print an error message if graphviz is not found

diff --git a/helm/software/matita/matitaMathView.ml b/helm/software/matita/matitaMathView.ml
index 63cf77a16e356352294078aa27e5651e7213e54c..329e27e4f8c909251dac4187cd4a87be1ddc64bc 100644 (file)
--- a/helm/software/matita/matitaMathView.ml
+++ b/helm/software/matita/matitaMathView.ml
@@ -1102,15 +1102,21 @@ class cicBrowser_impl ~(history:MatitaTypes.mathViewer_entry MatitaMisc.history)
       Lazy.force load_easter_egg
 
     method private redraw_gviz ?center_on () =
-      let tmpfile, oc = Filename.open_temp_file "matita" ".dot" in
-      let fmt = Format.formatter_of_out_channel oc in
-      MetadataDeps.DepGraph.render fmt gviz_graph;
-      close_out oc;
-      gviz#load_graph_from_file ~gviz_cmd:"tred | dot" tmpfile;
-      (match center_on with
-      | None -> ()
-      | Some uri -> gviz#center_on_href (UriManager.string_of_uri uri));
-      HExtlib.safe_remove tmpfile
+      if Sys.command "which dot" = 0 then
+       let tmpfile, oc = Filename.open_temp_file "matita" ".dot" in
+       let fmt = Format.formatter_of_out_channel oc in
+       MetadataDeps.DepGraph.render fmt gviz_graph;
+       close_out oc;
+       gviz#load_graph_from_file ~gviz_cmd:"tred | dot" tmpfile;
+       (match center_on with
+       | None -> ()
+       | Some uri -> gviz#center_on_href (UriManager.string_of_uri uri));
+       HExtlib.safe_remove tmpfile
+      else
+       MatitaGtkMisc.report_error ~title:"graphviz error"
+        ~message:("Graphviz is not installed but is necessary to render "^
+         "the graph of dependencies amoung objects. Please install it.")
+        ~parent:win#toplevel ()
 
     method private dependencies direction uri () =
       let dbd = LibraryDb.instance () in