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Annotation of 43BSD/contrib/X/doc/Xlib/ch09a.t, revision 1.1

1.1     ! root        1: .NH
        !             2: Fonts and Information about Fonts
        !             3: .XS
        !             4: Fonts and Information about Fonts
        !             5: .XE
        !             6: .PP
        !             7: .IN "Font Loading"
        !             8: WARNING:  This section WILL change in major ways soon,
        !             9: to provide a more sophisticated view of fonts,
        !            10: and lift limitations in the current font format.
        !            11: Please plan accordingly.
        !            12: .PP
        !            13: The X server loads fonts whenever a program requests a new font.
        !            14: Fonts are unloaded when the last program using the font exits or
        !            15: closes it.
        !            16: There is never more than one copy of a font stored in the server at
        !            17: one time.
        !            18: .PP
        !            19: There are several levels one can deal with fonts.
        !            20: .IN "XOpenFont"
        !            21: .IN "XCloseFont"
        !            22: You can use the general font routines \fIXOpenFont\fP and \fIXCloseFont\fP,
        !            23: or only get the information you want explicitly.
        !            24: .IN "FontInfo"
        !            25: .FD
        !            26: .IN "Definitions" "XOpenFont"
        !            27: .IN "XOpenFont"
        !            28: FontInfo *XOpenFont(name)
        !            29:        char *name;
        !            30: .FN
        !            31: .IN "XGetFont"
        !            32: .IN "XQueryFont"
        !            33: .IN "XFontWidths"
        !            34: This function does a \fIXGetFont\fP, 
        !            35: \fIXQueryFont\fP and \fIXFontWidths\fP in one operation,
        !            36: creating an instance of the font structure.
        !            37: It allocates the memory to store the font information in.
        !            38: It returns NULL if it could not succeed.
        !            39: .FD
        !            40: .IN "Definitions" "XCloseFont"
        !            41: .IN "XCloseFont"
        !            42: XCloseFont(info)
        !            43:        FontInfo *info;
        !            44: .FN
        !            45: This function closes off any use of a font, and deallocates the storage
        !            46: associated with the \fIFontInfo\fP structure.
        !            47: .IN "XOpenFont"
        !            48: WARNING: it is a gross error to close a font not opened with \fIXOpenFont\fP,
        !            49: since you may corrupt the memory pool.
        !            50: .FD
        !            51: .IN "Definitions" "XGetFont"
        !            52: .IN "XGetFont"
        !            53: Font XGetFont (name)
        !            54:        char *name;     /* null-terminated string */
        !            55: .FN
        !            56: \fIXGetFont\fP loads a font of the specified \fIname\fP.
        !            57: A font id is returned, or 0 if it could not succeed.
        !            58: .IN "XFreeFont"
        !            59: The client should call \fIXFreeFont\fP when it is no longer needed.
        !            60: .FD
        !            61: .IN "Definitions" "XQueryFont"
        !            62: .IN "XQueryFont"
        !            63: Status XQueryFont (font, info)
        !            64:        Font font;
        !            65:        FontInfo *info; /* RETURN */
        !            66: .FN
        !            67: \fIXQueryFont\fP gets various facts about a font.  It fills in the
        !            68: client-passed \fIFontInfo\fP, which is defined as follows:
        !            69: .sp
        !            70: .DS
        !            71: .TA .5i 2.5i
        !            72: .ta .5i 2.5i
        !            73: typedef struct _FontInfo {
        !            74:        Font id;        /* font id for this font */
        !            75:        short height;   /* constant for all characters in font */
        !            76:        short width;    /* "average" width of characters in font */
        !            77:        short baseline; /* baseline of characters */
        !            78:        short fixedwidth;       /* 0 or 1 */
        !            79:        unsigned char firstchar, lastchar;      /* first & last characters in font */
        !            80:        short *widths;  /* pointer to font width array */
        !            81: } FontInfo;
        !            82: .DE
        !            83: .IN "Data Structures" "FontInfo"
        !            84: .IN "FontInfo"
        !            85: The \fIbaseline\fP specifies where in pixels from the bottom of the font the
        !            86: characters without descenders begin.
