1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 /*
27 *
28 * (C) Copyright IBM Corp. 2003 - All Rights Reserved
29 */
30
31 package sun.font;
32
33 /**
34 * Iterates over runs of fonts in a CompositeFont, optionally taking script runs into account.
35 */
36 public final class FontRunIterator {
37 CompositeFont font;
38 char[] text;
39 int start;
40 int limit;
41
42 CompositeGlyphMapper mapper; // handy cache
43
44 int slot = -1;
45 int pos;
46
47 public void init(CompositeFont font, char[] text, int start, int limit) {
48 if (font == null || text == null || start < 0 || limit < start || limit > text.length) {
49 throw new IllegalArgumentException();
50 }
51
52 this.font = font;
53 this.text = text;
54 this.start = start;
55 this.limit = limit;
56
57 this.mapper = (CompositeGlyphMapper)font.getMapper();
58 this.slot = -1;
59 this.pos = start;
60 }
61
62 public PhysicalFont getFont() {
63 return slot == -1 ? null : font.getSlotFont(slot);
64 }
65
66 public int getGlyphMask() {
67 return slot << 24;
68 }
69
70 public int getPos() {
71 return pos;
72 }
73
74 /*
75 * characters that are in the 'common' script become part of the
76 * surrounding script run. we want to fetch these from the same font
77 * used to get surrounding characters, where possible. but we don't
78 * want to force non-common characters to come from other than their
79 * standard font.
80 *
81 * what we really want to do is this:
82 * 1) fetch a code point from the text.
83 * 2) get its 'native' script code
84 * 3) determine its 'resolved' script code
85 * 4) if its native script is COMMON, and its resolved script is the same as the previous
86 * code point's, then see if the previous font supports this code point. if so, use it.
87 * 5) otherwise resolve the font as usual
88 * 6) break the run when either the physical font or the resolved script changes.
89 *
90 * problems: we optimize latin-1 and cjk text assuming a fixed
91 * width for each character. since latin-1 digits and punctuation
92 * are common, following this algorithm they will change to match
93 * the fonts used for the preceding text, and potentially change metrics.
94 *
95 * this also seems to have the potential for changing arbitrary runs of text, e.g.
96 * any number of digits and spaces can change depending on the preceding (or following!)
97 * non-COMMON character's font assignment. this is not good.
98 *
99 * since the goal is to enable layout to be performed using as few physical fonts as
100 * possible, and the primary cause of switching fonts is to handle spaces, perhaps
101 * we should just special-case spaces and assign them from the current font, whatever
102 * it may be.
103 *
104 * One could also argue that the job of the composite font is to assign physical fonts
105 * to text runs, however it wishes. we don't necessarily have to provide script info
106 * to let it do this. it can determine based on whatever. so having a special 'next'
107 * function that takes script (and limit) is redundant. It can fetch the script again
108 * if need be.
109 *
110 * both this and the script iterator are turning char sequences into code point
111 * sequences. maybe it would be better to feed a single code point into each iterator-- push
112 * the data instead of pull it?
113 */
114
115 public boolean next(int script, int lim) {
116 if (pos == lim) {
117 return false;
118 }
119
120 int ch = nextCodePoint(lim);
121 int sl = mapper.charToGlyph(ch) & CompositeGlyphMapper.SLOTMASK;
122 int secondPosition = pos;
123 int preChar = ch;
124 boolean consumed = false;
125 slot = sl >>> 24;
126 while ((ch = nextCodePoint(lim)) != DONE ) {
127 if (CharToGlyphMapper.isVariationSelector(ch)
128 && CharToGlyphMapper.isBaseChar(preChar)
129 && consumed == false) {
130 consumed = true;
131 int[] chars = {preChar, ch};
132 int[] glyphs = {0, 0};
133 mapper.charsToGlyphs(2, chars, glyphs);
134 int vsSize = 1;
135 if (ch >= 0x10000) vsSize = 2;
136 if (secondPosition + vsSize == pos){ // Real slot
137 sl = glyphs[0] & CompositeGlyphMapper.SLOTMASK;
138 slot = sl >>> 24;
139 }
140 if ((glyphs[0] & CompositeGlyphMapper.SLOTMASK) != sl) {
141 pushback(ch);
142 pushback(preChar);
143 return true;
144 }
145 }else{
146 consumed = false;
147 if ((mapper.charToGlyph(ch) & CompositeGlyphMapper.SLOTMASK) != sl) {
148 break;
149 }
150 }
151 preChar = ch;
152 }
153 pushback(ch);
154
155 return true;
156 }
157
158 public boolean next() {
159 return next(Script.COMMON, limit);
160 }
161
162 static final int SURROGATE_START = 0x10000;
163 static final int LEAD_START = 0xd800;
164 static final int LEAD_LIMIT = 0xdc00;
165 static final int TAIL_START = 0xdc00;
166 static final int TAIL_LIMIT = 0xe000;
167 static final int LEAD_SURROGATE_SHIFT = 10;
168 static final int SURROGATE_OFFSET = SURROGATE_START - (LEAD_START << LEAD_SURROGATE_SHIFT) - TAIL_START;
169
170 static final int DONE = -1;
171
172 int nextCodePoint() {
173 return nextCodePoint(limit);
174 }
175
176 int nextCodePoint(int lim) {
177 if (pos >= lim) {
178 return DONE;
179 }
180 int ch = text[pos++];
181 if (ch >= LEAD_START && ch < LEAD_LIMIT && pos < lim) {
182 int nch = text[pos];
183 if (nch >= TAIL_START && nch < TAIL_LIMIT) {
184 ++pos;
185 ch = (ch << LEAD_SURROGATE_SHIFT) + nch + SURROGATE_OFFSET;
186 }
187 }
188 return ch;
189 }
190
191 void pushback(int ch) {
192 if (ch >= 0) {
193 if (ch >= 0x10000) {
194 pos -= 2;
195 } else {
196 pos -= 1;
197 }
198 }
199 }
200 }