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XFT - X FreeType interface library


Xft is a simple library designed to interface the FreeType rasterizer with the X Rendering Extension. This manual page barely scratches the surface of this library.


XftPattern holds a set of names with associated value lists; each name refers to a property of a font. XftPatterns are used as inputs to the matching code as well as holding information about specific fonts.

XftFont contains general font metrics and a pointer to either the core XFontStruct data or a structure holding FreeType and X Render Extension data.

XftFontStruct contains information about FreeType fonts used with the X Render Extension.

XftFontSet contains a list of XftPatterns. Internally Xft uses this data structure to hold sets of fonts. Externally, Xft returns the results of listing fonts in this format.

XftObjectSet holds a set of names and is used to specify which fields from fonts are placed in the the list of returned patterns when listing fonts.

XftDraw is an opaque object which holds information used to render to an X drawable using either core protocol or the X Rendering extension.


XftFont *
XftFontOpen (Display *dpy, int screen, ...);
XftFontOpen takes a list of pattern elements of the form (field, type, value) terminated with a 0, matches that pattern against the available fonts and opens the matching font.

   font = XftFontOpen (dpy, scr,
            XFT_FAMILY, XftTypeString, "charter",
            XFT_SIZE, XftTypeDouble, 12.0);

This opens the charter font at 12 points. The point size is automatically converted to the correct pixel size based on the resolution of the monitor.

XftTextExtents8 (Display    *dpy,
         XftFont    *font,
         unsigned char  *string, 
         int        len,
         XGlyphInfo    *extents);
XftTextExtents8 computes the pixel extents of "string" when drawn with "font".

XftDraw *
XftDrawCreate (Display   *dpy,
           Drawable  drawable,
           Visual    *visual,
           Colormap  colormap);
XtDrawCreate creates a structure that can be used to render text and rectangles to the screen.

XftDrawString8 (XftDraw        *d,
        XRenderColor    *color,
        XftFont        *font,
        int        x, 
        int        y,
        unsigned char    *string,
        int        len);
XftDrawString8 draws "string" using "font" in "color" at "x, y".

XftDrawRect (XftDraw        *d,
         XRenderColor   *color,
         int        x, 
         int        y,
         unsigned int   width,
         unsigned int   height);
XftDrawRect fills a solid rectangle in the specified color.


The XftConfig file contains configuration information for the Xft library consisting of directories to look at for font information as well as instructions on editing program specified font patterns before attempting to match the available fonts.

config    :   "dir" STRING
    |   "include" STRING
    |   "includeif" STRING
    |   "match" tests "edit" edits
qual    :   "any"
    |   "all"
edit    :   FIELD-NAME ASSIGN expr SEMI

STRINGs are double-quote delimited. FIELD-NAMEs are identifiers, ASSIGN is one of "=", "+=" or "=+". expr can contain the usual arithmetic operators and can include FIELD-NAMEs.

"dir" adds a directory to the list of places Xft will look for fonts. There is no particular order implied by the list; Xft treats all fonts about the same.

"include" and "includeif" cause Xft to load more configuration parameters from the indicated file. "includeif" doesn't elicit a complaint if the file doesn't exist. If the file name begins with a '~' character, it refers to a path relative to the home directory of the user.

If the tests in a "match" statement all match a user-specified pattern, the pattern will be edited with the specified instructions.

Where ASSIGN is "=", the matching value in the pattern will be replaced by the given expression. "+="/"=+" will prepend/append a new value to the list of values for the indicated field.


As of version 2, Xft has become relatively stable and is expected to retain source and binary compatibility in future releases.


Keith Packard, member of the XFree86 Project, Inc.

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