        !            87: .PP
        !            88: A font is fixed width if all characters in the range of legal characters
        !            89: are the same width.
        !            90: .PP
        !            91: It does NOT get the width array, but the space is in the
        !            92: data structure for a pointer to the array.
        !            93: .FD
        !            94: .IN "Definitions" "XFreeFont"
        !            95: .IN "XFreeFont"
        !            96: XFreeFont (font)
        !            97:        Font font;
        !            98: .FN
        !            99: \fIXFreeFont\fP tells the server that this font is no longer needed. 
        !           100: The font may be unloaded on the server if this is the last
        !           101: reference to the font.
        !           102: In any case, the
        !           103: font should never again be referenced.
        !           104: .FD
        !           105: .IN "Definitions" "XCharWidths"
        !           106: .IN "XCharWidths"
        !           107: Status XCharWidths (chars, len, font, widths)
        !           108:        char *chars;    /* NOT necessarily null-terminated */
        !           109:        int len;        /* number of characters */
        !           110:        Font font;
        !           111:        short *widths;  /* RETURN widths [0..len-1] */
        !           112: .FN
        !           113: \fIXCharWidths\fP determines the width, in the specified font, of each
        !           114: character in a string.
        !           115: For each element of the character array, the width of
        !           116: that character is stored in the corresponding element of the \fIwidths\fP
        !           117: array (i.e. widths[i] is set to the width of the character chars[i].)
        !           118: .FD
        !           119: .IN "Definitions" "XFontWidths"
        !           120: .IN "XFontWidths"
        !           121: short *XFontWidths (font)
        !           122:        Font font;
        !           123: .FN
        !           124: \fIXFontWidths\fP allocates and returns a pointer to an array containing the
        !           125: width of every character defined in the font.   
        !           126: It is only possible to get the widths of a variable width font. 
        !           127: If \fIXFontWidths\fP returns NULL, an error has occurred and no
        !           128: array is allocated.
        !           129: The client must free this array when he no longer
        !           130: needs it.
        !           131: .PP
        !           132: .IN "XFontWidths"
        !           133: .IN "XQueryFont"
        !           134: \fIXFontWidths\fP should be used in conjunction with \fIXQueryFont\fP,
        !           135: which returns
        !           136: (among other data) the font's \fIfirstchar\fP and \fIlastchar\fP.
        !           137: The length of the array
        !           138: .IN "XFontWidths"
        !           139: returned by \fIXFontWidths\fP will always be equal to (lastchar-firstchar+1).
        !           140: In the array, widths[i] will be set to the width of character (firstchar+i).
        !           141: .FD
        !           142: .IN "XQueryWidth"
        !           143: .IN "Definitions" "XQueryFont"
        !           144: int XQueryWidth(str, font)
        !           145:        char *str;      /* null-terminated string */
        !           146:        Font font;
        !           147: .FN
        !           148: \fIXQueryWidth\fP returns the width in pixels of a null-terminated string in
        !           149: the specified font.
        !           150: It queries the server for the width computation.
        !           151: .FD
        !           152: .IN "XQueryWidth"
        !           153: .IN "Definitions" "XQueryFont"
        !           154: int XStringWidth(string, info, charpad, spacepad)
        !           155:        char *str;
        !           156:        FontInfo *info;
        !           157:        int charpad, spacepad;
        !           158: .FN
        !           159: This function computes the width of the string given a complete
        !           160: .IN "FontInfo"
        !           161: \fIFontInfo\fP structure.
        !           162: \fICharpad\fP and \fIspacepad\fP are added to the width on each
        !           163: character and space defined in the string.
        !           164: It does not reference the window system server, as the information is
        !           165: all available locally in this case.

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