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		GIST - A Scientific Graphics Package
			For UNIX Workstations

   $Id: README,v 1.1 2005-09-18 22:04:19 dhmunro Exp $


1) Three levels of graphics functions:
	 P (primitives), A (advanced), and D (display list)
   Routines are provided for creating and editing display list elements.
   When a display list is rendered, calls to the advanced and primitive
   graphics functions are generated.  `A' level functions call `P' level
	A few functions are provided at a fourth level, H (high level),
   which embodies the control functions described in the suggested
   interactive interface below.

2) The `P' level functions call virtual rendering functions for all
   active graphics `engines'.  Three types of engines are provided:

      X Window System engines- draw to an X Window.  If the `D' level
         Gist routines have been used to construct a display list, then
         a Gist X engine can redraw itself if it is damaged by X exposure

      PostScript engines- output to a PostScript file which can be sent
         to many printers directly.

      CGM engines- output to a binary CGM metafile to allow for archiving
         large numbers of graphics frames for which PostScript output
         is too disk-intensive.

   Additional types of engines can be added by supplying virtual functions
   for the six graphical primitives (DrawLines, DrawMarkers, DrawText,
   DrawFill, DrawCells, and DrawDisjoint), and a half dozen additional
   control functions to perform actions such as destroying the engine,
   changing coordinate transformations, advancing to a new page, etc.
   Input to the rendering functions is in floating point coordinates,
   with a coordinate transformation.  Gist supplies most of the functions
   you should need to convert these into device coordinates.  Input to
   the primitives has already been clipped to the current viewport.

   Care has been taken to assure that only those engines which your code
   actually uses will be linked.

3) The `D' and `A' level routines render the following types of objects:

     Decorated lines:  Open or closed polylines in several linestyles,
                       with any width or color, optionally including
                       overstruck occasional marker characters or
                       ray arrows.

     Quadrilateral meshes:  May have arbitrary logical holes (missing
                            zones), and you may optionally draw individual
                            regions or region boundaries (instead of the
                            full mesh).  In addition to mesh lines, there
                            are three other display list elements which
                            can be used to show information about
                            quadrilateral meshes:

        Contours:  Trace level curves.  Mesh triangulation may be specified.
        Vectors:  Filled or hollow vector arrows at each mesh point.
        Filled Mesh:  The color of each zone reflects the value of a
                      function-- an alternative to contour plots.

     Images:  Implemented as cell arrays, so the image cell size can be
              easily changed.

     Text:  Supports Courier, Times, Helvetica, Symbol, and New Century
            Schoolbook fonts on all devices (the X versions of these are
            supplied with the MIT R4 release).

     Axis ticks and labels:  Linear and logarithmic "rulers" appropriately
            labeled.  Ticks always at "nice" numbers (i.e.- numbers ending
            with 0, 1, 2, or 5) of labeled ticks and minor ticks adjustable.
            Tick lengths and number of tick levels in the ruler hierarchy
            adjustable.  Optional grid lines.  Axes can be drawn on any
            or all four sides of a plot, or at a "nice" intermediate
            position (to get x and y axes interior to the plot).  Provision
            for scales with extremely small fractional variation (and
            therefore extremely long tick labels).

4) Gist provides a browser, "gist", for its CGM metafiles (it is not
   sufficiently general to handle any other metafiles, but, like the rest
   of Gist, it is easy to port to any UNIX workstation).  The gist
   browser can output pages in arbitrary order to an X window, a
   PostScript file, another CGM file, or to an EPS file (for input to

Known problems:

General note:
The event-driven input dispatcher (dispat.c, dispas.c, dispax.c) is not
very well designed.  The files events.[ch], osmem.c, ospoll.c, osterm.c,
and ostime.c are a sketch of a better design; they are not currently
used, but I'm working on it...

   a) In Xlib.h, the style for declaring struct typedefs is an unhappy
      one.  In particular, the HPUX 8.05 ANSI C compiler on HP 700
      series machines issues a warning about the XImage data structure;
      the complaint is that the declaration in Xlib.h reads:
      typedef struct _XImage {
        (*VirtualFunction)(.., struct _XImage *, ..);
      } XImage;
      And when you pass this VirtualFunction an XImage*, the compiler
      complains that an XImage* pointer shouldn't be cast to a
      struct _XImage* pointer.  The correct thing to do is to get HP to
      fix either Xlib.h, or to teach their compiler about this
      programming style.

   b) The HPUX 8.05 <stdio.h>, when _HPUX_SOURCE is defined, declares
      and provides a prototype for the select function.  I therefore
      removed my prototype (it returns an int, so it can be implicitly
      declared).  However, there is a slight disagreement in argument
      types which produces a warning message.

   c) If you get a warning or error about the cuserid() function when
      osys.c compiles, change the definition of D_CUSERID in the
      Makefile and try again.

   c) If you get a warning or error about the exp10() function when
      the bench program loads, change the definition of D_HAS_EXP10
      in the Makefile and try again.

   e) A strict ANSI compiler will often produce reams of warnings from
      subsidiary files included by Xlib.h.  Obviously, this is not my
      problem.  If you have this problem, experiment with a simple code
      which includes <X11/Xlib.h>, <X11/Xutil.h>, and <X11/Xos.h>, until
      you have worked out a way to curb the warnings, or convinced
      yourself that the warnings are harmless.

