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335 lines
13 KiB
335 lines
13 KiB
/*
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* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*
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*/
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/*
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* (C) Copyright IBM Corp. 1999-2003 - All Rights Reserved
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*
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* The original version of this source code and documentation is
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* copyrighted and owned by IBM. These materials are provided
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* under terms of a License Agreement between IBM and Sun.
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* This technology is protected by multiple US and International
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* patents. This notice and attribution to IBM may not be removed.
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*/
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package java.text;
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import sun.text.bidi.BidiBase;
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/**
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* This class implements the Unicode Bidirectional Algorithm.
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* <p>
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* A Bidi object provides information on the bidirectional reordering of the text
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* used to create it. This is required, for example, to properly display Arabic
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* or Hebrew text. These languages are inherently mixed directional, as they order
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* numbers from left-to-right while ordering most other text from right-to-left.
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* <p>
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* Once created, a Bidi object can be queried to see if the text it represents is
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* all left-to-right or all right-to-left. Such objects are very lightweight and
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* this text is relatively easy to process.
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* <p>
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* If there are multiple runs of text, information about the runs can be accessed
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* by indexing to get the start, limit, and level of a run. The level represents
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* both the direction and the 'nesting level' of a directional run. Odd levels
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* are right-to-left, while even levels are left-to-right. So for example level
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* 0 represents left-to-right text, while level 1 represents right-to-left text, and
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* level 2 represents left-to-right text embedded in a right-to-left run.
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*
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* @since 1.4
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*/
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public final class Bidi {
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/** Constant indicating base direction is left-to-right. */
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public static final int DIRECTION_LEFT_TO_RIGHT = 0;
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/** Constant indicating base direction is right-to-left. */
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public static final int DIRECTION_RIGHT_TO_LEFT = 1;
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/**
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* Constant indicating that the base direction depends on the first strong
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* directional character in the text according to the Unicode
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* Bidirectional Algorithm. If no strong directional character is present,
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* the base direction is left-to-right.
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*/
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public static final int DIRECTION_DEFAULT_LEFT_TO_RIGHT = -2;
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/**
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* Constant indicating that the base direction depends on the first strong
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* directional character in the text according to the Unicode
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* Bidirectional Algorithm. If no strong directional character is present,
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* the base direction is right-to-left.
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*/
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public static final int DIRECTION_DEFAULT_RIGHT_TO_LEFT = -1;
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private BidiBase bidiBase;
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/**
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* Create Bidi from the given paragraph of text and base direction.
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* @param paragraph a paragraph of text
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* @param flags a collection of flags that control the algorithm. The
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* algorithm understands the flags DIRECTION_LEFT_TO_RIGHT, DIRECTION_RIGHT_TO_LEFT,
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* DIRECTION_DEFAULT_LEFT_TO_RIGHT, and DIRECTION_DEFAULT_RIGHT_TO_LEFT.
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* Other values are reserved.
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*/
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public Bidi(String paragraph, int flags) {
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if (paragraph == null) {
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throw new IllegalArgumentException("paragraph is null");
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}
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bidiBase = new BidiBase(paragraph.toCharArray(), 0, null, 0, paragraph.length(), flags);
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}
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/**
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* Create Bidi from the given paragraph of text.
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* <p>
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* The RUN_DIRECTION attribute in the text, if present, determines the base
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* direction (left-to-right or right-to-left). If not present, the base
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* direction is computes using the Unicode Bidirectional Algorithm, defaulting to left-to-right
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* if there are no strong directional characters in the text. This attribute, if
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* present, must be applied to all the text in the paragraph.
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* <p>
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* The BIDI_EMBEDDING attribute in the text, if present, represents embedding level
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* information. Negative values from -1 to -62 indicate overrides at the absolute value
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* of the level. Positive values from 1 to 62 indicate embeddings. Where values are
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* zero or not defined, the base embedding level as determined by the base direction
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* is assumed.
