12 +88,18 @@ let lang =
   in
   languages_manager#set_search_path
     (load_path :: languages_manager#search_path);
-  match languages_manager#language "why" with
+  let why_lang =
+    match languages_manager#language "why" with
     | None ->
         Format.eprintf "language file for 'why' not found in directory %s@."
           load_path;
         exit 1
-    | Some _ as l -> l
+    | Some _ as l -> l in
+  let any_lang filename =
+    match languages_manager#guess_language ~filename () with
+    | None -> why_lang
+    | Some _ as l -> l in
+  (why_lang, any_lang)
 
 let source_text fname =
   let ic = open_in fname in
@@ -1078,7 +1084,7 @@ let task_view =
     ~height:gconfig.task_height
     ()
 
-let () = task_view#source_buffer#set_language lang
+let () = task_view#source_buffer#set_language why_lang
 let () = task_view#set_highlight_current_line true
 
 (***************)
@@ -1108,7 +1114,7 @@ let source_view =
 (*
   source_view#misc#modify_font_by_name font_name;
 *)
-let () = source_view#source_buffer#set_language lang
+let () = source_view#source_buffer#set_language None
 let () = source_view#set_highlight_current_line true
 (*
 let () = source_view#source_buffer#set_text (source_text fname)
@@ -1155,6 +1161,7 @@ let scroll_to_loc ?(yalign=0.0) ~color loc =
   let (f,l,b,e) = Loc.get loc in
   if f <> !current_file then
     begin
+      source_view#source_buffer#set_language (any_lang f);
       source_view#source_buffer#set_text (source_text f);
       set_current_file f;
     end;