Tk_FontId(3) Tk Library Procedures Tk_FontId(3)
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NAME
Tk_FontId, Tk_GetFontMetrics, Tk_PostscriptFontName - accessor
functions 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
previous 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
corresponds 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
multiple 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,
Helvetica,
Monaco,
New Century Schoolbook,
New York,
Palatino,
Symbol,
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
return 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
below 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(n),
MeasureChar(3)KEYWORDS
font, measurement, Postscript
Tk 8.0 Tk_FontId(3)
