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/*
 *
 * (C) Copyright IBM Corp. 2003 - All Rights Reserved
 */

package sun.font;

Iterates over runs of fonts in a CompositeFont, optionally taking script runs into account.
/** * Iterates over runs of fonts in a CompositeFont, optionally taking script runs into account. */
public final class FontRunIterator { CompositeFont font; char[] text; int start; int limit; CompositeGlyphMapper mapper; // handy cache int slot = -1; int pos; public void init(CompositeFont font, char[] text, int start, int limit) { if (font == null || text == null || start < 0 || limit < start || limit > text.length) { throw new IllegalArgumentException(); } this.font = font; this.text = text; this.start = start; this.limit = limit; this.mapper = (CompositeGlyphMapper)font.getMapper(); this.slot = -1; this.pos = start; } public PhysicalFont getFont() { return slot == -1 ? null : font.getSlotFont(slot); } public int getGlyphMask() { return slot << 24; } public int getPos() { return pos; } /* * characters that are in the 'common' script become part of the * surrounding script run. we want to fetch these from the same font * used to get surrounding characters, where possible. but we don't * want to force non-common characters to come from other than their * standard font. * * what we really want to do is this: * 1) fetch a code point from the text. * 2) get its 'native' script code * 3) determine its 'resolved' script code * 4) if its native script is COMMON, and its resolved script is the same as the previous * code point's, then see if the previous font supports this code point. if so, use it. * 5) otherwise resolve the font as usual * 6) break the run when either the physical font or the resolved script changes. * * problems: we optimize latin-1 and cjk text assuming a fixed * width for each character. since latin-1 digits and punctuation * are common, following this algorithm they will change to match * the fonts used for the preceding text, and potentially change metrics. * * this also seems to have the potential for changing arbitrary runs of text, e.g. * any number of digits and spaces can change depending on the preceding (or following!) * non-COMMON character's font assignment. this is not good. * * since the goal is to enable layout to be performed using as few physical fonts as * possible, and the primary cause of switching fonts is to handle spaces, perhaps * we should just special-case spaces and assign them from the current font, whatever * it may be. * * One could also argue that the job of the composite font is to assign physical fonts * to text runs, however it wishes. we don't necessarily have to provide script info * to let it do this. it can determine based on whatever. so having a special 'next' * function that takes script (and limit) is redundant. It can fetch the script again * if need be. * * both this and the script iterator are turning char sequences into code point * sequences. maybe it would be better to feed a single code point into each iterator-- push * the data instead of pull it? */ public boolean next(int script, int lim) { if (pos == lim) { return false; } int ch = nextCodePoint(lim); int sl = mapper.charToGlyph(ch) & CompositeGlyphMapper.SLOTMASK; slot = sl >>> 24; while ((ch = nextCodePoint(lim)) != DONE && (mapper.charToGlyph(ch) & CompositeGlyphMapper.SLOTMASK) == sl); pushback(ch); return true; } public boolean next() { return next(Script.COMMON, limit); } static final int SURROGATE_START = 0x10000; static final int LEAD_START = 0xd800; static final int LEAD_LIMIT = 0xdc00; static final int TAIL_START = 0xdc00; static final int TAIL_LIMIT = 0xe000; static final int LEAD_SURROGATE_SHIFT = 10; static final int SURROGATE_OFFSET = SURROGATE_START - (LEAD_START << LEAD_SURROGATE_SHIFT) - TAIL_START; static final int DONE = -1; final int nextCodePoint() { return nextCodePoint(limit); } final int nextCodePoint(int lim) { if (pos >= lim) { return DONE; } int ch = text[pos++]; if (ch >= LEAD_START && ch < LEAD_LIMIT && pos < lim) { int nch = text[pos]; if (nch >= TAIL_START && nch < TAIL_LIMIT) { ++pos; ch = (ch << LEAD_SURROGATE_SHIFT) + nch + SURROGATE_OFFSET; } } return ch; } final void pushback(int ch) { if (ch >= 0) { if (ch >= 0x10000) { pos -= 2; } else { pos -= 1; } } } }