diff --git a/scripts/pnglibconf.dfa b/scripts/pnglibconf.dfa
index bb22fb1e7..152eeaab2 100644
--- a/scripts/pnglibconf.dfa
+++ b/scripts/pnglibconf.dfa
@@ -8,7 +8,7 @@ com pnglibconf.h - library build configuration
 com
 version
 com
-com Copyright (c) 1998-2012 Glenn Randers-Pehrson
+com Copyright (c) 1998-2014 Glenn Randers-Pehrson
 com
 com This code is released under the libpng license.
 com For conditions of distribution and use, see the disclaimer
@@ -114,6 +114,13 @@ file pnglibconf.h scripts/pnglibconf.dfa PNGLCONF_H
 
 logunsupported = 1
 
+# The following allows the output from configure to modify the contents of
+# pnglibconf.h
+
+@#ifdef HAVE_CONFIG_H
+@#  include "config.h"
+@#endif
+
 # PNG_USER_CONFIG has to be defined on the compiler command line
 # to cause pngusr.h to be read while constructing pnglibconf.h
 #
@@ -189,10 +196,6 @@ setting API_RULE default 0
 
 setting PREFIX
 
-# Default to using the read macros
-
-setting DEFAULT_READ_MACROS default 1
-
 # Implementation specific control of the optimizations, enabled by those
 # hardware or software options that need it (typically when run-time choices
 # must be made by the user)
@@ -227,19 +230,21 @@ option ARM_NEON_CHECK disabled requires ALIGNED_MEMORY,
    sets ARM_NEON_OPT 1
 
 # These settings configure the default compression level (0-9) and 'strategy';
-# strategy is as defined by the implementors of zlib, it describes the input
+# strategy is as defined by the implementors of zlib. It describes the input
 # data and modifies the zlib parameters in an attempt to optimize the balance
 # between search and huffman encoding in the zlib algorithms.  The defaults are
 # the zlib.h defaults - the apparently recursive definition does not arise
 # because the name of the setting is prefixed by PNG_
 #
 # The TEXT values are the defaults when writing compressed text (all forms)
-#
-# Include the zlib header too, so that the defaults below are known
+
+# Include the zlib header so that the defaults below are known
 @#  include <zlib.h>
 
 # The '@' here means to substitute the value when pnglibconf.h is built
 setting Z_DEFAULT_COMPRESSION default @Z_DEFAULT_COMPRESSION
+# TODO: why aren't these Z_RLE; zlib.h says that Z_RLE, specifically, is
+# appropriate for PNG images, maybe it doesn't exist in all versions?
 setting Z_DEFAULT_STRATEGY default @Z_FILTERED
 setting Z_DEFAULT_NOFILTER_STRATEGY default @Z_DEFAULT_STRATEGY
 setting ZLIB_VERNUM default @ZLIB_VERNUM
@@ -247,6 +252,10 @@ setting ZLIB_VERNUM default @ZLIB_VERNUM
 setting TEXT_Z_DEFAULT_COMPRESSION default @Z_DEFAULT_COMPRESSION
 setting TEXT_Z_DEFAULT_STRATEGY default @Z_DEFAULT_STRATEGY
 
+# Default to using the read macros
+
+setting DEFAULT_READ_MACROS default 1
+
 # The alternative is to call functions to read PNG values, if
 # the functions are turned *off* the read macros must always
 # be enabled, so turning this off will actually force the
@@ -370,7 +379,16 @@ option SET_USER_LIMITS enables SET_CHUNK_MALLOC_LIMIT
 #
 # If these settings are *not* set libpng will not limit the size of
 # images or the size of data in ancilliary chunks.  This does lead to
-# security issues if PNG files come from untrusted sources.
+# security issues if PNG files come from untrusted sources.  Settings have the
+# following interpretations:
+#
+# USER_WIDTH_MAX: maximum width of an image that will be read
+# USER_HEIGHT_MAX: maximum height
+# USER_CHUNK_MALLOC_MAX: maximum in-memory (decompressed) size of a single chunk
+# USER_CHUNK_CACHE_MAX: maximum number of chunks to be cached
+#
+# Only chunks that are variable in number are counted towards the
+# USER_CHUNK_CACHE_MAX limit
 setting USER_WIDTH_MAX
 setting USER_HEIGHT_MAX
 setting USER_CHUNK_CACHE_MAX