.TH LIBXDOT 3 "31 JULY 2009"
.SH NAME
\fBlibxdot\fR \- parsing and deparsing of xdot operations
.SH SYNOPSIS
.ta .75i 1.5i 2.25i 3i 3.75i 4.5i 5.25i 6i
.PP
.nf
\f5
#include <graphviz/xdot.h>

typedef enum {
    xd_none,
    xd_linear,
    xd_radial
} xdot_grad_type;

typedef struct {
    float frac;
    char* color;
} xdot_color_stop;

typedef struct {
    double x0, y0;
    double x1, y1;
    int n_stops;
    xdot_color_stop* stops;
} xdot_linear_grad;

typedef struct {
    double x0, y0, r0;
    double x1, y1, r1;
    int n_stops;
    xdot_color_stop* stops;
} xdot_radial_grad;

typedef struct {
    xdot_grad_type type;
    union {
	char* clr;
	xdot_linear_grad ling;
	xdot_radial_grad ring;
    } u;
} xdot_color;

typedef enum {
    xd_left, xd_center, xd_right
} xdot_align;

typedef struct {
    double x, y, z;
} xdot_point;

typedef struct {
    double x, y, w, h;
} xdot_rect;

typedef struct {
    int cnt;
    xdot_point* pts;
} xdot_polyline;

typedef struct {
  double x, y;
  xdot_align align;
  double width;
  char* text;
} xdot_text;

typedef struct {
    xdot_rect pos;
    char* name;
} xdot_image;

typedef struct {
    double size;
    char* name;
} xdot_font;

typedef enum {
    xd_filled_ellipse, xd_unfilled_ellipse,
    xd_filled_polygon, xd_unfilled_polygon,
    xd_filled_bezier,  xd_unfilled_bezier,
    xd_polyline,       xd_text,
    xd_fill_color,     xd_pen_color, xd_font, xd_style, xd_image,
    xd_grad_fill_color,     xd_grad_pen_color,
    xd_fontchar
} xdot_kind; 
    
typedef enum {
    xop_ellipse,
    xop_polygon,
    xop_bezier,
    xop_polyline,       xop_text,
    xop_fill_color,     xop_pen_color, xop_font, xop_style, xop_image,
    xop_grad_color,
    xop_fontchar
} xop_kind; 
    
typedef struct _xdot_op xdot_op;
typedef void (*drawfunc_t)(xdot_op*, int);
typedef void (*freefunc_t)(xdot_op*);

struct _xdot_op {
    xdot_kind kind;
    union {
      xdot_rect ellipse;       /* xd_filled_ellipse, xd_unfilled_ellipse */
      xdot_polyline polygon;   /* xd_filled_polygon, xd_unfilled_polygon */
      xdot_polyline polyline;  /* xd_polyline */
      xdot_polyline bezier;    /* xd_filled_bezier,  xd_unfilled_bezier */
      xdot_text text;          /* xd_text */
      xdot_image image;        /* xd_image */
      char* color;             /* xd_fill_color, xd_pen_color */
      xdot_color grad_color;   /* xd_grad_fill_color, xd_grad_pen_color */
      xdot_font font;          /* xd_font */
      char* style;             /* xd_style */
      unsigned int fontchar;   /* xd_fontchar */
    } u;
    drawfunc_t drawfunc;
};

#define XDOT_PARSE_ERROR 1

typedef struct {
    int cnt;
    int sz;
    xdot_op* ops;
    freefunc_t freefunc;
    int flags;
} xdot;

typedef struct {
    int cnt;  /* no. of xdot ops */
    int n_ellipse;
    int n_polygon;
    int n_polygon_pts;
    int n_polyline;
    int n_polyline_pts;
    int n_bezier;
    int n_bezier_pts;
    int n_text;
    int n_font;
    int n_style;
    int n_color;
    int n_image;
    int n_gradcolor;
    int n_fontchar;
} xdot_stats;

xdot* parseXDotF (char*, drawfunc_t opfns[], int sz);
xdot* parseXDotFOn (char*, drawfunc_t opfns[], int sz, xdot*);
xdot* parseXDot (char*);
char* sprintXDot (xdot*);
void fprintXDot (FILE*, xdot*);
void jsonXDot (FILE*, xdot*);
void freeXDot (xdot*);
int statXDot (xdot*, xdot_stats*);

