For plotutils version 2.x
-------------------------

libplot: add the display list concept (will facilitate adding support for
compound objects and much else).

libplot: support copying graphics from one Plotter to another (via display
list).

libsciplot: new library.  Incorporate all functionality of VOGLE, PGPLOT,
and PLPLOT libraries; check into GLE, PLOTPLUS, XYPLOT, DISLIN.  Think
about Guile, and Tcl/Tk, and Python.  libsciplot will support contouring,
but not 3d surface plots yet.

graph: librarify the plotting routines, and incorporate them in libsciplot.
N.B. need better clipping for filled regions (present gnuplot-style
clipping scheme is right for unfilled regions but wrong for filled ones)

libsciplot: when plotting a curve containing data points, symbols should be
plotted _last_, after endpath() is called.

plot: should document that `plot -TX' will use double buffering if
environment variable USE_DOUBLE_BUFFERING is "yes".  Maybe make that
user-settable via an option?

libplot: support object-level clipping

libplot: add support for compound objects

libplot: add support for tiling instead of solid filling

libplot: add support for subpaths i.e. compound paths.

graph: new option to put frame on top of plot, not vice versa.
maybe automatic, if `plotting is real time' capability is set?

libplot X drawable support: add parameter(s) for offset of canvas within
drawable?

graph: add legend support (need new --legend :string1:string2: option),
i.e. gnuplot-style `key'.  Maybe arbitrarily positioned arrows, text
strings also.  See how NCAR Graphics does it.

Internationalization: think about removing strcasecmp (what if user called
setlocale i.e. set LOCALE env var)?  Similarly worry about . vs , everywhere, 
e.g. in PS files.

graph: fix positioning of top labels, especially at large sizes

ode: add atan2() function

libplot: Support CGM format.  Check that CGM is importable into Corel Draw
as well as Illustrator.

libplot: add triangular cap mode, join mode to more types of Plotter

write more man pages.

Major Enhancements (Possible, Probable, or Certain)
---------------------------------------------------

libplot: support PGML output format, maybe VML.

ode: extend parser to plot functions as well as solve differential equations

libplot: redo X driver, to support window reuse (`persistence') by any
X Plotter.  Will require forking off an outboard process.

graph parsing: allow all command-line options in data files, on comment lines

graph: Write alternative parser for interactive version (gnuplot replacement).

libplot: add interactivity (e.g. getloc()), during openpl()...closepl().
Need to translate back to user coordinates.  [For libsciplot, even
further?]  For Tektronix driver, implement GIN mode (need stty twiddling?).
Also need char input (cf. starbase).

libplot: use freeware rasterizer for type 1 fonts [t1lib, by Rainer
Menzner; see
ftp://ftp.neuroinformatik.ruhr-uni-bochum.de/pub/software/t1lib ].

libplot: gradient fill?

Break out spline() as subroutine(s), cf. fitpack?  Cf. IMSL interface.
Similarly with plot frame / axis drawing.  For this, check into NCAR
Graphics package, `autograph' routines.

ode: need popen() for output; cf. gnuplot

graph: add `boxes', `steps', `impulses', `bars' plot types (as in gnuplot).
Boxes, bars should properly support --fill-fraction option.

graph: add support for polar/spherical plots, 3-D (surface) plotting

spline: add support for smoothing splines as well as interpolatory splines?

Other needed math software:

	fitting capability
	contour plotting via level curves; also compute enclosed area
	surface plotting	(cf. IDL for plotting and contouring)


Low-priority items (may be done someday)
----------------------------------------

libplot X driver: should use a non-default visual if the default visual
isn't read-only?

libplot X driver: solve the problem of zombie children.

libplot: spline the Hershey fonts, use new spline primitive to draw them.

Very old HP-GL pen plotters can't handle full range of coordinates in many
of our page types [see libplot/g_pagetype.h; our current page sizes, taken
from AutoCAD, may not be appropriate for very old pen plotters?]

Improve libplot error reporting: change libplot error handler to use name
of executable.

Add comment() function, takes printable string as arg (no control chars).

ode: need no stack blowout

Hershey fonts: 
1. add euro and cedilla
2. add support for Hershey indexical positioning on baseline?

graph, plot, tek2plot, plotfont, etc.: add --display and --geometry
options?

check into test/plot2tek.test (not currently run, seems to give
system-dependent behavior depending on rounding mode?)

libplot text string format: \mk..\rt etc. could be stack machine; should
also include overline, underline, radical, display fractions etc.  Cf. eqn
and Allen Hershey's typesetting.

libplot: polyline hatching as well as filling?

libplot: add support for rectangular raster objects ("device independent
rasters").
