NAME¶
Tk_FontId, Tk_GetFontMetrics, Tk_PostscriptFontName - accessor functions for
fonts
SYNOPSIS¶
#include <tk.h>
Font
Tk_FontId(tkfont)
void
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.
- 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 Postcript
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
linespace 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.
KEYWORDS¶
font