source/texk/kpathsea/magstep.h

   1 /* magstep.h: declaration for magstep fixing.
   2
   3    Copyright 1994, 2008, 2009 Karl Berry.
   4    Copyright 1999, 2005 Olaf Weber.
   5
   6    This library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    This library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public License
  17    along with this library; if not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef KPATHSEA_MAGSTEP_H
  20 #define KPATHSEA_MAGSTEP_H
  21
  22 #include <kpathsea/c-proto.h>
  23 #include <kpathsea/types.h>
  24
  25 #ifdef __cplusplus
  26 extern "C" {
  27 #endif
  28
  29 /* If DPI is close enough to some magstep of BDPI, return the true dpi
  30    value, and the magstep found (or zero) in M_RET (if
  31    non-null). ``Close enough'' means within one pixel.
  32
  33    M_RET is slightly encoded: the least significant bit is on for a
  34    half-magstep, off otherwise.  Thus, a returned M_RET of 1 means
  35    \magstephalf, i.e., sqrt(1.2), i.e., 1.09544.  Put another way,
  36    return twice the number of magsteps.
  37
  38    In practice, this matters for magstephalf.  Floating-point computation
  39    with the fixed-point DVI representation leads to 328 (for BDPI ==
  40    300); specifying `at 11pt' yields 330; the true \magstephalf is 329
  41    (that's what you get if you run Metafont with mag:=magstep(.5)).
  42
  43    The time to call this is after you read the font spec from the DVI
  44    file, but before you look up any files -- do the usual floating-point
  45    computations, and then fix up the result.  */
  46
  47 extern KPSEDLL unsigned kpathsea_magstep_fix (kpathsea kpse, unsigned dpi,
  48                                               unsigned bdpi, int *m_ret);
  49
  50 #if defined (KPSE_COMPAT_API)
  51 extern KPSEDLL unsigned kpse_magstep_fix (unsigned dpi, unsigned bdpi,
  52                                           int *m_ret);
  53 #endif
  54
  55 #ifdef __cplusplus
  56 }
  57 #endif
  58
  59 #endif /* not KPATHSEA_MAGSTEP_H */