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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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