\subsection{Creating Vertices and Edges}\index{Vertices!Creation}
\index{Edges!Creation}
Graphs can also be created using the mouse.  Clicking the $<3rd>$ button
on the canvas creates vertices, and clicking the same button on two vertices
in sequence creates the appropriate edge.  If the graph is a variety of
hypergraph, then edges containing more than two vertices.  This is 
accomplished by clicking $<3rd>$ on the first vertex of the edge, 
$<Shift-3rd>$ on all intermediate vertices, and finally clicking $<3rd>$
on the last vertex.

\subsection{Moving Vertices and Edges}
\index{Vertices!Moving}
\index{Edges!Moving}

The $<2nd>$ button is used to move vertices and edges around.  To move
an edge, make sure that the edge label is visible.  This label is also
the control point of a cubic spline, so that when you drag it around,
the edge is pulled into an arc.  This is necessary for visualizing
multigraphs, and generally useful for improving the appearance of 
drawings.

\subsection{Selecting Vertices and Edges}
\index{Vertices!Selecting}
\index{Edges!Selecting}

Vertices and edges are selected with the $<1st>$ button, and their 
appearance changes upon selection.  It is possible to select all of
the objects in a rectangular region by clicking $<1st>$ in an open
area of the canvas, then dragging the mouse while holding the button.
It is also possible to add to the selection with $<Shift-1st>$.  
SHIFT-1ST SHOULD BE A TOGGLE OPERATION, BUT IT IS NOT YET.  NEEDS TO
BE FIXED.

\subsection{Deleting Vertices and Edges}
\index{Vertices!Deleting}
\index{Edges!Deleting}

In order to delete a set of objects, simply select them and then select
the {\em Delete} option from the {\em Edit} menu.  An alternative to
pulling down the method is simply to type the character ``x'' on the
keyboard.

\subsection{Changing Attributes}
\index{Attributes!Changing from GUI}

The {\em Attributes} menu on the graph menubar allows the GUI user to 
modify the attributes of the graph.  It will be an easy change to allow
the user to choose which attribute is displayed as the vertex or edge
label, but this is not done as of 7/19/96.  However, it is straightforward
to modify the label, color, size, and/or width of vertices using the
options of this menu.
%	-color \\
%	-width \\
%	-size \\
%	-text-color \\
%	-label \\
%	-font \\
%	-weight \\
%	-world-coords \\
%	-x \\
%	-y \\
