awt/java/awt/font/TextMeasurer.java

/*
 *  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.
 */
/*
 * @author Oleg V. Khaschansky
 * @version $Revision$
 */

package java.awt.font;


import java.text.AttributedCharacterIterator;

import org.apache.harmony.awt.gl.font.TextMetricsCalculator;
import org.apache.harmony.awt.gl.font.TextRunBreaker;

/**
 * The TextMeasurer class provides utilities for line break operations.
 */
public final class TextMeasurer implements Cloneable {
    
    /** The aci. */
    AttributedCharacterIterator aci;
    
    /** The frc. */
    FontRenderContext frc;
    
    /** The breaker. */
    TextRunBreaker breaker = null;
    
    /** The tmc. */
    TextMetricsCalculator tmc = null;

    /**
     * Instantiates a new text measurer from the specified text.
     * 
     * @param text the source text.
     * @param frc the FontRenderContext.
     */
    public TextMeasurer(AttributedCharacterIterator text, FontRenderContext frc) {
        this.aci = text;
        this.frc = frc;
        breaker = new TextRunBreaker(aci, this.frc);
        tmc = new TextMetricsCalculator(breaker);
    }

    /**
     * Replaces the current text with the new text, inserting a break
     * character at the specified insert position.  
     * 
     * @param newParagraph the new paragraph text. 
     * @param insertPos the position in the text where the character is inserted. 
     */
    public void insertChar(AttributedCharacterIterator newParagraph, int insertPos) {
        AttributedCharacterIterator oldAci = aci;
        aci = newParagraph;
        if ((oldAci.getEndIndex() - oldAci.getBeginIndex()) -
           (aci.getEndIndex() - aci.getBeginIndex()) != -1) {
            breaker = new TextRunBreaker(aci, this.frc);
            tmc = new TextMetricsCalculator(breaker);
        } else {
            breaker.insertChar(newParagraph, insertPos);
        }
    }

    /**
     * Replaces the current text with the new text and deletes a
     * character at the specified position.  
     * 
     * @param newParagraph the paragraph text after deletion. 
     * @param deletePos the position in the text where the character is removed. 
     */
    public void deleteChar(AttributedCharacterIterator newParagraph, int deletePos) {
        AttributedCharacterIterator oldAci = aci;
        aci = newParagraph;
        if ((oldAci.getEndIndex() - oldAci.getBeginIndex()) -
           (aci.getEndIndex() - aci.getBeginIndex()) != 1) {
            breaker = new TextRunBreaker(aci, this.frc);
            tmc = new TextMetricsCalculator(breaker);
        } else {
            breaker.deleteChar(newParagraph, deletePos);
        }
    }

    /**
     * Returns a copy of this object.
     * 
     * @return a copy of this object.
     */
    @Override
    protected Object clone() {
        return new TextMeasurer((AttributedCharacterIterator) aci.clone(), frc);
    }

    /**
     * Returns a TextLayout of the specified character range.
     * 
     * @param start the index of the first character.
     * @param limit the index after the last character. 
     * 
     * @return a TextLayout for the characters beginning at "start" up 
     * to "end".
     */
    public TextLayout getLayout(int start, int limit) {
        breaker.pushSegments(start - aci.getBeginIndex(), limit - aci.getBeginIndex());

        breaker.createAllSegments();
        TextLayout layout = new TextLayout((TextRunBreaker) breaker.clone());

        breaker.popSegments();
        return layout;
    }

    /**
     * Returns the graphical width of a line beginning at "start" 
     * parameter and including characters up to "end" parameter. 
     * "start" and "end" are absolute indices, not relative to the 
     * "start" of the paragraph.
     * 
     * @param start the character index at which to start measuring.
     * @param end the character index at which to stop measuring.
     * 
     * @return the graphical width of a line beginning at "start"  
     * and including characters up to "end".
     */
    public float getAdvanceBetween(int start, int end) {
        breaker.pushSegments(start - aci.getBeginIndex(), end - aci.getBeginIndex());

        breaker.createAllSegments();
        float retval = tmc.createMetrics().getAdvance();

        breaker.popSegments();
        return retval;
    }

    /**
     * Returns the index of the first character which is not fit on 
     * a line beginning at start and possible measuring up to maxAdvance 
     * in graphical width.
     * 
     * @param start he character index at which to start measuring. 
     * @param maxAdvance the graphical width in which the line must fit. 
     * 
     * @return the index after the last character that is fit on a line 
     * beginning at start, which is not longer than maxAdvance in graphical
     * width.
     */
    public int getLineBreakIndex(int start, float maxAdvance) {
        breaker.createAllSegments();
        return breaker.getLineBreakIndex(
                start - aci.getBeginIndex(), maxAdvance) + aci.getBeginIndex();
    }
}