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* <p>
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* The NUMERIC_SHAPING attribute in the text, if present, converts European digits to
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* other decimal digits before running the bidi algorithm. This attribute, if present,
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* must be applied to all the text in the paragraph.
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*
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* @param paragraph a paragraph of text with optional character and paragraph attribute information
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*
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* @see java.awt.font.TextAttribute#BIDI_EMBEDDING
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* @see java.awt.font.TextAttribute#NUMERIC_SHAPING
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* @see java.awt.font.TextAttribute#RUN_DIRECTION
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*/
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public Bidi(AttributedCharacterIterator paragraph) {
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if (paragraph == null) {
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throw new IllegalArgumentException("paragraph is null");
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}
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bidiBase = new BidiBase(0, 0);
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bidiBase.setPara(paragraph);
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}
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/**
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* Create Bidi from the given text, embedding, and direction information.
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* The embeddings array may be null. If present, the values represent embedding level
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* information. Negative values from -1 to -61 indicate overrides at the absolute value
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* of the level. Positive values from 1 to 61 indicate embeddings. Where values are
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* zero, the base embedding level as determined by the base direction is assumed.
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* @param text an array containing the paragraph of text to process.
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* @param textStart the index into the text array of the start of the paragraph.
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* @param embeddings an array containing embedding values for each character in the paragraph.
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* This can be null, in which case it is assumed that there is no external embedding information.
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* @param embStart the index into the embedding array of the start of the paragraph.
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* @param paragraphLength the length of the paragraph in the text and embeddings arrays.
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* @param flags a collection of flags that control the algorithm. The
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* algorithm understands the flags DIRECTION_LEFT_TO_RIGHT, DIRECTION_RIGHT_TO_LEFT,
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* DIRECTION_DEFAULT_LEFT_TO_RIGHT, and DIRECTION_DEFAULT_RIGHT_TO_LEFT.
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* Other values are reserved.
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*/
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public Bidi(char[] text, int textStart, byte[] embeddings, int embStart, int paragraphLength, int flags) {
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if (text == null) {
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throw new IllegalArgumentException("text is null");
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}
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if (paragraphLength < 0) {
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throw new IllegalArgumentException("bad length: " + paragraphLength);
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}
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if (textStart < 0 || paragraphLength > text.length - textStart) {
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throw new IllegalArgumentException("bad range: " + textStart +
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" length: " + paragraphLength +
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" for text of length: " + text.length);
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}
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if (embeddings != null && (embStart < 0 || paragraphLength > embeddings.length - embStart)) {
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throw new IllegalArgumentException("bad range: " + embStart +
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" length: " + paragraphLength +
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" for embeddings of length: " + text.length);
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}
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bidiBase = new BidiBase(text, textStart, embeddings, embStart, paragraphLength, flags);
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}
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/**
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* Create a Bidi object representing the bidi information on a line of text within
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* the paragraph represented by the current Bidi. This call is not required if the
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* entire paragraph fits on one line.
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*
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* @param lineStart the offset from the start of the paragraph to the start of the line.
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* @param lineLimit the offset from the start of the paragraph to the limit of the line.
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* @return a {@code Bidi} object
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*/
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public Bidi createLineBidi(int lineStart, int lineLimit) {
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AttributedString astr = new AttributedString("");
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Bidi newBidi = new Bidi(astr.getIterator());
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return bidiBase.setLine(this, bidiBase, newBidi, newBidi.bidiBase,lineStart, lineLimit);
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}
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/**
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* Return true if the line is not left-to-right or right-to-left. This means it either has mixed runs of left-to-right
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* and right-to-left text, or the base direction differs from the direction of the only run of text.
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*
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* @return true if the line is not left-to-right or right-to-left.
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*/
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public boolean isMixed() {
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return bidiBase.isMixed();
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}
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/**
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* Return true if the line is all left-to-right text and the base direction is left-to-right.
