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Manual Reference Pages  -  XDOT (3)


libxdot - parsing and deparsing of xdot operations




#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 } 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_fill_color, xop_grad_pen_color } 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 */ } u; drawfunc_t drawfunc; };


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

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

xdot_grad_type colorType (char*); xdot_color* parseXDotColor (char*); void freeXDotColor (xdot_color*);


libxdot provides support for parsing and deparsing graphical operations specificed by the xdot language.



This encapsulates a series of cnt xdot operations, stored in the array pointed to by ops. The sz indicates the size of each item stored in ops. If the user sets the freefunc field, this function will be called on each item in ops during freeXDot 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 xdot_op structure.


A value of this type represents one xdot operation. The operation is specified by the kind field. The corresponding data is stored in the union u, with the subfield associated with a given kind indicated by the comments.

The drawfunc 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 parseXDotF.


This type provides an enumeration of the allowed xdot operations. See
for the specific semantics associated with each operation.


This represents a rectangle. For ellipses, the x and x fields represent the center of the rectangle, and w and h give the half-width and half-height, respectively. For images, (x,y) gives the lower left corner of the rectangle, and w and h give the width and height, respectively.


This type encapsulates a series of cnt points.


A value of this type corresponds to printing the string text using the baseline point (x,y). The width field gives an approximation of how wide the printed string will be using the current font and font size. The align field indicates how the text should be horizontally aligned with the point (x,y).


This denotes the insertion of an image. The image source is given by name. The images is to be placed into the rectangle pos.


The fields give the name and size, in points, of a font.


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.


    xdot* parseXDotF (char *str, drawfunc_t* opfns, int sz)

Parses the string str as a sequence of xdot operations and returns a pointer to the resulting xdot structure. The function parses as many xdot operations as it can. If some unknown or incorrect input was encountered in str, the ops and cnt fields will reflect the operations parsed before the error, and the XDOT_PARSE_ERROR bit will be set in the flags field. The function returns NULL if it cannot parse anything.

If sz is non-zero, it is assumed to be the size of some structure type containing xdot_op as a prefix. In this case, the elements in the array pointed to by ops will each have size sz.

If opfns is non-zero, it is taken to be any array of functions indexed by xop_kind. During parsing, the drawfunc member of xop_op will be set to the corresponding function in opfns.

    xdot* parseXDot (char *str)

This is equivalent to parseXDotF(str, 0, 0) .

    void freeXDot (xdot* xp)

This frees the resources associated with the argument. If xp is NULL, nothing happens.

    extern char* sprintXDot (xdot* xp)

    extern void fprintXDot (FILE* fp, xdot* xp)

These two functions deparse the argument xdot structure, producing a string representation. fprintXDot writes the output onto the open stream fp; sprintXDot returns a heap-allocated string.

The color string with fill and draw operations can encode linear and radial gradients. These values are parsed automatically by parseXDotF or parseXDot, with xdot_op having kind xd_grad_pen_color or xd_grad_fill_color and the value is stored in grad_color.

For an application that handles its own parsing of xdot, the library provides three helper functions.

    xdot_grad_type colorTypeXDot (char *str)

returns the color type described by the input string.

    char* parseXDotColor (char *str, xdot_color* clr)

attempts to parse the string str as a color value, storing the result in clr. It returns NULL on failure.

    void freeXDotColor (xdot_color* cp)

This frees the resources associated with a value of type xdot_color.


Although some small checking is done on the sz argument to parseXDotF, it is assumed it is a valid value from sizeof applied to some structure type containing xdot_op as its first field. There can be no validation of the opfns argument.


Emden R. Gansner (
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--> LIBXDOT (3) 31 JULY 2009

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