[gtk-vnc] gvncviewer.py: add a '-h' and '--help' switch

[Daniel P. Berrange <dberrange src gnome org>]

commit ec6c7fea87badd4f2c9ef8f992d8c60c1bf99272
Author: Dr. Matthias St. Pierre <matthias st pierre ncp-e com>
Date:   Fri Oct 23 00:44:44 2020 +0200

    gvncviewer.py: add a '-h' and '--help' switch
    
    Also postpone the time consuming loading of the Gtk libraries until
    the sys.argv has been checked.

 examples/gvncviewer.py | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)
---
diff --git a/examples/gvncviewer.py b/examples/gvncviewer.py
index b9cd47d..e202b14 100755
--- a/examples/gvncviewer.py
+++ b/examples/gvncviewer.py
@@ -20,12 +20,6 @@
 
 from __future__ import print_function
 
-import gi
-gi.require_version('Gtk', '3.0')
-gi.require_version('GtkVnc', '2.0')
-from gi.repository import Gtk
-from gi.repository import Gdk
-from gi.repository import GtkVnc
 import sys
 
 usage = """
@@ -38,10 +32,21 @@ it defaults to 0.
 Alternatively, a unix domain socket can be specified using unix:<path>.
 """
 
+if "-h" in sys.argv or "--help" in sys.argv:
+    print(usage)
+    sys.exit(0)
+
 if len(sys.argv) != 2 and len(sys.argv) != 3:
     print(usage)
     sys.exit(1)
 
+import gi
+gi.require_version('Gtk', '3.0')
+gi.require_version('GtkVnc', '2.0')
+from gi.repository import Gtk
+from gi.repository import Gdk
+from gi.repository import GtkVnc
+
 def set_title(vnc, window, grabbed):
     name = vnc.get_name()
     keys = vnc.get_grab_keys()