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*
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* @return true if the line is all left-to-right text and the base direction is left-to-right
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*/
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public boolean isLeftToRight() {
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return bidiBase.isLeftToRight();
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}
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/**
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* Return true if the line is all right-to-left text, and the base direction is right-to-left.
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* @return true if the line is all right-to-left text, and the base direction is right-to-left
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*/
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public boolean isRightToLeft() {
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return bidiBase.isRightToLeft();
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}
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/**
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* Return the length of text in the line.
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* @return the length of text in the line
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*/
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public int getLength() {
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return bidiBase.getLength();
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}
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/**
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* Return true if the base direction is left-to-right.
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* @return true if the base direction is left-to-right
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*/
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public boolean baseIsLeftToRight() {
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return bidiBase.baseIsLeftToRight();
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}
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/**
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* Return the base level (0 if left-to-right, 1 if right-to-left).
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* @return the base level
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*/
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public int getBaseLevel() {
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return bidiBase.getParaLevel();
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}
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/**
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* Return the resolved level of the character at offset. If offset is
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* {@literal <} 0 or ≥ the length of the line, return the base direction
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* level.
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*
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* @param offset the index of the character for which to return the level
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* @return the resolved level of the character at offset
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*/
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public int getLevelAt(int offset) {
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return bidiBase.getLevelAt(offset);
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}
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/**
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* Return the number of level runs.
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* @return the number of level runs
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*/
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public int getRunCount() {
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return bidiBase.countRuns();
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}
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/**
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* Return the level of the nth logical run in this line.
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* @param run the index of the run, between 0 and <code>getRunCount()</code>
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* @return the level of the run
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*/
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public int getRunLevel(int run) {
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return bidiBase.getRunLevel(run);
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}
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/**
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* Return the index of the character at the start of the nth logical run in this line, as
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* an offset from the start of the line.
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* @param run the index of the run, between 0 and <code>getRunCount()</code>
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* @return the start of the run
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*/
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public int getRunStart(int run) {
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return bidiBase.getRunStart(run);
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}
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/**
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* Return the index of the character past the end of the nth logical run in this line, as
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* an offset from the start of the line. For example, this will return the length
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* of the line for the last run on the line.
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* @param run the index of the run, between 0 and <code>getRunCount()</code>
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* @return limit the limit of the run
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*/
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public int getRunLimit(int run) {
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return bidiBase.getRunLimit(run);
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}
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/**
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* Return true if the specified text requires bidi analysis. If this returns false,
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* the text will display left-to-right. Clients can then avoid constructing a Bidi object.
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* Text in the Arabic Presentation Forms area of Unicode is presumed to already be shaped
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* and ordered for display, and so will not cause this function to return true.
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*
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* @param text the text containing the characters to test
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* @param start the start of the range of characters to test
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* @param limit the limit of the range of characters to test
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* @return true if the range of characters requires bidi analysis
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*/
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public static boolean requiresBidi(char[] text, int start, int limit) {
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return BidiBase.requiresBidi(text, start, limit);
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}
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/**
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* Reorder the objects in the array into visual order based on their levels.
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* This is a utility function to use when you have a collection of objects
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* representing runs of text in logical order, each run containing text
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* at a single level. The elements at <code>index</code> from
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* <code>objectStart</code> up to <code>objectStart + count</code>
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* in the objects array will be reordered into visual order assuming
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* each run of text has the level indicated by the corresponding element
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* in the levels array (at <code>index - objectStart + levelStart</code>).
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*
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* @param levels an array representing the bidi level of each object
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* @param levelStart the start position in the levels array
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* @param objects the array of objects to be reordered into visual order
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* @param objectStart the start position in the objects array
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* @param count the number of objects to reorder
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*/
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public static void reorderVisually(byte[] levels, int levelStart, Object[] objects, int objectStart, int count) {
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BidiBase.reorderVisually(levels, levelStart, objects, objectStart, count);
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}
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/**
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* Display the bidi internal state, used in debugging.
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*/
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public String toString() {
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return bidiBase.toString();
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}
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}
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