Suggested interactive interface (control functions are partially
                                 implemented in hlevel.h, hlevel.c):

1) Plotting functions:

   plg, x, y
   plg, y	Plot graph, with keywords to add markers, ray arrows, etc.
     gistA.l=  ...linestyle...
     gistA.dl= ...decorations...
     gistA.m=  ...marker style...
     gistD.hide= 0
     gistD.legend= ...legend text...
     GdLines(n, x, y)

   plm, x, y, ireg
   plm, x, y
   plm		Plot mesh with optional zone region number array ireg
     gistA.l=  ...linestyle...
     gistA.mesh= ...(x, y, ireg)... (ireg can be NULL)
     gistD.hide= 0
     gistD.legend= ...legend text...
     GdMesh(region, boundary)

   plc, z, x, y, ireg
   plc, z	Plot contours of point-centered function z, with levs=
                keyword to specify levels
     gistA.l=  ...linestyle...
     gistA.dl= ...decorations...
     gistA.m=  ...marker style...
     gistD.hide= 0
     gistD.legend= ...legend text...
     GdContours(z, triangulation, levels, nLevels)

   plv, u, v, scale, x, y, ireg
   plv, u, v, scale	Plot vector arrows
     gistA.l=  ...linestyle (if hollow)...
     gistA.f=  ...fill style (if filled)...
     gistA.vect= ...vector style...
     gistD.hide= 0
     gistD.legend= ...legend text...
     GdVectors(u, v, scale)

   plf, colors, x, y, ireg
   plf, colors	Plot filled mesh
     gistD.hide= 0
     gistD.legend= ...legend text...

   pli, image, px, py, qx, qy
   pli, image	Plot image (cell array)
     gistD.hide= 0
     gistD.legend= ...legend text...
     GdCells(px, py, qx, qy, width, height, width, image)

   plt, text, x0, y0	Plot text with keywords for font, size, alignment
     gistD.hide= 0
     gistD.legend= 0
     gistA.t= ...text properties...
     GdSetDrawing(current_drawing)  /* saves current coordinate system */
     GdText(x0, y0, text)           /* (x0, y0) in NDC coordinates */
     GdSetDrawing(0)                /* restore original coordinates */

2) Coordinate systems:

   {xmin, xmax, ymin, ymax, flags}= lquery()
		Return the current limits and flags.  The actual values
		of the limits after extreme value calculation and other
		adjustments are returned.

   limits, xmin, ymin, xmax, ymax
   limits, {xmin, xmax, ymin, ymax, flags}  /* returned by lquery */
   limits, xmin, xmax
   range, ymin, ymax
		Set plot limits, can be numbers or "e" to get extreme
		values.  Takes keywords nice=1 (to force ends of axes
		to "nice" numbers), square=1 (to force dy=dx if any of
		the limits are set to extreme values), and restrict=1
		(to cause the extreme value search for x limits to
		ignore any points outside of fixed y limits and vice
     gistD.window= {xmin, xmax, ymin, ymax}
     gistD.flags= {extreme, nice, square, restrict}

   logxy, xFlag, yFlag
		Set or reset log axis scaling
     gistD.flags= {xIsLog, yIsLog}

   coordsys, systemNumber
		Set current coordinate system (for drawing styles with
                multiple coordinate systems on the page)

3) Plot editing:

   elementType= plquery(elementIndex, keywords=...)
   elementType= plquery(keywords=...)
		Get information about a display list element.  Keywords
                can be any keyword legal in any of plotting commands, or
                the name of any formal parameter name for those commands.
                One additional keyword, level=levelIndex, allows selection
                of individual contour levels.  Also takes default=1
		keyword to retrieve current default styles.
       maybe GdGetContour(levelIndex)

   pledit, elementIndex_list, keywords=...
   pledit, keywords=...
		Edit values for one or more elements.  Keywords are same
		as for plquery.  Some keywords do not make sense with
		more than one elementIndex.
     for (i=0 ; i<sizeof(elementIndex_list) ; i++)
         maybe GdGetContour(levelIndex)
       gistA.?= new value;  gistD.?= new value
       GdEdit(0 or 1)

4) Current window control functions:

		Before pausing for keyboard input, the following Gist
		sequence should be issued to assure that the current X
		display is up-to-date:

   fma		Frame advance.  Sends current drawing to all active
		devices.  Optionally activates hardcopy device.
		Optionally performs animation (see below).  If the
		animation mode is not set, the Gist calls are:

   redraw	erase and redraw current X display

   hcp		Send current X display to hardcopy file.  Takes optional
		file= keyword to create a new output file.

