Add documentation to the zlib compression levels.

Enumerations are not listed by doxygen unless they have documentation
strings, so add them.

diff --git a/include/deal.II/base/data_out_base.h b/include/deal.II/base/data_out_base.h
index 813f51d1d0e463bfd1be8ab42fc58b9fc41adcc5..f2f6476a299803be06baee2fde905049594596a5 100644 (file)
--- a/include/deal.II/base/data_out_base.h
+++ b/include/deal.II/base/data_out_base.h
@@ -947,13 +947,28 @@ namespace DataOutBase
     bool print_date_and_time;
 
     /**
-     * A data type providing the different possible zlib compression levels.
+     * A data type providing the different possible zlib compression
+     * levels. These map directly to constants defined by zlib.
      */
     enum ZlibCompressionLevel
     {
+      /**
+       * Do not use any compression.
+       */
       no_compression,
+      /**
+       * Use the fastest available compression algorithm.
+       */
       best_speed,
+      /**
+       * Use the algorithm which results in the smallest compressed
+       * files. This is the default flag.
+       */
       best_compression,
+      /**
+       * Use the default compression algorithm. This is a compromise between
+       * speed and file size.
+       */
       default_compression
     };