[devel] Add comment in pngtest.c about setting zlib strategy for text

compression

pngrutil.c

 
 /* pngrutil.c - utilities to read a PNG file
  *
- * Last changed in libpng 1.5.2 [March 31, 2011]
+ * Last changed in libpng 1.5.3 [(PENDING RELEASE)]
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)

pngtest.c

 
 /* pngtest.c - a simple test program to test libpng
  *
- * Last changed in libpng 1.5.0 [January 6, 2011]
+ * Last changed in libpng 1.5.3 [(PENDING RELEASE)]
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -914,6 +914,10 @@ test_one_file(PNG_CONST char *inname, PNG_CONST char *outname)
 #endif
 
 #ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION
+   /* Normally one would use Z_DEFAULT_STRATEGY for text compression.
+    * This is here just to make pngtest replicate the results from libpng
+    * versions prior to 1.5.3, and to test this new API.
+    */
    png_set_text_compression_strategy(write_ptr, Z_FILTERED);
 #endif