Name: Marker_Select - Define and allow Pick Selection of Markers

 Type: Mapper, Image viewer upstream control module

 Language:  K&R C

 Author:    Ian Curington, AVS/UNIRAS Ltd. UK

 Description:

 Allow marker pick identification and display 
 from an input marker list and the image viewer
 system. Takes as input an AVS field with
 a list of coordinates for markers, displays them
 over an image (map) in the image viewer, and
 reacts to mouse picks on these markers, sending
 the pick selection to the output port.
 Markers are defined by geometric polyline vector lists,
 not ROI pixel masks.

 The input marker field is allowed to be either fully
 specified, or abreviated, with only X, Y, and PID.
 If a full marker field is specified, then you can
 externally control position, shape, size, etc.
 Any marker field sent out on the output port can
 be read back in to the input field port. This way
 state save and restore are possible. New marker
 lists can be made using the "marker_pick" module.
 This module does not allow edition of position or shape,
 just allows query picking of pre-defined markers.

 Two integer output ports provide information on the picked
 marker, the index number and the type or PID tag
 associated with that marker. These ports only change when
 a valid pick is made, otherwise they have values of
 -1, and -1, indicating no valid pick selection has been made.

 Inputs:
   Input Image: Reference image, same as that sent for
                display in the image viewer, used
                for feedback path.
   Mouse Info:  Part of upstream pick feedback communication
                with the image viewer
   IV Struct:   Part of upstream communications with the image viewer.
   Poly_Marker: Input field,
                  for marker pick list definition.
                This field is 1D uniform integer N-vector.
                If N-vector is 3, then each marker is assumed to be
                at an X, Y position, in pixels, relative to the top
                left corner of the image. The third value is an
                arbitrary PID tag value, that is simply displayed
                and passed out on an integer output port when
                a marker is picked with the mouse.
                If the field N-vector size is greater than 3, then
                it is assumed to be a full marker spec as defined
                in "marker.h", usually 7. This can fully specifiy
                variable marker shape, size, position, and hidden
                stroke vector used in the shape creation.

 Outputs:
   Poly_Marker_Output:
                This contains a full marker list, as a mirror to
                to the input list. It is always full 7-vector,
                even if the input port is the 3-vector format.
                This list can contain one additional marker not
                specified on the input list - to show an "X" over
                the top of the picked marker for display feedback
                for a successful pick operation.
                This port can be saved to a file with the
                "write field" module, and later restored with
                "read_field" on the input port during a later session.

  IV Draw Struct:
                Part of the image viewer upstream communication
                system.

  Pick-Index:   Integer output port with the index value of the
                picked marker. If no pick is valid, this port = -1.
  Pick-PID:     Integer output port with any PID tag value associated
                at the input port for the picked marker. This
                can be used by other modules in the network to
                provide additional query or more detailed information
                or dynamic behavior resulting from the pick operation.

 Parameters:
  Set Pick Mode: A one-shot button that registers the pick operation
                mode with the image viewer, in the case that multiple
                modules are also requesting pick communication with the
                image viewer.

  Pick Status Text Block:
                This is a square read-only text block used to
                show annotation about the picked marker.

  Marker Size:
                An integer slider from 1 to 10 (default=2) that
                controls the relative size of the markers
                when the input port is in the short X, Y, PID mode.
                When the full marker list is presented at the input
                port, the size is specified per marker, so this
                slider has no effect.