DrawFrontend

 Author: Kurt Pagani 
 Date Created: 13 October 2016
 Date Revised: 13 April 2021
 Basic Operations:

GraphImage

 Author: Jim Wen
 Date Created: 27 April 1989
 Basic Operations:
 Related Constructors:
 Also See:
 AMS Classifications:
 Keywords:
 References:
 Description: TwoDimensionalGraph creates virtual two dimensional graphs
 (to be displayed on TwoDimensionalViewports).

 graphImage() returns an empty graph with 0 point lists
 of the domain \spadtype{GraphImage}.  A graph image contains
 the graph data component of a two dimensional viewport.

 sendGraphImage(gi) takes the given graph, \spad{gi} of the
 domain \spadtype{GraphImage}, and sends it's data to the
 viewport manager where it waits to be included in a two-dimensional
 viewport window.  \spad{gi} cannot be an empty graph.

 makeGraphImage(llp) returns a graph of the domain
 \spadtype{GraphImage} which is composed of the points and
 lines from the list of lists of points, \spad{llp}, with
 default point size and default point and line colours.

 makeGraphImage(llp, lpal1, lpal2, lp) returns a graph of the
 domain \spadtype{GraphImage} which is composed of the points
 and lines from the list of lists of points, \spad{llp}, whose
 point colors are indicated by the list of palette colors,
 \spad{lpal1}, and whose lines are colored according to the list
 of palette colors, \spad{lpal2}.  The paramater lp is a list of
 integers which denote the size of the data points.

 makeGraphImage(llp, lpal1, lpal2, lp, lopt) returns a graph of
 the domain \spadtype{GraphImage} which is composed of the
 points and lines from the list of lists of points, \spad{llp},
 whose point colors are indicated by the list of palette colors,
 \spad{lpal1}, and whose lines are colored according to the list
 of palette colors, \spad{lpal2}.  The paramater lp is a list of
 integers which denote the size of the data points, and \spad{lopt}
 is the list of draw command options.

 pointLists(gi) returns the list of lists of points which compose
 the given graph, \spad{gi}, of the domain \spadtype{GraphImage}.

 key(gi) returns the process ID of the given graph, \spad{gi},
 of the domain \spadtype{GraphImage}.

 ranges(gi) returns the list of ranges of the point components from
 the indicated graph, \spad{gi}, of the domain \spadtype{GraphImage}.

 ranges(gi, lr) modifies the list of ranges for the given graph,
 \spad{gi} of the domain \spadtype{GraphImage}, to be that of the
 list of range segments, \spad{lr}, and returns the new range list
 for \spad{gi}.

 units(gi) returns the list of unit increments for the x and y
 axes of the indicated graph, \spad{gi}, of the domain
 \spadtype{GraphImage}.

 units(gi, lu) modifies the list of unit increments for the x and y
 axes of the given graph, \spad{gi} of the domain
 \spadtype{GraphImage}, to be that of the list of unit increments,
 \spad{lu}, and returns the new list of units for \spad{gi}.

 component(gi, lp, pal1, pal2, p) sets the components of the
 graph, \spad{gi} of the domain \spadtype{GraphImage}, to the
 values given.  The point list for \spad{gi} is set to the list
 \spad{lp}, the color of the points in \spad{lp} is set to
 the palette color \spad{pal1}, the color of the lines which
 connect the points \spad{lp} is set to the palette color
 \spad{pal2}, and the size of the points in \spad{lp} is given
 by the integer p.

 component(gi, pt) modifies the graph \spad{gi} of the domain
 \spadtype{GraphImage} to contain one point component, \spad{pt}
 whose point color, line color and point size are determined by
 the default functions \spadfun{pointColorDefault},
 \spadfun{lineColorDefault}, and \spadfun{pointSizeDefault}.

 component(gi, pt, pal1, pal2, ps) modifies the graph \spad{gi} of
 the domain \spadtype{GraphImage} to contain one point component,
 \spad{pt} whose point color is set to the palette color \spad{pal1},
 line color is set to the palette color \spad{pal2}, and point
 size is set to the positive integer \spad{ps}.

 appendPoint(gi, pt) appends the point \spad{pt} to the end
 of the list of points component for the graph, \spad{gi}, which is
 of the domain \spadtype{GraphImage}.

 point(gi, pt, pal) modifies the graph \spad{gi} of the domain
 \spadtype{GraphImage} to contain one point component, \spad{pt}
 whose point color is set to be the palette color \spad{pal}, and
 whose line color and point size are determined by the default
 functions \spadfun{lineColorDefault} and \spadfun{pointSizeDefault}.

