From: Tim Waugh <twaugh@redhat.com>
Date: Thu, 16 Oct 2014 13:53:17 +0000 (+0100)
Subject: Don't use MIT-SHM on remote displays.
X-Git-Tag: v1.3.90~21^2~1
X-Git-Url: https://source.dussan.org/?a=commitdiff_plain;h=b17c9c4dedf09873b10b3c23d5f189aa9eba6978;p=tigervnc.git

Don't use MIT-SHM on remote displays.

When run from within 'ssh -X' or 'ssh -Y', MIT-SHM will appear to be
available even though it won't work: the shared memory will be on the
machine running vncviewer, not on the machine running the X server it
displays to. Depending on what shm segments are available on the
machine running the X server, the failure may not be apparent when
checking that MIT-SHM works.

Avoid this by not using MIT-SHM when XDisplayName() indicates we may
not be running locally.

Original bug report:
  https://bugzilla.redhat.com/show_bug.cgi?id=1072733
---

diff --git a/vncviewer/X11PixelBuffer.cxx b/vncviewer/X11PixelBuffer.cxx
index 59b90e2c..f83aa5f4 100644
--- a/vncviewer/X11PixelBuffer.cxx
+++ b/vncviewer/X11PixelBuffer.cxx
@@ -156,6 +156,11 @@ int X11PixelBuffer::setupShm()
   Bool pixmaps;
   XErrorHandler old_handler;
   Status status;
+  const char *display_name = XDisplayName (NULL);
+
+  /* Don't use MIT-SHM on remote displays */
+  if (*display_name && *display_name != ':')
+    return 0;
 
   if (!XShmQueryVersion(fl_display, &major, &minor, &pixmaps))
     return 0;