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 met
rics for tkfont will
be stored.
Tcl_DString *dsPtr (out) Pointer to an initial
ized 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 lines
pace 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
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 ``reason
able'' Postscript printer, the following screen font fami
lies 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_GetFont |
Metrics 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 let |
ter 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
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