Ubuntu Manpage: Tk_FontId, Tk_GetFontMetrics, Tk_PostscriptFontName

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.

KEYWORDS