 coerce(llp) creates and returns a graph of the domain
 \spadtype{GraphImage} which is composed of the list of list
 of points given by \spad{llp}, and whose point colors, line colors
 and point sizes are determined by the default functions
 \spadfun{pointColorDefault}, \spadfun{lineColorDefault}, and
 \spadfun{pointSizeDefault}.  The graph data is then sent to the
 viewport manager where it waits to be included in a two-dimensional
 viewport window.

 coerce(gi) returns the indicated graph, \spad{gi}, of domain
 \spadtype{GraphImage} as output of the domain \spadtype{OutputForm}.

 putColorInfo(llp, lpal) takes a list of list of points, \spad{llp},
 and returns the points with their hue and shade components
 set according to the list of palette colors, \spad{lpal}.

TwoDimensionalViewport

 Author: Jim Wen
 Date Created: 28 April 1989
 Basic Operations:
 Related Constructors:
 Also See:
 AMS Classifications:
 Keywords:
 References:
 Description: TwoDimensionalViewport creates viewports to display graphs.

 getPickedPoints(x)
 returns a list of small floats for the points the
 user interactively picked on the viewport
 for full integration into the system, some design
 issues need to be addressed: e.g. how to go through
 the GraphImage interface, how to default to graphs, etc.

 viewport2D() returns an undefined two-dimensional viewport
 of the domain \spadtype{TwoDimensionalViewport} whose
 contents are empty.

 makeViewport2D(v) takes the given two-dimensional viewport,
 v, of the domain \spadtype{TwoDimensionalViewport} and
 displays a viewport window on the screen which contains
 the contents of v.

 options(v) takes the given two-dimensional viewport, v, of the
 domain \spadtype{TwoDimensionalViewport} and returns a list
 containing the draw options from the domain \spadtype{DrawOption}
 for v.

 options(v, lopt) takes the given two-dimensional viewport, v,
 of the domain \spadtype{TwoDimensionalViewport} and returns
 v with it's draw options modified to be those which are indicated
 in the given list, \spad{lopt} of domain \spadtype{DrawOption}.

 makeViewport2D(gi, lopt) creates and displays a viewport window
 of the domain \spadtype{TwoDimensionalViewport} whose graph
 field is assigned to be the given graph, \spad{gi}, of domain
 \spadtype{GraphImage}, and whose options field is set to be
 the list of options, \spad{lopt} of domain \spadtype{DrawOption}.

 graphState(v, num, sX, sY, dX, dY, pts, lns, box, axes, axesC, un, unC, cP)
 sets the state of the characteristics for the graph indicated
 by \spad{num} in the given two-dimensional viewport v, of domain
 \spadtype{TwoDimensionalViewport}, to the values given as
 parameters.  The scaling of the graph in the x and y component
 directions is set to be \spad{sX} and \spad{sY}; the window
 translation in the x and y component directions is set to be
 \spad{dX} and \spad{dY}; The graph points, lines, bounding box,
 axes, or units will be shown in the viewport if their given
 parameters \spad{pts}, \spad{lns}, \spad{box}, \spad{axes} or
 \spad{un} are set to be \spad{1}, but will not be shown if they
 are set to \spad{0}.  The color of the axes and the color of the
 units are indicated by the palette colors \spad{axesC} and
 \spad{unC} respectively.  To display the control panel when
 the viewport window is displayed, set \spad{cP} to \spad{1},
 otherwise set it to \spad{0}.

 graphStates(v) returns and shows a listing of a record containing
 the current state of the characteristics of each of the ten graph
 records in the given two-dimensional viewport, v, which is of
 domain \spadtype{TwoDimensionalViewport}.

 graphs(v) returns a vector, or list, which is a union of all
 the graphs, of the domain \spadtype{GraphImage}, which are
 allocated for the two-dimensional viewport, v, of domain
 \spadtype{TwoDimensionalViewport}.  Those graphs which have
 no data are labeled "undefined", otherwise their contents
 are shown.

 title(v, s) changes the title which is shown in the two-dimensional
 viewport window, v of domain \spadtype{TwoDimensionalViewport}.

