Tk_FontId(3tk) Tk Library Procedures Tk_FontId(3tk)
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NAME
Tk_FontId, Tk_GetFontMetrics, Tk_PostscriptFontName - accessor func-
tions for fonts
SYNOPSIS
#include <tk.h>
Font
Tk_FontId(tkfont)
Tk_GetFontMetrics(tkfont, fmPtr)
int
Tk_PostscriptFontName(tkfont, dsPtr)
ARGUMENTS
Tk_Font tkfont (in) Opaque font token being queried.
Must have been returned by a previ-
ous call to Tk_GetFont.
Tk_FontMetrics *fmPtr (out) Pointer to structure in which the
font metrics for tkfont will be
stored. See DATA STRUCTURES below
for details.
Tcl_DString *dsPtr (out) Pointer to an initialized
Tcl_DString to which the name of
the Postscript font that corre-
sponds to tkfont will be appended.
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DESCRIPTION
Given a tkfont, Tk_FontId returns the token that should be selected
into an XGCValues structure in order to construct a graphics context
that can be used to draw text in the specified font.
Tk_GetFontMetrics computes the ascent, descent, and linespace of the
tkfont in pixels and stores those values in the structure pointer to by
fmPtr. These values can be used in computations such as to space mul-
tiple lines of text, to align the baselines of text in different fonts,
and to vertically align text in a given region. See the documentation
for the font command for definitions of the terms ascent, descent, and
linespace, used in font metrics.
Tk_PostscriptFontName maps a tkfont to the corresponding Postscript
font name that should be used when printing. The return value is the
size in points of the tkfont and the Postscript font name is appended
to dsPtr. DsPtr must refer to an initialized Tcl_DString. Given a
“reasonable” Postscript printer, the following screen font families
should print correctly:
Avant Garde, Arial, Bookman, Courier, Courier New, Geneva, Hel-
vetica, Monaco, New Century Schoolbook, New York, Palatino, Sym-
bol, Times, Times New Roman, Zapf Chancery, and Zapf Dingbats.
Any other font families may not print correctly because the computed
Postscript font name may be incorrect or not exist on the printer.
DATA STRUCTURES
The Tk_FontMetrics data structure is used by Tk_GetFontMetrics to re-
turn information about a font and is defined as follows:
typedef struct Tk_FontMetrics {
int ascent;
int descent;
int linespace;
} Tk_FontMetrics;
The ascent field is the amount in pixels that the tallest letter sticks
up above the baseline, plus any extra blank space added by the designer
of the font.
The descent is the largest amount in pixels that any letter sticks be-
low the baseline, plus any extra blank space added by the designer of
the font.
The linespace is the sum of the ascent and descent. How far apart two
lines of text in the same font should be placed so that none of the
characters in one line overlap any of the characters in the other line.
SEE ALSO
font(3tk), MeasureChar(3tk)
KEYWORDS
font, measurement, Postscript
Tk 8.0 Tk_FontId(3tk)
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