chore: Clean up the conditional compilation that targeted libpng-1.7

In commit 96bc902 we forked the new
branch for libpng-1.8, but we left some of the preprocessor conditions
targeted at libpng-1.7 unresolved. Some of those were resolved in the
subsequent commits.

In this commit we are cleaning up the remaining ones.

contrib/libtests/pngimage.c

@@ -1,7 +1,7 @@
 
 /* pngimage.c
  *
- * Copyright (c) 2021 Cosmin Truta
+ * Copyright (c) 2021-2024 Cosmin Truta
  * Copyright (c) 2015,2016 John Cunningham Bowler
  *
  * This code is released under the libpng license.
@@ -46,7 +46,7 @@
 #  define SKIP 0
 #endif
 
-//#if PNG_LIBPNG_VER < 10700
+#if PNG_LIBPNG_VER != 10700
    /* READ_PNG and WRITE_PNG were not defined, so: */
 #  ifdef PNG_INFO_IMAGE_SUPPORTED
 #     ifdef PNG_SEQUENTIAL_READ_SUPPORTED
@@ -56,7 +56,7 @@
 #        define PNG_WRITE_PNG_SUPPORTED
 #     endif /* WRITE */
 #  endif /* INFO_IMAGE */
-//#endif /* pre 1.7.0 */
+#endif
 
 #ifdef PNG_READ_PNG_SUPPORTED
 /* If a transform is valid on both read and write this implies that if the

contrib/libtests/pngstest.c

@@ -1,7 +1,7 @@
 
 /* pngstest.c
  *
- * Copyright (c) 2021 Cosmin Truta
+ * Copyright (c) 2021-2024 Cosmin Truta
  * Copyright (c) 2013-2017 John Cunningham Bowler
  *
  * This code is released under the libpng license.
@@ -360,10 +360,10 @@ print_opts(png_uint_32 opts)
       printf(" --sRGB-16bit");
    if (opts & NO_RESEED)
       printf(" --noreseed");
-//#if PNG_LIBPNG_VER < 10700 /* else on by default */
+#if PNG_LIBPNG_VER != 10700 /* else on by default */
    if (opts & GBG_ERROR)
       printf(" --fault-gbg-warning");
-//#endif
+#endif
 }
 
 #define FORMAT_NO_CHANGE 0x80000000 /* additional flag */

contrib/libtests/pngunknown.c

@@ -1,7 +1,7 @@
 
 /* pngunknown.c - test the read side unknown chunk handling
  *
- * Copyright (c) 2021 Cosmin Truta
+ * Copyright (c) 2021-2024 Cosmin Truta
  * Copyright (c) 2015,2017 Glenn Randers-Pehrson
  * Written by John Cunningham Bowler
  *
@@ -98,7 +98,7 @@ typedef png_byte *png_const_bytep;
 #  define png_const_structp png_structp
 #endif
 
-//#if PNG_LIBPNG_VER < 10700
+#if PNG_LIBPNG_VER != 10700
    /* Copied from libpng 1.7.0 png.h */
 #define PNG_u2(b1, b2) (((unsigned int)(b1) << 8) + (b2))
 
@@ -143,7 +143,7 @@ typedef png_byte *png_const_bytep;
 #define PNG_CHUNK_RESERVED(c)     (1 & ((c) >> 13))
 #define PNG_CHUNK_SAFE_TO_COPY(c) (1 & ((c) >>  5))
 
-//#endif /* PNG_LIBPNG_VER < 10700 */
+#endif
 
 #ifdef __cplusplus
 #  define this not_the_cpp_this

contrib/tools/pngcp.c

@@ -53,7 +53,7 @@
 #  include "../../png.h"
 #endif
 
-//#if PNG_LIBPNG_VER < 10700
+#if PNG_LIBPNG_VER != 10700
    /* READ_PNG and WRITE_PNG were not defined, so: */
 #  ifdef PNG_INFO_IMAGE_SUPPORTED
 #     ifdef PNG_SEQUENTIAL_READ_SUPPORTED
@@ -63,7 +63,7 @@
 #        define PNG_WRITE_PNG_SUPPORTED
 #     endif /* WRITE */
 #  endif /* INFO_IMAGE */
-//#endif /* pre 1.7.0 */
+#endif
 
