JDK8/Java8源码在线阅读

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */
package javax.swing.text;

import java.awt.*;
import javax.swing.event.*;

/**
 * A <code>LabelView</code> is a styled chunk of text
 * that represents a view mapped over an element in the
 * text model.  It caches the character level attributes
 * used for rendering.
 *
 * @author Timothy Prinzing
 */
public class LabelView extends GlyphView implements TabableView {

    /**
     * Constructs a new view wrapped on an element.
     *
     * @param elem the element
     */
    public LabelView(Element elem) {
        super(elem);
    }

    /**
     * Synchronize the view's cached values with the model.
     * This causes the font, metrics, color, etc to be
     * re-cached if the cache has been invalidated.
     */
    final void sync() {
        if (font == null) {
            setPropertiesFromAttributes();
        }
    }

    /**
     * Sets whether or not the view is underlined.
     * Note that this setter is protected and is really
     * only meant if you need to update some additional
     * state when set.
     *
     * @param u true if the view is underlined, otherwise
     *          false
     * @see #isUnderline
     */
    protected void setUnderline(boolean u) {
        underline = u;
    }

    /**
     * Sets whether or not the view has a strike/line
     * through it.
     * Note that this setter is protected and is really
     * only meant if you need to update some additional
     * state when set.
     *
     * @param s true if the view has a strike/line
     *          through it, otherwise false
     * @see #isStrikeThrough
     */
    protected void setStrikeThrough(boolean s) {
        strike = s;
    }


    /**
     * Sets whether or not the view represents a
     * superscript.
     * Note that this setter is protected and is really
     * only meant if you need to update some additional
     * state when set.
     *
     * @param s true if the view represents a
     *          superscript, otherwise false
     * @see #isSuperscript
     */
    protected void setSuperscript(boolean s) {
        superscript = s;
    }

    /**
     * Sets whether or not the view represents a
     * subscript.
     * Note that this setter is protected and is really
     * only meant if you need to update some additional
     * state when set.
     *
     * @param s true if the view represents a
     *          subscript, otherwise false
     * @see #isSubscript
     */
    protected void setSubscript(boolean s) {
        subscript = s;
    }

    /**
     * Sets the background color for the view. This method is typically
     * invoked as part of configuring this <code>View</code>. If you need
     * to customize the background color you should override
     * <code>setPropertiesFromAttributes</code> and invoke this method. A
     * value of null indicates no background should be rendered, so that the
     * background of the parent <code>View</code> will show through.
     *
     * @param bg background color, or null
     * @see #setPropertiesFromAttributes
     * @since 1.5
     */
    protected void setBackground(Color bg) {
        this.bg = bg;
    }

    /**
     * Sets the cached properties from the attributes.
     */
    protected void setPropertiesFromAttributes() {
        AttributeSet attr = getAttributes();
        if (attr != null) {
            Document d = getDocument();
            if (d instanceof StyledDocument) {
                StyledDocument doc = (StyledDocument) d;
                font = doc.getFont(attr);
                fg = doc.getForeground(attr);
                if (attr.isDefined(StyleConstants.Background)) {
                    bg = doc.getBackground(attr);
                } else {
                    bg = null;
                }
                setUnderline(StyleConstants.isUnderline(attr));
                setStrikeThrough(StyleConstants.isStrikeThrough(attr));
                setSuperscript(StyleConstants.isSuperscript(attr));
                setSubscript(StyleConstants.isSubscript(attr));
            } else {
                throw new StateInvariantError("LabelView needs StyledDocument");
            }
        }
     }

    /**
     * Fetches the <code>FontMetrics</code> used for this view.
     * @deprecated FontMetrics are not used for glyph rendering
     *  when running in the JDK.
     */
    @Deprecated
    protected FontMetrics getFontMetrics() {
        sync();
        Container c = getContainer();
        return (c != null) ? c.getFontMetrics(font) :
            Toolkit.getDefaultToolkit().getFontMetrics(font);
    }

    /**
     * Fetches the background color to use to render the glyphs.
     * This is implemented to return a cached background color,
     * which defaults to <code>null</code>.
     *
     * @return the cached background color
     * @since 1.3
     */
    public Color getBackground() {
        sync();
        return bg;
    }

    /**
     * Fetches the foreground color to use to render the glyphs.
     * This is implemented to return a cached foreground color,
     * which defaults to <code>null</code>.
     *
     * @return the cached foreground color
     * @since 1.3
     */
    public Color getForeground() {
        sync();
        return fg;
    }

    /**
     * Fetches the font that the glyphs should be based upon.
     * This is implemented to return a cached font.
     *
     * @return the cached font
     */
     public Font getFont() {
        sync();
        return font;
    }

    /**
     * Determines if the glyphs should be underlined.  If true,
     * an underline should be drawn through the baseline.  This
     * is implemented to return the cached underline property.
     *
     * <p>When you request this property, <code>LabelView</code>
     * re-syncs its state with the properties of the
     * <code>Element</code>'s <code>AttributeSet</code>.
     * If <code>Element</code>'s <code>AttributeSet</code>
     * does not have this property set, it will revert to false.
     *
     * @return the value of the cached
     *     <code>underline</code> property
     * @since 1.3
     */
    public boolean isUnderline() {
        sync();
        return underline;
    }

    /**
     * Determines if the glyphs should have a strikethrough
     * line.  If true, a line should be drawn through the center
     * of the glyphs.  This is implemented to return the
     * cached <code>strikeThrough</code> property.
     *
     * <p>When you request this property, <code>LabelView</code>
     * re-syncs its state with the properties of the
     * <code>Element</code>'s <code>AttributeSet</code>.
     * If <code>Element</code>'s <code>AttributeSet</code>
     * does not have this property set, it will revert to false.
     *
     * @return the value of the cached
     *     <code>strikeThrough</code> property
     * @since 1.3
     */
    public boolean isStrikeThrough() {
        sync();
        return strike;
    }

    /**
     * Determines if the glyphs should be rendered as superscript.
     * @return the value of the cached subscript property
     *
     * <p>When you request this property, <code>LabelView</code>
     * re-syncs its state with the properties of the
     * <code>Element</code>'s <code>AttributeSet</code>.
     * If <code>Element</code>'s <code>AttributeSet</code>
     * does not have this property set, it will revert to false.
     *
     * @return the value of the cached
     *     <code>subscript</code> property
     * @since 1.3
     */
    public boolean isSubscript() {
        sync();
        return subscript;
    }

    /**
     * Determines if the glyphs should be rendered as subscript.
     *
     * <p>When you request this property, <code>LabelView</code>
     * re-syncs its state with the properties of the
     * <code>Element</code>'s <code>AttributeSet</code>.
     * If <code>Element</code>'s <code>AttributeSet</code>
     * does not have this property set, it will revert to false.
     *

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