master f622034fa5: Never set opaque region without an alpha channel

[Po Lu]

branch: master
commit f622034fa565a50f9c210301aba2545b2521f356
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Never set opaque region without an alpha channel
    
    * src/xfns.c (x_set_alpha_background): Don't modify opaque
    region if the visual has no alpha channel.
---
 src/xfns.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/xfns.c b/src/xfns.c
index 849fa72f39..6226f4063a 100644
--- a/src/xfns.c
+++ b/src/xfns.c
@@ -746,6 +746,9 @@ x_set_alpha_background (struct frame *f, Lisp_Object arg, 
Lisp_Object oldval)
                                  f->alpha_background != 1.0);
 #endif
 
+  if (!FRAME_DISPLAY_INFO (f)->alpha_bits)
+    return;
+
   if (f->alpha_background != 1.0)
     {
       XChangeProperty (FRAME_X_DISPLAY (f),