tuned signature;

--- a/src/Pure/Thy/html.scala	Thu Jun 01 21:15:56 2017 +0200
+++ b/src/Pure/Thy/html.scala	Thu Jun 01 21:24:33 2017 +0200
@@ -225,14 +225,16 @@
 
   /* document directory */
 
+  def isabelle_css: Path = Path.explode("~~/etc/isabelle.css")
+
   def init_dir(dir: Path)
   {
     Isabelle_System.mkdirs(dir)
-    File.copy(Path.explode("~~/etc/isabelle.css"), dir)
+    File.copy(isabelle_css, dir)
   }
 
   def write_document(dir: Path, name: String, head: XML.Body, body: XML.Body,
-    css: String = "isabelle.css", hidden: Boolean = true)
+    css: String = isabelle_css.base.implode, hidden: Boolean = true)
   {
     init_dir(dir)
     File.write(dir + Path.basic(name), output_document(head, body, css = css, hidden = hidden))

--- a/src/Pure/Thy/present.scala	Thu Jun 01 21:15:56 2017 +0200
+++ b/src/Pure/Thy/present.scala	Thu Jun 01 21:24:33 2017 +0200
@@ -93,7 +93,7 @@
       File.copy(graph_file, session_graph.file)
       Isabelle_System.bash("chmod a+r " + File.bash_path(session_graph))
 
-      File.copy(Path.explode("~~/etc/isabelle.css"), session_prefix)
+      File.copy(HTML.isabelle_css, session_prefix)
 
       for (font <- Isabelle_System.fonts(html = true))
         File.copy(font, session_fonts)

--- a/src/Tools/VSCode/src/preview.scala	Thu Jun 01 21:15:56 2017 +0200
+++ b/src/Tools/VSCode/src/preview.scala	Thu Jun 01 21:24:33 2017 +0200
@@ -49,7 +49,7 @@
         List(
           HTML.chapter("Theory " + quote(model.node_name.theory_base_name)),
           HTML.source(Symbol.decode(snapshot.node.commands.iterator.map(_.source).mkString))),
-        css = Url.print_file(Path.explode("~~/etc/isabelle.css").file))
+        css = Url.print_file(HTML.isabelle_css.file))
     (label, content)
   }
 }