 putGraph(v, gi, n) sets the graph field indicated by n, of the
 indicated two-dimensional viewport, v, which is of domain
 \spadtype{TwoDimensionalViewport}, to be the graph, \spad{gi}
 of domain \spadtype{GraphImage}.  The contents of viewport, v,
 will contain \spad{gi} when the function \spadfun{makeViewport2D}
 is called to create the an updated viewport v.

 getGraph(v, n) returns the graph which is of the domain
 \spadtype{GraphImage} which is located in graph field n
 of the given two-dimensional viewport, v, which is of the
 domain \spadtype{TwoDimensionalViewport}.

 axes(v, n, s) displays the axes of the graph in field n of
 the given two-dimensional viewport, v, which is of domain
 \spadtype{TwoDimensionalViewport}, if s is "on", or does
 not display the axes if s is "off".

 axes(v, n, c) displays the axes of the graph in field n of
 the given two-dimensional viewport, v, which is of domain
 \spadtype{TwoDimensionalViewport}, with the axes color set to
 the given palette color c.

 units(v, n, s) displays the units of the graph in field n of
 the given two-dimensional viewport, v, which is of domain
 \spadtype{TwoDimensionalViewport}, if s is "on", or does
 not display the units if s is "off".

 units(v, n, c) displays the units of the graph in field n of
 the given two-dimensional viewport, v, which is of domain
 \spadtype{TwoDimensionalViewport}, with the units color set to
 the given palette color c.

 points(v, n, s) displays the points of the graph in field n of
 the given two-dimensional viewport, v, which is of domain
 \spadtype{TwoDimensionalViewport}, if s is "on", or does
 not display the points if s is "off".

 region(v, n, s) displays the bounding box of the graph in
 field n of the given two-dimensional viewport, v, which is
 of domain \spadtype{TwoDimensionalViewport}, if s is "on",
 or does not display the bounding box if s is "off".

 connect(v, n, s) displays the lines connecting the graph
 points in field n of the given two-dimensional viewport, v,
 which is of domain \spadtype{TwoDimensionalViewport}, if s
 is "on", or does not display the lines if s is "off".

 controlPanel(v, s) displays the control panel of the given
 two-dimensional viewport, v, which is of domain
 \spadtype{TwoDimensionalViewport}, if s is "on", or hides
 the control panel if s is "off".

 close(v) closes the viewport window of the given
 two-dimensional viewport, v, which is of domain
 \spadtype{TwoDimensionalViewport}, and terminates the
 corresponding process ID.

 dimensions(v, x, y, width, height) sets the position of the
 upper left-hand corner of the two-dimensional viewport, v,
 which is of domain \spadtype{TwoDimensionalViewport}, to
 the window coordinate x, y, and sets the dimensions of the
 window to that of \spad{width}, \spad{height}.  The new
 dimensions are not displayed until the function
 \spadfun{makeViewport2D} is executed again for v.

 scale(v, n, sx, sy) displays the graph in field n of the given
 two-dimensional viewport, v, which is of domain
 \spadtype{TwoDimensionalViewport}, scaled by the factor \spad{sx}
 in the x-coordinate direction and by the factor \spad{sy} in
 the y-coordinate direction.

 translate(v, n, dx, dy) displays the graph in field n of the given
 two-dimensional viewport, v, which is of domain
 \spadtype{TwoDimensionalViewport}, translated by \spad{dx} in
 the x-coordinate direction from the center of the viewport, and
 by \spad{dy} in the y-coordinate direction from the center.
 Setting \spad{dx} and \spad{dy} to \spad{0} places the center
 of the graph at the center of the viewport.

 show(v, n, s) displays the graph in field n of the given
 two-dimensional viewport, v, which is of domain
 \spadtype{TwoDimensionalViewport}, if s is "on", or does not
 display the graph if s is "off".

 move(v, x, y) displays the two-dimensional viewport, v, which
 is of domain \spadtype{TwoDimensionalViewport}, with the upper
 left-hand corner of the viewport window at the screen
 coordinate position x, y.

 update(v, gr, n) drops the graph \spad{gr} in slot \spad{n}
 of viewport \spad{v}. The graph gr must have been
 transmitted already and acquired an integer key.

 resize(v, w, h) displays the two-dimensional viewport, v, which
 is of domain \spadtype{TwoDimensionalViewport}, with a width
 of w and a height of h, keeping the upper left-hand corner
 position unchanged.

 write(v, s) takes the given two-dimensional viewport, v, which
 is of domain \spadtype{TwoDimensionalViewport}, and creates
 a directory indicated by s, which contains the graph data
 files for v.