 #if (defined(PNG_READ_PNG_SUPPORTED)) && (defined(PNG_WRITE_PNG_SUPPORTED))
 #include <stdarg.h>
@@ -400,11 +400,11 @@ struct display
    png_alloc_size_t read_size;
    png_structp      read_pp;
    png_infop        ip;
-//#  if PNG_LIBPNG_VER < 10700 && defined PNG_TEXT_SUPPORTED
+#  if PNG_LIBPNG_VER != 10700 && defined PNG_TEXT_SUPPORTED
       png_textp     text_ptr; /* stash of text chunks */
       int           num_text;
       int           text_stashed;
-//#  endif /* pre 1.7 */
+#  endif
 
 #  ifdef PNG_PNGCP_TIMING_SUPPORTED
       struct timespec   read_time;
@@ -489,11 +489,11 @@ display_init(struct display *dp)
    dp->ip = NULL;
    dp->write_pp = NULL;
    dp->min_windowBits = -1; /* this is an OPTIND, so -1 won't match anything */
-//#  if PNG_LIBPNG_VER < 10700 && defined PNG_TEXT_SUPPORTED
+#  if PNG_LIBPNG_VER != 10700 && defined PNG_TEXT_SUPPORTED
       dp->text_ptr = NULL;
       dp->num_text = 0;
       dp->text_stashed = 0;
-//#  endif /* pre 1.7 */
+#  endif
 }
 
 static void
@@ -531,7 +531,7 @@ display_clean(struct display *dp)
    display_clean_write(dp, 1/*freeinfo*/);
    dp->output_file = NULL;
 
-//#  if PNG_LIBPNG_VER < 10700 && defined PNG_TEXT_SUPPORTED
+#  if PNG_LIBPNG_VER != 10700 && defined PNG_TEXT_SUPPORTED
       /* This is actually created and used by the write code, but only
        * once; it has to be retained for subsequent writes of the same file.
        */
@@ -542,7 +542,7 @@ display_clean(struct display *dp)
          free(dp->text_ptr);
          dp->text_ptr = NULL;
       }
-//#  endif /* pre 1.7 */
+#  endif
 
    /* leave the filename for error detection */
    dp->results = 0; /* reset for next time */
@@ -635,7 +635,7 @@ display_log(struct display *dp, error_level level, const char *fmt, ...)
    }
 }
 
-//#if PNG_LIBPNG_VER < 10700 && defined PNG_TEXT_SUPPORTED
+#if PNG_LIBPNG_VER != 10700 && defined PNG_TEXT_SUPPORTED
 static void
 text_stash(struct display *dp)
 {
@@ -687,10 +687,10 @@ text_restore(struct display *dp)
 
 #define text_restore(dp) if (dp->text_stashed) text_restore(dp)
 
-//#else
-//#define text_stash(dp) ((void)0)
-//#define text_restore(dp) ((void)0)
-//#endif /* pre 1.7 */
+#else
+#define text_stash(dp) ((void)0)
+#define text_restore(dp) ((void)0)
+#endif
 
 /* OPTIONS:
  *

contrib/tools/pngfix.c

@@ -84,7 +84,7 @@
 #  define aligncastconst(type, value) ((const void*)(value))
 #endif /* __cplusplus */
 
-//#if PNG_LIBPNG_VER < 10700
+#if PNG_LIBPNG_VER != 10700
 /* Chunk tags (copied from pngpriv.h) */
 #define PNG_32b(b,s) ((png_uint_32)(b) << (s))
 #define PNG_U32(b1,b2,b3,b4) \
@@ -117,7 +117,7 @@
 #define png_tIME PNG_U32(116,  73,  77,  69)
 #define png_tRNS PNG_U32(116,  82,  78,  83)
 #define png_zTXt PNG_U32(122,  84,  88, 116)
-//#endif
+#endif
 
 /* The 8-byte signature as a pair of 32-bit quantities */
 #define sig1 PNG_U32(137,  80,  78,  71)