Provided by: tk8.4-doc_8.4.19-4_all bug


       Tk_FontId, Tk_GetFontMetrics, Tk_PostscriptFontName - accessor functions for fonts


       #include <tk.h>


       Tk_GetFontMetrics(tkfont, fmPtr)

       Tk_PostscriptFontName(tkfont, dsPtr)


       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.


       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.