xdot_grad_type colorType (char*);
xdot_color* parseXDotColor (char*);
void freeXDotColor (xdot_color*);
\fP
.fi
.SH DESCRIPTION
\fIlibxdot\fP provides support for parsing and deparsing
graphical operations specified by the \fIxdot\fP language.
.SS "Types"
.PP
.SS "  xdot"
This encapsulates a series of \fIcnt\fP xdot operations, stored
in the array pointed to by \fIops\fP. The \fIsz\fP indicates
the size of each item stored in \fIops\fP. If the user sets
the \fIfreefunc\fP field, this function will be called on each
item in \fIops\fP during \fIfreeXDot\fP before the library does
its own clean up of the item. This allows the user to free any
resources stored in the item by using an expansion of the \fIxdot_op\fP
structure. 
.PP
.SS "  xdot_op"
A value of this type represents one xdot operation. The operation
is specified by the \fIkind\fP field. The corresponding data is
stored in the union \fIu\fP, with the subfield associated with
a given \fIkind\fP indicated by the comments. 
.PP
The \fIdrawfunc\fP field allows the user to attach a drawing-specific
function to the operation, providing an object-based interface. These
functions can be automatically attached during parsing by providing a
non-NULL second argument to \fBparseXDotF\fP.
.PP
.SS "  xop_kind"
This type provides an enumeration of the allowed xdot operations.
See 
.br
    https://graphviz.org/docs/outputs/canon/#xdot
.br
for the specific semantics associated with each operation.
.PP
.SS "  xdot_rect"
This represents a rectangle. For ellipses,
the \fIx\fP and \fIx\fP fields represent the center of the rectangle,
and \fIw\fP and \fIh\fP give the half-width and half-height, respectively.
For images, (\fIx\fP,\fIy\fP) gives the lower left corner of the
rectangle, and \fIw\fP and \fIh\fP give the width and height, respectively.
.PP
.SS "  xdot_polyline"
This type encapsulates a series of \fIcnt\fP points.
.PP
.SS "  xdot_text"
A value of this type corresponds to printing the string \fItext\fP
using the baseline point (\fIx\fP,\fIy\fP).
The \fIwidth\fP field gives an approximation of how wide the printed
string will be using the current font and font size.
The \fIalign\fP field indicates how the text should be horizontally 
aligned with the point (\fIx\fP,\fIy\fP).
.PP
.SS "  xdot_image"
This denotes the insertion of an image. The image source is
given by \fIname\fP. The images is to be placed into the rectangle
\fIpos\fP.
.PP
.SS "  xdot_font"
The fields give the name and size, in points, of a font.
.PP
.SS "  xdot_align"
This enumeration type corresponds to the xdot alignment values
-1, 0 and 1 used with the text operator, or '\\l', '\\n' and '\\r'
used in dot text.
.SS "Functions"
.PP
.SS "  xdot* parseXDotF (char *str, drawfunc_t* opfns, int sz)"
Parses the string \fIstr\fP as a sequence of xdot operations
and returns a pointer to the resulting \fIxdot\fP structure.
The function parses as many xdot operations as it can. If some
unknown or incorrect input was encountered in \fIstr\fP,  
the \fIops\fP and \fIcnt\fP fields will reflect the operations
parsed before the error, and
the \fIXDOT_PARSE_ERROR\fP bit will be set in the \fIflags\fP field.
The function returns NULL if it cannot parse anything.
.PP
If \fIsz\fP is non-zero, it is assumed to be the size of some
structure type containing \fIxdot_op\fP as a prefix. In this case,
the elements in the array pointed to by \fIops\fP will each have
size \fIsz\fP.
.PP
If \fIopfns\fP is non-zero, it is taken to be any array of functions
indexed by \fIxop_kind\fP. During parsing, the \fIdrawfunc\fP member
of \fIxop_op\fP will be set to the corresponding function in \fIopfns\fP.
.PP
.SS "  xdot* parseXDotFOn (char *str, drawfunc_t* opfns, int sz, xdot* x)"
The same as \fIparseXDotF\fP, but append to the given \fIxdot\fP object \fIx\fP.
.PP
.SS "  xdot* parseXDot (char *str)"
This is equivalent to \fIparseXDotF(str, 0, 0)\fP .
.PP
.SS "  void freeXDot (xdot* xp)"
This frees the resources associated with the argument.
If \fIxp\fP is NULL, nothing happens.
.PP
.SS "  extern char* sprintXDot (xdot* xp)"
.SS "  extern void fprintXDot (FILE* fp, xdot* xp)"
These two functions deparse the argument xdot structure, producing
a string representation. \fIfprintXDot\fP writes the output onto
the open stream \fIfp\fP; \fIsprintXDot\fP returns a heap-allocated
string.
.PP
The color string with fill and draw operations can encode linear
and radial gradients. These values are parsed automatically by
\fBparseXDotF\fP or \fBparseXDot\fP, 
with \fIxdot_op\fP having kind \fIxd_grad_pen_color\fP or
\fIxd_grad_fill_color\fP and the value is stored in \fIgrad_color\fP.
.PP
For an application that handles its own parsing of xdot, the library
provides three helper functions.
.PP
.SS "  void jsonXDot(FILE * fp, xdot * x)"
Translate a given \fIxdot\fP object to a JSON representation. This functionality
is currently considered experimental and the format of the JSON output may not
be stable across Graphviz releases.
.PP
.SS "  xdot_grad_type colorTypeXDot (char *str)"
returns the color type described by the input string.
.PP
.SS "  char* parseXDotColor (char *str, xdot_color* clr)"
attempts to parse the string \fIstr\fP as a color value, storing
the result in \fIclr\fP. It returns NULL on failure.
.PP
.SS "  void freeXDotColor (xdot_color* cp)"
This frees the resources associated with a value of type \fIxdot_color\fP.
.PP
.SS "  int statXDot (xdot *x, xdot_stats *sp)"
This function is provided for retrieving various statistics about an \fIxdot\fP
object. Returns 0 on success and populates the output parameter \fIsp\fP with
counts of various entities in the \fIxdot\fP object.

.SH BUGS
Although some small checking is done on the \fIsz\fP argument to
\fIparseXDotF\fP, it is assumed it is a valid value from \fIsizeof\fP
applied to some structure type containing \fIxdot_op\fP as its first
field. There can be no validation of the \fIopfns\fP argument.
.SH AUTHORS
Emden R. Gansner (erg@research.att.com).