src/Tools/Graphview/etc/options

--- a/src/Tools/Graphview/etc/options	Wed Nov 28 16:27:21 2018 +0100
+++ b/src/Tools/Graphview/etc/options	Wed Nov 28 16:33:45 2018 +0100
@@ -2,7 +2,7 @@
 
 section "Graphview"
 
-option graphview_font_family : string = "Helvetica"
+option graphview_font_family : string = "Isabelle DejaVu Sans"
   -- "base font family (notably for PDF)"
 
 option graphview_font_size : int = 12