 write(v, s, f) takes the given two-dimensional viewport, v, which
 is of domain \spadtype{TwoDimensionalViewport}, and creates
 a directory indicated by s, which contains the graph data
 files for v and an optional file type f.

 write(v, s, lf) takes the given two-dimensional viewport, v, which
 is of domain \spadtype{TwoDimensionalViewport}, and creates
 a directory indicated by s, which contains the graph data
 files for v and the optional file types indicated by the list lf.

 reset(v) sets the current state of the graph characteristics
 of the given two-dimensional viewport, v, which is of domain
 \spadtype{TwoDimensionalViewport}, back to their initial settings.

 key(v) returns the process ID number of the given two-dimensional
 viewport, v, which is of domain \spadtype{TwoDimensionalViewport}.

 coerce(v) returns the given two-dimensional viewport, v, which
 is of domain \spadtype{TwoDimensionalViewport} as output of
 the domain \spadtype{OutputForm}.

 Sets the frontend according to the values in the FET table.

 Gets the FET table of the current frontend.

 Makes the frontend according to the values in the FET table.

ThreeDimensionalViewport

 Author: Jim Wen
 Date Created: 28 April 1989
 Basic Operations:
 Related Constructors:
 Also See:
 AMS Classifications:
 Keywords:
 References:
 Description: ThreeDimensionalViewport creates viewports to display graphs

 viewThetaDefault() returns the current default longitudinal
 view angle in radians.

 viewThetaDefault(t) sets the current default longitudinal
 view angle in radians to the value t and returns t.

 viewPhiDefault() returns the current default latitudinal
 view angle in radians.

 viewPhiDefault(p) sets the current default latitudinal
 view angle in radians to the value p and returns p.

 viewZoomDefault() returns the current default graph scaling
 value.

 viewZoomDefault(s) sets the current default graph scaling
 value to s and returns s.

 viewDeltaXDefault() returns the current default horizontal
 offset from the center of the viewport window.

 viewDeltaXDefault(dx) sets the current default horizontal
 offset from the center of the viewport window to be \spad{dx}
 and returns \spad{dx}.

 viewDeltaYDefault() returns the current default vertical
 offset from the center of the viewport window.

 viewDeltaYDefault(dy) sets the current default vertical
 offset from the center of the viewport window to be \spad{dy}
 and returns \spad{dy}.

 viewport3D() returns an undefined three-dimensional viewport
 of the domain \spadtype{ThreeDimensionalViewport} whose
 contents are empty.

 makeViewport3D(v) takes the given three-dimensional viewport,
 v, of the domain \spadtype{ThreeDimensionalViewport} and
 displays a viewport window on the screen which contains
 the contents of v.

 makeViewport3D(sp, s) takes the given space, \spad{sp} which is
 of the domain \spadtype{ThreeSpace} and displays a viewport
 window on the screen which contains the contents of \spad{sp},
 and whose title is given by s.

 makeViewport3D(sp, lopt) takes the given space, \spad{sp} which is
 of the domain \spadtype{ThreeSpace} and displays a viewport
 window on the screen which contains the contents of \spad{sp},
 and whose draw options are indicated by the list \spad{lopt}, which
 is a list of options from the domain \spad{DrawOption}.

 subspace(v) returns the contents of the viewport v, which is
 of the domain \spadtype{ThreeDimensionalViewport}, as a subspace
 of the domain \spad{ThreeSpace}.

 subspace(v, sp) places the contents of the viewport v, which is
 of the domain \spadtype{ThreeDimensionalViewport}, in the subspace
 \spad{sp}, which is of the domain \spad{ThreeSpace}.

 modifyPointData(v, ind, pt) takes the viewport, v, which is of the
 domain \spadtype{ThreeDimensionalViewport}, and places the data
 point, \spad{pt} into the list of points database of v at the index
 location given by \spad{ind}.

 options(v) takes the viewport, v, which is of the domain
 \spadtype{ThreeDimensionalViewport} and returns a list of all
 the draw options from the domain \spad{DrawOption} which are
 being used by v.

 options(v, lopt) takes the viewport, v, which is of the domain
 \spadtype{ThreeDimensionalViewport} and sets the draw options
 being used by v to those indicated in the list, \spad{lopt},
 which is a list of options from the domain \spad{DrawOption}.

 move(v, x, y) displays the three-dimensional viewport, v, which
 is of domain \spadtype{ThreeDimensionalViewport}, with the upper
 left-hand corner of the viewport window at the screen
 coordinate position x, y.

