Better document the argument for -geometry
It's not common knowledge these days how X geometry is specified, and
even the man page X(7) is missing on many systems now.
diff --git a/vncviewer/vncviewer.man b/vncviewer/vncviewer.man
index 8762dfb..ebfe772 100644
--- a/vncviewer/vncviewer.man
+++ b/vncviewer/vncviewer.man
@@ -119,7 +119,11 @@
.
.TP
.B \-geometry \fIgeometry\fP
-Standard X position and sizing specification.
+Initial position of the main VNC viewer window. The format is
+.B \fIwidth\fPx\fIheight\fP+\fIxoffset\fP+\fIyoffset\fP
+, where `+' signs can be replaced with `\-' signs to specify offsets from the
+right and/or from the bottom of the screen. Offsets are optional and the
+window will be placed by the window manager by default.
.
.TP
.B \-listen \fI[port]\fP