libpng 1.6 is stricter in various ways, which can trip up the PNG loader as it
considers all warnings fatal.

Upstream-Status: Backport
Signed-off-by: Ross Burton <ross.burton@intel.com>


From 2dd2c826a5b367d32cf2d48ed69754795990c5db Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 16 Apr 2013 10:58:56 +0100
Subject: [PATCH] png: Avoid marking the surface as in error after a png
 warning

It turns out that libpng will continue to load an image after throwing a
warning, and that libpng16 now throws warnings for images that libpng15
and earlier loaded without error. As we were happily loading those
images into cairo surfaces before, we are therefore being overzealous
in throwing an error now - so just squelch the warning.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 src/cairo-png.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/cairo-png.c b/src/cairo-png.c
index e74a4a8..068617d 100644
--- a/src/cairo-png.c
+++ b/src/cairo-png.c
@@ -149,13 +149,13 @@ static void
 png_simple_warning_callback (png_structp png,
 	                     png_const_charp error_msg)
 {
-    cairo_status_t *error = png_get_error_ptr (png);
-
-    /* default to the most likely error */
-    if (*error == CAIRO_STATUS_SUCCESS)
-	*error = _cairo_error (CAIRO_STATUS_NO_MEMORY);
-
-    /* png does not expect to abort and will try to tidy up after a warning */
+    /* png does not expect to abort and will try to tidy up and continue
+     * loading the image after a warning. So we also want to return the
+     * (incorrect?) surface.
+     *
+     * We use our own warning callback to squelch any attempts by libpng
+     * to write to stderr as we may not be in control of that output.
+     */
 }
 
 
-- 
1.7.10.4

