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.
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(3tk), MeasureChar(3tk)
KEYWORDS¶
font, measurement, Postscript