From 0fce7e85a1c853216866ddf6a40725e7ce57fe93 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Mon, 23 Apr 2007 13:00:40 +0100
Subject: [PATCH] Do not print out libpng error messages to stderr.

We wish to avoid writing to file descriptors (and streams) that are
outside cairo's control. In this case, the messages are superfluous as
the errors are propagated via the cairo_status_t returns.
---
 src/cairo-png.c | 31 +++++++++++++++++++++++++------
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/src/cairo-png.c b/src/cairo-png.c
index 74226226c..442fec5ff 100644
--- a/src/cairo-png.c
+++ b/src/cairo-png.c
@@ -83,6 +83,24 @@ convert_data_to_bytes (png_structp png, png_row_infop row_info, png_bytep data)
     }
 }
 
+/* Use a couple of simple error callbacks that do not print anything to
+ * stderr and rely on the user to check for errors via the cairo_status_t
+ * return.
+ */
+static void
+png_simple_error_callback (png_structp png_save_ptr,
+	                   png_const_charp error_msg)
+{
+    longjmp (png_save_ptr->jmpbuf, CAIRO_STATUS_NO_MEMORY);
+}
+
+static void
+png_simple_warning_callback (png_structp png_save_ptr,
+	                     png_const_charp error_msg)
+{
+}
+
+
 static cairo_status_t
 write_png (cairo_surface_t	*surface,
 	   png_rw_ptr		write_func,
@@ -118,7 +136,9 @@ write_png (cairo_surface_t	*surface,
     for (i = 0; i < image->height; i++)
 	rows[i] = (png_byte *) image->data + i * image->stride;
 
-    png = png_create_write_struct (PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+    png = png_create_write_struct (PNG_LIBPNG_VER_STRING, NULL,
+	                           png_simple_error_callback,
+	                           png_simple_warning_callback);
     if (png == NULL) {
 	status = CAIRO_STATUS_NO_MEMORY;
 	goto BAIL2;
@@ -130,10 +150,9 @@ write_png (cairo_surface_t	*surface,
 	goto BAIL3;
     }
 
-    if (setjmp (png_jmpbuf (png))) {
-	status = CAIRO_STATUS_NO_MEMORY;
+    status = setjmp (png_jmpbuf (png));
+    if (status)
 	goto BAIL3;
-    }
 
     png_set_write_fn (png, closure, write_func, NULL);
 
@@ -350,8 +369,8 @@ read_png (png_rw_ptr	read_func,
     /* XXX: Perhaps we'll want some other error handlers? */
     png = png_create_read_struct (PNG_LIBPNG_VER_STRING,
                                   NULL,
-                                  NULL,
-                                  NULL);
+	                          png_simple_error_callback,
+	                          png_simple_warning_callback);
     if (png == NULL)
 	goto BAIL;