The PLplot Plotting Library: Programmer's Reference Manual
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# Chapter 21. API compatibility definition

This chapter presents the formal definition of what is considered to be in the PLplot library API. It is assumed that major new releases of PLplot will have substantial backwards incompatible changes in the API, but the PLplot developers commit to introducing as few as possible of such incompatibilities between minor releases such that stability across those minor releases is practically guaranteed. In all cases where backwards incompatible changes have been introduced, then the library soname will be changed (for operating systems such as Linux that support versioned shared libraries).

The information in this chapter regards version 5.6.1 of PLplot, released on 2006-05-29.

# What is in the API?

The formal definition of the PLplot C API is everything that is defined in the include file `plplot.h`. This includes all the function prototypes, the defined structures and the semantics of the constants. The list of symbols currently exported by the shared library `libplplot.h` that are declared in `plplot.h` is the following:

    plAlloc2dGrid          plgdidev               plscmap1n
    plClearOpts            plgdiori               plscol0
    plFindCommand          plgdiplt               plscolbg
    plFindName             plgesc                 plscolor
    plFree2dGrid           plgfam                 plscompression
    plGetCursor            plgfci                 plsdev
    plGetFlt               plgfile                plsdidev
    plGetInt               plgfnam                plsdimap
    plGetName              plglevel               plsdiori
    plHLS_RGB              plgpage                plsdiplt
    plMergeOpts            plgra                  plsdiplz
    plMinMax2dGrid         plgriddata             plseopH
    plOptUsage             plgspa                 plsesc
    plParseOpts            plgstrm                plsetopt
    plRGB_HLS              plgver                 plsexit
    plResetOpts            plgvpd                 plsfam
    plSetOpt               plgvpw                 plsfci
    plSetUsage             plgxax                 plsfile
    plTranslateCursor      plgyax                 plsfnam
    pl_cmd                 plgzax                 plshade
    pl_setcontlabelformat  plhist                 plshade1
    pl_setcontlabelparam   plhls                  plshades
    pladv                  plhlsrgb               plsmaj
    plarrows               plimage                plsmem
    plaxes                 plinit                 plsmin
    plbin                  pljoin                 plsori
    plbop                  pllab                  plspage
    plbox                  pllightsource          plspause
    plbox3                 plline                 plsstrm
    plcalc_world           plline3                plssub
    plclear                pllsty                 plssym
    plcol0                 plmap                  plstar
    plcol1                 plmeridians            plstart
    plcont                 plmesh                 plstr
    plcpstrm               plmeshc                plstripa
    pldid2pc               plmkstrm               plstripc
    pldip2dc               plmtex                 plstripd
    plend                  plot3d                 plstyl
    plend1                 plot3dc                plsurf3d
    plenv                  plot3dcl               plsurf3dl
    plenv0                 plparseopts            plsvect
    pleop                  plpat                  plsvpa
    plerrx                 plpoin                 plsxax
    plerry                 plpoin3                plsxwin
    plf2eval               plpoly3                plsyax
    plf2eval2              plprec                 plsym
    plf2evalr              plpsty                 plszax
    plfamadv               plptex                 pltext
    plfcont                plreplot               pltr0
    plfill                 plrgb                  pltr1
    plfill3                plrgb1                 pltr2
    plflush                plrgbhls               pltr2p
    plfont                 plsButtonEH            plvasp
    plfontld               plsError               plvect
    plfshade               plsKeyEH               plvpas
    plgDevs                plsabort               plvpor
    plgFileDevs            plsbopH                plvsta
    plgchr                 plschr                 plw3d
    plgcol0                plscmap0               plwid
    plgcolbg               plscmap0n              plwind
    plgcompression         plscmap1               plxormod
    plgdev                 plscmap1l

Another important aspect of compatibility regard the Application Binary Interface (ABI). Backwards compatibility can be broken by changes in the C structures made public through `plplot.h`. Currently, they are:

    typedef struct {
        char *opt;
        int  (*handler)	(char *, char *, void *);
        void *client_data;
        void *var;
        long mode;
        char *syntax;
        char *desc;
    } PLOptionTable;

    typedef struct {
        int type;			/* of event (CURRENTLY UNUSED) */
        unsigned int state;		/* key or button mask */
        unsigned int keysym;	/* key selected */
        unsigned int button;	/* mouse button selected */
        PLINT subwindow;            /* subwindow (alias subpage, alias subplot) number */
        char string[PL_MAXKEY];	/* translated string */
        int pX, pY;			/* absolute device coordinates of pointer */
        PLFLT dX, dY;		/* relative device coordinates of pointer */
        PLFLT wX, wY;		/* world coordinates of pointer */
    } PLGraphicsIn;

    typedef struct {
        PLFLT dxmi, dxma, dymi, dyma;	/* min, max window rel dev coords */
        PLFLT wxmi, wxma, wymi, wyma;	/* min, max window world coords */
    } PLWindow;

    typedef struct {
        unsigned int x, y;			/* upper left hand corner */
        unsigned int width, height;		/* window dimensions */
    } PLDisplay;

    typedef struct {
        PLFLT *f;
        PLINT nx, ny, nz;
    } PLfGrid;

    typedef struct {
        PLFLT **f;
        PLINT nx, ny;
    } PLfGrid2;

    typedef struct {
        PLFLT *xg, *yg, *zg;
        PLINT nx, ny, nz;
    } PLcGrid;

    typedef struct {
        PLFLT **xg, **yg, **zg;
        PLINT nx, ny;
    } PLcGrid2;

    typedef struct {
        unsigned char r;		/* red */
        unsigned char g;		/* green */
        unsigned char b;		/* blue */
        char *name;
    } PLColor;

    typedef struct {
        PLFLT h;			/* hue */
        PLFLT l;			/* lightness */
        PLFLT s;			/* saturation */
        PLFLT p;			/* position */
        int rev;			/* if set, interpolate through h=0 */
    } PLControlPt;

    typedef struct {
        PLINT cmd;
        PLINT result;
    } PLBufferingCB;

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