[master] Enabled iTXt support by default.

    To ensure binary compatibility with
    previous versions, the "lang" and "lang_key" members will be assumed
    to be omitted from previous versions unless the current libpng
    version was built with PNG_iTXt_SUPPORTED (which is otherwise no
    longer necessary to gain iTXt support), as a signal that the user has
    been building previous versions with PNG_iTXt_SUPPORTED as well.

ANNOUNCE

@@ -92,6 +92,12 @@ version 1.2.41beta09 [November 1, 2009]
   Merged libpng-1.2.41.txt with libpng-1.4.0.txt where appropriate.
 
 version 1.2.41beta10 [November 1, 2009]
+  Enabled iTXt support by default. To ensure binary compatibility with
+    previous versions, the "lang" and "lang_key" members will be assumed
+    to be omitted from previous versions unless the current libpng
+    version was built with PNG_iTXt_SUPPORTED (which is otherwise no
+    longer necessary to gain iTXt support), as a signal that the user has
+    been building previous versions with PNG_iTXt_SUPPORTED as well.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 

CHANGES

@@ -2522,6 +2522,12 @@ version 1.2.41beta09 [November 1, 2009]
   Merged libpng-1.2.41.txt with libpng-1.4.0.txt where appropriate.
 
 version 1.2.41beta10 [November 1, 2009]
+  Enabled iTXt support by default. To ensure binary compatibility with
+    previous versions, the "lang" and "lang_key" members will be assumed
+    to be omitted from previous versions unless the current libpng
+    version was built with PNG_iTXt_SUPPORTED (which is otherwise no
+    longer necessary to gain iTXt support), as a signal that the user has
+    been building previous versions with PNG_iTXt_SUPPORTED as well.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

libpng-1.2.41beta10.txt

@@ -2950,6 +2950,13 @@ accomplish this, the functions png_create_read_struct_2(),
 png_create_write_struct_2(), png_set_mem_fn(), png_get_mem_ptr(),
 png_malloc_default(), and png_free_default() were added.
 
+Support for the iTXt chunk has been enabled by default as of
+version 1.2.41.  If you have been defining PNG_iTXt_SUPPORTED
+already, please continue to do so, as a signal to libpng that your
+previous versions also supported iTXt. If you have not been defining
+PNG_iTXt_SUPPORTED, please don't start now; it will be enabled for
+you by default.
+
 Support for certain MNG features was enabled.
 
 Support for numbered error messages was added.  However, we never got

pngconf.h

@@ -526,6 +526,18 @@
  * will be turned on by default in libpng-1.4.0.
  */
 
+/* If you have previously been defining PNG_iTXt_SUPPORTED, please
+ * continue to do so in libpng-1.2.41 and later, until you switch to
+ * libpng-1.4.0, even though it is not necessary now to gain iTXt support.
+ * Your PNG_iTXt_SUPPORTED definition will be interpreted in png_set_text()
+ * as a signal that you have defined it in your builds of previous libpng
+ * versions that did not support iTXt by default.
+ */
+#if !defined(PNG_iTXt_SUPPORTED) && !defined(PNG_READ_iTXt_SUPPORTED) && \
+    !defined(PNG_WRITE_iTXt_SUPPORTED)
+#  define PNG_iTXt_NOT_PREVIOUSLY_SUPPORTED
+#endif
+
 #if defined(PNG_1_0_X) || defined (PNG_1_2_X)
 #  ifndef PNG_iTXt_SUPPORTED
 #    ifndef PNG_NO_iTXt_SUPPORTED

pngset.c

@@ -653,6 +653,7 @@ png_set_text_2(png_structp png_ptr, png_infop info_ptr, png_textp text_ptr,
                int num_text)
 {
    int i;
+   int caller_no_itxt = 0;
 
    png_debug1(1, "in %s storage function", ((png_ptr == NULL ||
       png_ptr->chunk_name[0] == '\0') ?
@@ -661,6 +662,19 @@ png_set_text_2(png_structp png_ptr, png_infop info_ptr, png_textp text_ptr,
    if (png_ptr == NULL || info_ptr == NULL || num_text == 0)
       return(0);
 
+#ifdef PNG_iTXt_NOT_PREVIOUSLY_SUPPORTED
+   /* If an earlier version of the library was used to build the
+    * application, it might be using a png_textp structure that
+    * does not contain the lang or lang_key elements. If you build
+    * this library with PNG_iTXt_SUPPORTED explicitly defined,
+    * then we assume that your older library was also built with
+    * PNG_iTXt_SUPPORTED defined and the complete png_textp structure
+    * has existed all along and it's safe to access them.  See pngconf.h.
+    */
+   if (png_ptr->flags & PNG_FLAG_LIBRARY_MISMATCH)
+      caller_no_itxt = 1;
+#endif
+
    /* Make sure we have enough space in the "text" array in info_struct
     * to hold all of the incoming text_ptr objects.
     */
@@ -721,17 +735,28 @@ png_set_text_2(png_structp png_ptr, png_infop info_ptr, png_textp text_ptr,
 #ifdef PNG_iTXt_SUPPORTED
       {
          /* Set iTXt data */
-         if (text_ptr[i].lang != NULL)
-            lang_len = png_strlen(text_ptr[i].lang);
-         else
+
+         if (caller_no_itxt == 0)
+         {
+            if (text_ptr[i].lang != NULL)
+               lang_len = png_strlen(text_ptr[i].lang);
+            else
+               lang_len = 0;
+            if (text_ptr[i].lang_key != NULL)
+               lang_key_len = png_strlen(text_ptr[i].lang_key);
+            else
+               lang_key_len = 0;
+         }
+
+         else /* Caller does not support iTXt */
+         {
             lang_len = 0;
-         if (text_ptr[i].lang_key != NULL)
-            lang_key_len = png_strlen(text_ptr[i].lang_key);
-         else
             lang_key_len = 0;
+            png_warning(png_ptr,
+               "iTXt lang and lang_key not available from application");
+         }
       }
-
-#else
+#else /* PNG_iTXt_SUPPORTED */
       {
          png_warning(png_ptr, "iTXt chunk not supported.");
          continue;