Java Swing Text Style getNextVisualPosition(final View v, final int pos, final Position.Bias b0, final int direction, final Position.Bias[] biasRet)

Description

get Next Visual Position

License

Apache License

Declaration

private static int getNextVisualPosition(final View v, final int pos, final Position.Bias b0,
            final int direction, final Position.Bias[] biasRet) 

Method Source Code

//package com.java2s;
/*/*from  w ww .ja  v a2 s.co  m*/
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

import javax.swing.SwingConstants;
import javax.swing.text.AbstractDocument;

import javax.swing.text.Document;
import javax.swing.text.Element;

import javax.swing.text.Position;

import javax.swing.text.StyleConstants;

import javax.swing.text.View;

public class Main {
    static final Position.Bias backward = Position.Bias.Backward;
    static final Position.Bias forward = Position.Bias.Forward;

    private static int getNextVisualPosition(final View v, final int pos, final Position.Bias b0,
            final int direction, final Position.Bias[] biasRet) {
        boolean toWest = (direction == SwingConstants.WEST);
        Document document = v.getDocument();
        int length = document.getLength();
        if (!isBidirectional(document)) {
            return getTrivialVisualPosition(toWest, pos, b0, length, biasRet, true);
        }
        Element bidiRoot = ((AbstractDocument) document).getBidiRootElement();
        Element elem = getElementByPosition(bidiRoot, pos);
        boolean isLTR = isLTR(elem);
        int start = elem.getStartOffset();
        int end = elem.getEndOffset() - 1;

        int posInNeighboringElement = toWest ? Math.max(start - 1, 0) : Math.min(end + 1, length);
        Element neighboringElement = getElementByPosition(bidiRoot, posInNeighboringElement);

        Element paragraph = getElementByPosition(document.getDefaultRootElement(), pos);
        int startParagraph = paragraph.getStartOffset();
        int endParagraph = paragraph.getEndOffset() - 1;

        boolean nextIsLTR = isLTR(getElementByPosition(bidiRoot, Math.min(endParagraph + 1, length)));

        int result = checkBoundaryCondition(pos, b0, biasRet, neighboringElement, isLTR, toWest, start, length,
                startParagraph, endParagraph, nextIsLTR);

        return result >= 0 ? result
                : getBidiVisualPosition(start, end, neighboringElement, pos, b0, biasRet, length, toWest, isLTR);
    }

    public static final boolean isBidirectional(final Document document) {
        if (!(document instanceof AbstractDocument)) {
            return false;
        }
        Element bidiRoot = ((AbstractDocument) document).getBidiRootElement();
        return (bidiRoot != null && bidiRoot.getElementCount() >= 2);
    }

    private static int getTrivialVisualPosition(final boolean toWest, final int pos, final Position.Bias bias,
            final int docLength, final Position.Bias[] biasRet, final boolean isLTR) {
        boolean condition = (toWest && isLTR) || (!toWest && !isLTR);
        return condition ? Math.max(pos - 1, 0) : Math.min(pos + 1, docLength);
    }

    private static Element getElementByPosition(final Element rootElement, final int pos) {
        int index = rootElement.getElementIndex(pos);
        return rootElement.getElement(index);
    }

    static final boolean isLTR(final Element element) {
        return isLTR(StyleConstants.getBidiLevel(element.getAttributes()));
    }

    public static final boolean isLTR(final int level) {
        return (level & 1) == 0;
    }

    private static int checkBoundaryCondition(final int pos, final Position.Bias b0, final Position.Bias[] biasRet,
            final Element neighboringElement, final boolean isLTR, final boolean toWest, final int start,
            final int length, final int startParagraph, final int endParagraph, final boolean nextIsLTR) {

        if (toWest && isLTR) {
            if (pos == startParagraph) {
                return Math.max(0, pos - 1);
            } else if (neighboringElement.getStartOffset() == startParagraph && pos == start && b0 == backward) {
                return Math.max(0, startParagraph - 1);
            }
        } else if (!toWest) {
            if (b0 == forward && pos == length) {
                biasRet[0] = b0;
                return pos;
            }
            if (b0 == forward && pos == endParagraph) {
                if (nextIsLTR) {
                    return pos + 1;
                }
                biasRet[0] = backward;
                return neighboringElement.getEndOffset();
            }
        }
        return -1;
    }

    static final int getBidiVisualPosition(final int start, final int end, final Element neighbouringElement,
            final int pos, final Position.Bias b0, final Position.Bias[] biasRet, final int length,
            final boolean toWest, final boolean isLTR) {
        boolean direction = toWest ^ isLTR;
        if (pos == end && direction && b0 == forward) {
            biasRet[0] = backward;
            return pos + 1;
        } else if (pos == start + 1 && pos <= end && !direction) {
            return pos - 1;
        } else if (pos == start) {
            if (direction) {
                return (b0 == forward) ? pos + 1 : pos - 1;
            }
            biasRet[0] = b0;
            return neighbouringElement.getStartOffset();
        } else {
            return getTrivialVisualPosition(toWest, pos, b0, length, biasRet, isLTR);
        }
    }
}

Related

1. createStyle(String logicalName)
2. getBooleanValue(Element element, Object constant)
3. getIntegerValue(Element element, Object constant)
4. hasDifferentCharacterAttributes(AttributeSet style, AttributeSet base)
5. isCentered(AttributeSet attributes)
6. isLTR(final int level)
7. overrideStyle(Style originalStyle, Style newStyle)