From 62cd380b8bff78bdcecce7fe6e68cb7a39bb1b33 Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Fri, 24 Sep 2010 21:42:15 +0000
Subject: [PATCH] add big-endian BGRA (Cairo) pixel buffer to RGBA (GdkPixbuf)
 pixel buffer conversion - restores text to the editor canvas on big-endian
 machines

git-svn-id: svn://localhost/ardour2/branches/2.0-ongoing@7841 d708f5d6-7413-0410-9779-e7cbd77b26cf
---
 gtk2_ardour/utils.cc | 51 ++++++++++++++++++++++++++++++++------------
 1 file changed, 37 insertions(+), 14 deletions(-)

diff --git a/gtk2_ardour/utils.cc b/gtk2_ardour/utils.cc
index d59ae3bb93..3c58a27e60 100644
--- a/gtk2_ardour/utils.cc
+++ b/gtk2_ardour/utils.cc
@@ -861,6 +861,7 @@ convert_color_channel (guint8 src,
 	return alpha ? ((guint (src) << 8) - src) / alpha : 0;
 }
 
+
 void
 convert_bgra_to_rgba (guint8 const* src,
 		      guint8*       dst,
@@ -870,20 +871,42 @@ convert_bgra_to_rgba (guint8 const* src,
 	guint8 const* src_pixel = src;
 	guint8*       dst_pixel = dst;
 	
-	for (int y = 0; y < height; y++)
-		for (int x = 0; x < width; x++)
-		{
-			dst_pixel[0] = convert_color_channel (src_pixel[2],
-							      src_pixel[3]);
-			dst_pixel[1] = convert_color_channel (src_pixel[1],
-							      src_pixel[3]);
-			dst_pixel[2] = convert_color_channel (src_pixel[0],
-							      src_pixel[3]);
-			dst_pixel[3] = src_pixel[3];
-			
-			dst_pixel += 4;
-			src_pixel += 4;
-		}
+	for (int y = 0; y < height; y++) {
+	  for (int x = 0; x < width; x++) {
+#if G_BYTE_ORDER == G_LITTLE_ENDIAN
+	    /* Cairo [ B G R A ] is actually  [ B G R A ] in memory SOURCE
+	                                        0 1 2 3
+	       Pixbuf [ R G B A ] is actually [ R G B A ] in memory DEST
+	    */
+	    dst_pixel[0] = convert_color_channel (src_pixel[2],
+						  src_pixel[3]); // R [0] <= [ 2 ]
+	    dst_pixel[1] = convert_color_channel (src_pixel[1],
+						  src_pixel[3]); // G [1] <= [ 1 ]
+	    dst_pixel[2] = convert_color_channel (src_pixel[0],  
+						  src_pixel[3]); // B [2] <= [ 0 ]
+	    dst_pixel[3] = src_pixel[3]; // alpha
+	    
+#elif G_BYTE_ORDER == G_BIG_ENDIAN
+	    /* Cairo [ B G R A ] is actually  [ A R G B ] in memory SOURCE
+	                                        0 1 2 3
+	       Pixbuf [ R G B A ] is actually [ R G B A ] in memory DEST
+	    */
+	    dst_pixel[0] = convert_color_channel (src_pixel[1],
+						  src_pixel[0]); // R [0] <= [ 1 ]
+	    dst_pixel[1] = convert_color_channel (src_pixel[2],
+						  src_pixel[0]); // G [1] <= [ 2 ]
+	    dst_pixel[2] = convert_color_channel (src_pixel[3],
+						  src_pixel[0]); // B [2] <= [ 3 ]
+	    dst_pixel[3] = src_pixel[0]; // alpha
+	    
+#else
+#error ardour does not currently support PDP-endianess
+#endif			
+
+	    dst_pixel += 4;
+	    src_pixel += 4;
+	  }
+	}
 }
 
 Glib::RefPtr<Gdk::Pixbuf>