[gnome-shell/gnome-3-6] shell-screen-grabber.c: Fix PBO path for big-endian machines

[Adel Gadllah <agadllah src gnome org>]

commit 980c3290de95d02a10e11c009920a7cbf20f313c
Author: Owen W. Taylor <otaylor fishsoup net>
Date:   Thu Oct 11 14:11:00 2012 -0400

    shell-screen-grabber.c: Fix PBO path for big-endian machines
    
    GL_BGRA/GL_UNSIGNED_BYTE only properly represents the Cairo pixel
    format for little-endian machines. On big endian machines we need to use
    GL_BGRA/GL_UNSIGNED_INT_8_8_8_8_REV. That would also work for little-
    endian, but for minimum disruption we keep using the old version on
    little endian.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=685915

 src/shell-screen-grabber.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)
---
diff --git a/src/shell-screen-grabber.c b/src/shell-screen-grabber.c
index 74caa89..c19bbdd 100644
--- a/src/shell-screen-grabber.c
+++ b/src/shell-screen-grabber.c
@@ -170,7 +170,16 @@ shell_screen_grabber_grab (ShellScreenGrabber *grabber,
        * top-left */
       glGetIntegerv (GL_VIEWPORT, vp_size);
       y = vp_size[3] - (y + height);
+
+      /* the "big-endian" version actually works for both, but the litle-endian
+       * version has been better tested with a range of drivers, so we'll
+       * keep on using it on little-endian.
+       */
+#if G_BYTE_ORDER == G_LITTLE_ENDIAN
       glReadPixels (x, y, width, height, GL_BGRA, GL_UNSIGNED_BYTE, 0);
+#else
+      glReadPixels (x, y, width, height, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, 0);
+#endif
 
       mapped_data = pf_glMapBufferARB (GL_PIXEL_PACK_BUFFER_ARB, GL_READ_ONLY_ARB);