   hcpoff	Toggle whether fma activates/deactivates the
		hardcopy engine.  There is no way to permanently activate
		the hcp_engine interactively, avoiding problems with new
		frames appearing for every interactive resetting of limits
		or editing.  If no interactive pauses occur before the
		fma, then full efficiency is attained; otherwise the
		display list will be traversed once to send to the screen,
		and a second time to send to hardcopy, just as for the
		explicit hcp command.
     GhFMAMode(1 or 0, 2)

   animate, 0 or 1
   animate	Toggle animation mode for the current coordinate system.
		If all four limits are fixed, then only the viewport for
		the system is animated, otherwise the viewport and its
		ticks and labels are animated.  In this mode, the X engine
		draws to an offscreen pixmap which "blits" to the screen
		when the fma command is issued (see fma above).  Only one
		coordinate system can be animated at a time (since there
		usually IS only one, this is not much of a limitation).
		When animate mode is turned on, the decision of whether
		to animate the tick marks or just the viewport of the
		current system is made depending on whether all four
		limits are fixed.  When animation is turned on:
     GhFMAMode(2, 0 or 1)

   palette, r, g, b
   palette, ""
   palette, r, g, b, query=1
		Set current color palette either from explicit (r, g, b)
		arrays, or from a Gist palette file.  Takes ntsc=1
		keyword if grays for monochrome output devices are to
		be computed using NTSC TV standard rather than simple
		intensity.  Takes query=1 keyword to output to (r, g, b).
     GpSetPalette(x_display_engine, {r, g, b}, nColors)
       GpGetPalette(x_display_engine, {r, g, b})
       GpReadPalette(x_display_engine, "")

   pllist, elementIndex_list
   pllist	Prints list of legends at terminal.  Takes levels=1
		keyword to print individual level legends.  This is
		how you can determine the elementIndex for a given
		display list element.
     GdGetElement(elementIndex)    /* called in a loop */

5) Multiple window control functions:

   By default, you get one X window.  At the first use of the hcp command,
   a metafile will be created.  By default, this is a CGM file with a
   unique name, although both hcp and hcpon take a file= keyword to specify
   the filename.  By default, hardcopy files are CGM files whose filename
   will have ".cgm" appended (if not present).  You get a PostScript file
   by explicitly specifying a filename ending with ".ps".  You can close
   the existing file and not create a new one by specifying file="".

   If you want, you can switch to a second or third X window.  The plotting
   commands only deliver output to one X window at a time, but the other
   windows remain visible, and you can reinstate them whenever you want.
   Each X window has its own display list.  You can also have a display
   list which is not associated with any X window-- only a hardcopy file.
   Finally, each display list can have its own hardcopy file, which overrides
   the default hardcopy file shared among all display lists.

   All this is handled by two somewhat complicated functions:

   pldevice, number     /* 0<= number < 8 */
		Sets current display list to `number', if a display list
		with this number already exists, or creates a new display
		list with this number if there is none.  Takes keywords:
      display= "host:server.screen"
		Sets the display for X window.  Use "" to get no X window,
		since if this keyword is omitted you get a window on
		the display named by your DISPLAY environment variable.
      file= "hcp_file"
		Sets the name for the associated hardcopy file.  Use ""
		to revert to the default hcp file.  If you don't specify
		file= when creating a new display list, this is what you
		get by default.
      style= "standard_style"
		Name of style file to use for specifying layout of drawing.
		Default is "".  If you change this for an existing
		display list (X window), its current contents are erased
		as a side effect.
      hcplegends= 0 or 1
		Legends are not displayed in the X windows (use pllist);
		this switch controls whether legends are written to the
		hcp file.  Default is hcplegends=1.
      dpi= 75 or 100
		Resolution for the X window.  75 makes a small window; 100
		is the default.

   hcpdevice, file= "hcp_file"
		Sets the default hardcopy device used by any display lists
		which don't have their own hcp file as specified with
		pldevice.  Use file="" to close the current file.  If there
		is no default hcp file and an hcp command requires one,
		a default CGM file with a unique name will be created

   If no explicit pldevice command is issued, the first plotting command
   does an implicit "pldevice, 0", which brings up a local X window and
   makes it the current output device.  The first hcp command then triggers
   the creation of a hardcopy file as mentioned under the description
   of hcpdevice.  To preempt this sequence, you must call pldevice
   explicitly before plotting anything.  Use ` pldevice,0, display="" '
   to plot without creating any X windows.

6) Summary of interactive functions:
     Plotting:     plg, plm, plc, plv, plf, pli, plt
     Coordinates:  lquery, limits, range, logxy, coordsys
     Editing:      plquery, pledit
     Control:      fma, redraw, hcp, hcpon, hcpoff, animate, palette,
		   pllist, plus implied screen update
     Multiple:     pldevice, hcpdevice