font-loader.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 ;;; The font-loader object, which is the primary interface for
  28 ;;; getting glyph and metrics info.
  29 ;;;
  30 ;;; $Id: font-loader.lisp,v 1.26 2006/03/23 22:21:40 xach Exp $
  31
  32 (in-package #:zpb-ttf)
  33
  34 (defclass font-loader ()
  35   ((tables :initform (make-hash-table) :reader tables)
  36    (input-stream :initarg :input-stream :accessor input-stream
  37           :documentation "The stream from which things are loaded.")
  38    (table-count :initarg :table-count :reader table-count)
  39    ;; from the 'head' table
  40    (units/em :accessor units/em)
  41    (bounding-box :accessor bounding-box)
  42    (loca-offset-format :accessor loca-offset-format)
  43    ;; from the 'loca' table
  44    (glyph-locations :accessor glyph-locations)
  45    ;; from the 'cmap' table
  46    (character-map :accessor character-map)
  47    (inverse-character-map :accessor inverse-character-map)
  48    ;; from the 'maxp' table
  49    (glyph-count :accessor glyph-count)
  50    ;; from the 'hhea' table
  51    (ascender :accessor ascender)
  52    (descender :accessor descender)
  53    (line-gap :accessor line-gap)
  54    ;; from the 'hmtx' table
  55    (advance-widths :accessor advance-widths)
  56    (left-side-bearings :accessor left-side-bearings)
  57    ;; from the 'kern' table
  58    (kerning-table :initform (make-hash-table) :accessor kerning-table)
  59    ;; from the 'name' table
  60    (name-entries :initform nil :accessor name-entries)
  61    ;; from the 'post' table
  62    (italic-angle :accessor italic-angle :initform 0)
  63    (fixed-pitch-p :accessor fixed-pitch-p :initform nil)
  64    (underline-position :accessor underline-position :initform 0)
  65    (underline-thickness :accessor underline-thickness :initform 0)
  66    (postscript-glyph-names :accessor postscript-glyph-names)
  67    ;; misc
  68    (glyph-cache :accessor glyph-cache)))
  69
  70 (defclass table-info ()
  71   ((name :initarg :name :reader name)
  72    (offset :initarg :offset :reader offset)
  73    (size :initarg :size :reader size)))
  74
  75 (defmethod print-object ((object table-info) stream)
  76   (print-unreadable-object (object stream :type t)
  77     (format stream "\"~A\"" (name object))))
  78
  79 \f
  80 ;;; tag integers to strings and back
  81
  82 (defun number->tag (number)
  83   "Convert the 32-bit NUMBER to a string of four characters based on
  84 the CODE-CHAR of each octet in the number."
  85   (let ((tag (make-string 4)))
  86     (loop for i below 4
  87           for offset from 24 downto 0 by 8
  88           do (setf (schar tag i)
  89                    (code-char (ldb (byte 8 offset) number))))
  90     tag))
  91
  92 (defun tag->number (tag)
  93   "Convert the four-character string TAG to a 32-bit number based on
  94 the CHAR-CODE of each character."
  95   (declare (simple-string tag))
  96   (loop for char across tag
  97         for offset from 24 downto 0 by 8
  98         summing (ash (char-code char) offset)))
  99
 100 \f
 101 ;;; Getting table info out of the loader
 102
 103 (defmethod table-info ((tag string) (font-loader font-loader))
 104   (gethash (tag->number tag) (tables font-loader)))
 105
 106 (defmethod table-exists-p (tag font-loader)
 107   (nth-value 1 (table-info tag font-loader)))
 108
 109 (defmethod table-position ((tag string) (font-loader font-loader))
 110   "Return the byte position in the font-loader's stream for the table
 111 named by TAG."
 112   (let ((table-info (table-info tag font-loader)))
 113     (if table-info
 114         (offset table-info)
 115         (error "No such table -- ~A" tag))))
 116
 117 (defmethod table-size ((tag string) (font-loader font-loader))
 118   (let ((table-info (table-info tag font-loader)))
 119     (if table-info
 120         (size table-info)
 121         (error "No such table -- ~A" tag))))
 122
 123 (defmethod seek-to-table ((tag string) (font-loader font-loader))
 124   "Move FONT-LOADER's input stream to the start of the table named by TAG."
 125   (file-position (input-stream font-loader) (table-position tag font-loader)))