 resize(v, w, h) displays the three-dimensional viewport, v, which
 is of domain \spadtype{ThreeDimensionalViewport}, with a width
 of w and a height of h, keeping the upper left-hand corner
 position unchanged.

 title(v, s) changes the title which is shown in the three-dimensional
 viewport window, v of domain \spadtype{ThreeDimensionalViewport}.

 dimensions(v, x, y, width, height) sets the position of the
 upper left-hand corner of the three-dimensional viewport, v,
 which is of domain \spadtype{ThreeDimensionalViewport}, to
 the window coordinate x, y, and sets the dimensions of the
 window to that of \spad{width}, \spad{height}.  The new
 dimensions are not displayed until the function
 \spadfun{makeViewport3D} is executed again for v.

 viewpoint(v, th, phi, s, dx, dy) sets the longitudinal view angle
 to \spad{th} radians, the latitudinal view angle to \spad{phi}
 radians, the scale factor to \spad{s}, the horizontal viewport
 offset to \spad{dx}, and the vertical viewport offset to \spad{dy}
 for the viewport v, which is of the domain
 \spadtype{ThreeDimensionalViewport}.  The new viewpoint position
 is not displayed until the function \spadfun{makeViewport3D} is
 executed again for v.

 viewpoint(v) returns the current viewpoint setting of the given
 viewport, v.  This function is useful in the situation where the
 user has created a viewport, proceeded to interact with it via
 the control panel and desires to save the values of the viewpoint
 as the default settings for another viewport to be created using
 the system.

 viewpoint(v, viewpt) sets the viewpoint for the viewport.  The
 viewport record consists of the latitudal and longitudal angles,
 the zoom factor, the X, Y, and Z scales, and the X and Y displacements.

 viewpoint(v, th, phi, s, dx, dy) sets the longitudinal view angle
 to \spad{th} degrees, the latitudinal view angle to \spad{phi}
 degrees, the scale factor to \spad{s}, the horizontal viewport
 offset to \spad{dx}, and the vertical viewport offset to \spad{dy}
 for the viewport v, which is of the domain
 \spadtype{ThreeDimensionalViewport}.  The new viewpoint position
 is not displayed until the function \spadfun{makeViewport3D} is
 executed again for v.

 viewpoint(v, th, phi) sets the longitudinal view angle to \spad{th}
 radians and the latitudinal view angle to \spad{phi} radians
 for the viewport v, which is of the domain
 \spadtype{ThreeDimensionalViewport}.  The new viewpoint position
 is not displayed until the function \spadfun{makeViewport3D} is
 executed again for v.

 viewpoint(v, rotx, roty, rotz) sets the rotation about the x-axis
 to be \spad{rotx} radians, sets the rotation about the y-axis
 to be \spad{roty} radians, and sets the rotation about the z-axis
 to be \spad{rotz} radians, for the viewport v, which is of the
 domain \spadtype{ThreeDimensionalViewport} and displays v with
 the new view position.

 controlPanel(v, s) displays the control panel of the given
 three-dimensional viewport, v, which is of domain
 \spadtype{ThreeDimensionalViewport}, if s is "on", or hides
 the control panel if s is "off".

 axes(v, s) displays the axes of the given three-dimensional
 viewport, v, which is of domain \spadtype{ThreeDimensionalViewport},
 if s is "on", or does not display the axes if s is "off".

 diagonals(v, s) displays the diagonals of the polygon outline
 showing a triangularized surface instead of a quadrilateral
 surface outline, for the given three-dimensional viewport v
 which is of domain \spadtype{ThreeDimensionalViewport}, if s is
 "on", or does not display the diagonals if s is "off".

 outlineRender(v, s) displays the polygon outline showing either
 triangularized surface or a quadrilateral surface outline depending
 on the whether the \spadfun{diagonals} function has been set, for
 the given three-dimensional viewport v which is of domain
 \spadtype{ThreeDimensionalViewport}, if s is "on", or does not
 display the polygon outline if s is "off".

 drawStyle(v, s) displays the surface for the given three-dimensional
 viewport v which is of domain \spadtype{ThreeDimensionalViewport}
 in the style of drawing indicated by s.  If s is not a valid
 drawing style the style is wireframe by default.  Possible
 styles are \spad{"shade"}, \spad{"solid"} or \spad{"opaque"},
 \spad{"smooth"}, and \spad{"wireMesh"}.

