head.lisp

   1 ;;; Copyright (c) 2006 Zachary Beane, All Rights Reserved
   2 ;;;
   3 ;;; Redistribution and use in source and binary forms, with or without
   4 ;;; modification, are permitted provided that the following conditions
   5 ;;; are met:
   6 ;;;
   7 ;;;   * Redistributions of source code must retain the above copyright
   8 ;;;     notice, this list of conditions and the following disclaimer.
   9 ;;;
  10 ;;;   * Redistributions in binary form must reproduce the above
  11 ;;;     copyright notice, this list of conditions and the following
  12 ;;;     disclaimer in the documentation and/or other materials
  13 ;;;     provided with the distribution.
  14 ;;;
  15 ;;; THIS SOFTWARE IS PROVIDED BY THE AUTHOR 'AS IS' AND ANY EXPRESSED
  16 ;;; OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  17 ;;; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  18 ;;; ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
  19 ;;; DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  20 ;;; DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  21 ;;; GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  22 ;;; INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  23 ;;; WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  24 ;;; NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  25 ;;; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26 ;;;
  27 ;;; Loading data from the "head" table.
  28 ;;;
  29 ;;;  http://www.microsoft.com/OpenType/OTSpec/head.htm
  30 ;;;  http://developer.apple.com/fonts/TTRefMan/RM06/Chap6head.html
  31 ;;;
  32 ;;; $Id: head.lisp,v 1.5 2006/02/18 23:13:43 xach Exp $
  33
  34 (in-package #:zpb-ttf)
  35
  36 (defmethod load-head-info ((font-loader font-loader))
  37   (seek-to-table "head" font-loader)
  38   (with-slots (input-stream units/em bounding-box loca-offset-format)
  39       font-loader
  40     (flet ((skip-bytes (count)
  41              (file-position input-stream (+ count
  42                                             (file-position input-stream)))))
  43       (let ((version (read-uint32 input-stream)))
  44         (check-version "\"head\" table" version #x00010000))
  45       ;; skip fontRevsion and checkSumAdjustment (both uint32)
  46       (skip-bytes 8)
  47       ;; check the magicNumber
  48       (let ((magic-number (read-uint32 input-stream)))
  49         (when (/= magic-number #x5F0F3CF5)
  50           (error 'bad-magic
  51                  :location "\"head\" table"
  52                  :expected-values (list #x5F0F3CF5)
  53                  :actual-value magic-number)))
  54       ;; skip flags
  55       (skip-bytes 2)
  56       (setf units/em (read-uint16 input-stream))
  57       ;; skip created and modified dates
  58       (skip-bytes 16)
  59       (setf bounding-box (vector (read-int16 input-stream)
  60                                  (read-int16 input-stream)
  61                                  (read-int16 input-stream)
  62                                  (read-int16 input-stream)))
  63       ;; skip macStyle, lowestRecPPEM, fontDirectionHint
  64       (skip-bytes 6)
  65       ;; set the loca-offset-format
  66       (if (zerop (read-int16 input-stream))
  67           (setf loca-offset-format :short)
  68           (setf loca-offset-format :long)))))