procedure
                        :checkbox               name

Creates a checkbox widget within the current panel frame for the TCL
interpreter. A checkbox widget is a frame window containing a label window
and a checkbutton window.
name is used to generate the path name of the windows to be created. It
should have the format of a widget name  (e.g.  :checkbox   CHK) and should
be unique within this interpreter. The name will be lower-cased (using the
string tolower command) in order to generate the path name used to create
the windows.
When the checkbox is selected using the mouse then the TCL command
click  FRAME “ ” CHECKBOX value
will be executed where FRAME and CHECKBOX are widget names and
value is the current state (0,1); (off,on) of the checkbox.
The path names generated have the root framename.panelname.checkbox-
name and the items label and button.
The :checkbox procedure may also be used directly within a frame window (i.e. before any
panel window has been created).


The :checkbox procedure may have a number of arguments however none
of these is mandatory.

        arguments
                        :x                      number
        number is the x-co-ordinate within the current panel of the checkbox
widget in pixels
        e.g.    :x 400

                        :y                      number
        number is the y-co-ordinate within the current panel of the checkbox
widget in pixels
        e.g.    :y 200
The :x and :y parameters may be omitted in which case the packer geometry manager will be
used and the position of the window will be determined by the contents of the master (panel)
window. If however the :x and :y parameters are supplied then the placer geometry manager
will be used to position the window within the master (panel) window.
Warning:        Note that it is not possible to mix use of the packer and placer geometry
managers within the same window. Thus all windows within a panel must request or imply that
the same geometry manager is used.

                        :value                  value
        value is the initial state of the checkbox (0/off; 1/on).
The default value is 0/off.


                        :valuex         value
        value is the position of the left hand edge of the checkbutton window
with relation to the left hand edge of the checkbox widget. It is thus the space
available to write the label string but also allows alignment of the checkbutton
windows of several checkbox widgets. The value may be expressed in units
of pixels or characters.
        e.g.    :valuex 100    (pixels);        :valuex 15c    (characters)

                        :label                  string
        string is a text string to be written into the label component of the
checkbox widget.
The default is the name of the checkbox widget.

                        :w                      value
        value is the width of the checkbutton in pixels.
By default the size of the checkbutton is determined by the image written into it.

                        :h                      value
        value is the height of the checkbutton in pixels.
By default the size of the checkbutton is determined by the image written into it.

                        :colours                list
        list may consist of one or two items which should be any valid colour
specification.  The first item defines the background colour for the checkbox
window and the second item defines the colour when the window is selected.
These colours override any colour selection made using the :colour
command or any user colour selection.
If the list contains only one item then only the background colour is defined and the normal
method is used to define the colour of the window when selected.


See also common procedure arguments defined later in this document.