 rotate(v, th, phi) rotates the graph to the longitudinal view angle
 \spad{th} radians and the latitudinal view angle \spad{phi} radians
 for the viewport v, which is of the domain
 \spadtype{ThreeDimensionalViewport}.

 rotate(v, th, phi) rotates the graph to the longitudinal view angle
 \spad{th} degrees and the latitudinal view angle \spad{phi} degrees
 for the viewport v, which is of the domain
 \spadtype{ThreeDimensionalViewport}.  The new rotation position
 is not displayed until the function \spadfun{makeViewport3D} is
 executed again for v.

 zoom(v, s) sets the graph scaling factor to s, for the viewport v,
 which is of the domain \spadtype{ThreeDimensionalViewport}.

 zoom(v, sx, sy, sz) sets the graph scaling factors for the x-coordinate
 axis to \spad{sx}, the y-coordinate axis to \spad{sy} and the
 z-coordinate axis to \spad{sz} for the viewport v, which is of
 the domain \spadtype{ThreeDimensionalViewport}.

 translate(v, dx, dy) sets the horizontal viewport offset to \spad{dx}
 and the vertical viewport offset to \spad{dy}, for the viewport v,
 which is of the domain \spadtype{ThreeDimensionalViewport}.

 perspective(v,s) displays the graph in perspective if s is "on",
 or does not display perspective if s is "off" for the given
 three-dimensional viewport, v, which is of domain
 \spadtype{ThreeDimensionalViewport}.

 eyeDistance(v, d) sets the distance of the observer from the center
 of the graph to d, for the viewport v, which is of the domain
 \spadtype{ThreeDimensionalViewport}.

 hitherPlane(v, h) sets the hither clipping plane of the graph to h,
 for the viewport v, which is of the domain
 \spadtype{ThreeDimensionalViewport}.

 showRegion(v, s) displays the bounding box of the given
 three-dimensional viewport, v, which is of domain
 \spadtype{ThreeDimensionalViewport}, if s is "on", or does not
 display the box if s is "off".

 showClipRegion(v, s) displays the clipping region of the given
 three-dimensional viewport, v, which is of domain
 \spadtype{ThreeDimensionalViewport}, if s is "on", or does not
 display the region if s is "off".

 clipSurface(v, s) displays the graph with the specified
 clipping region removed if s is "on", or displays the graph
 without clipping implemented if s is "off", for the given
 three-dimensional viewport, v, which is of domain
 \spadtype{ThreeDimensionalViewport}.

 lighting(v, x, y, z) sets the position of the light source to
 the coordinates x, y, and z and displays the graph for the given
 three-dimensional viewport, v, which is of domain
 \spadtype{ThreeDimensionalViewport}.

 intensity(v, i) sets the intensity of the light source to i, for
 the given three-dimensional viewport, v, which is of domain
 \spadtype{ThreeDimensionalViewport}.

 reset(v) sets the current state of the graph characteristics
 of the given three-dimensional viewport, v, which is of domain
 \spadtype{ThreeDimensionalViewport}, back to their initial settings.

 colorDef(v, c1, c2) sets the range of colors along the colormap so
 that the lower end of the colormap is defined by \spad{c1} and the
 top end of the colormap is defined by \spad{c2}, for the given
 three-dimensional viewport, v, which is of domain
 \spadtype{ThreeDimensionalViewport}.

 write(v, s) takes the given three-dimensional viewport, v, which
 is of domain \spadtype{ThreeDimensionalViewport}, and creates
 a directory indicated by s, which contains the graph data
 file for v.

 write(v, s, f) takes the given three-dimensional viewport, v, which
 is of domain \spadtype{ThreeDimensionalViewport}, and creates
 a directory indicated by s, which contains the graph data
 file for v and an optional file type f.

 write(v, s, lf) takes the given three-dimensional viewport, v, which
 is of domain \spadtype{ThreeDimensionalViewport}, and creates
 a directory indicated by s, which contains the graph data
 file for v and the optional file types indicated by the list lf.

 close(v) closes the viewport window of the given
 three-dimensional viewport, v, which is of domain
 \spadtype{ThreeDimensionalViewport}, and terminates the
 corresponding process ID.

 key(v) returns the process ID number of the given three-dimensional
 viewport, v, which is of domain \spadtype{ThreeDimensionalViewport}.

 Sets the frontend according to the values in the FET table.

 Gets the FET table of the current frontend.

 Make frontend according to the values in the FET table.