src/com/ibm/richtext/styledtext/StyleModifier.java

/*
 * (C) Copyright IBM Corp. 1998-2004.  All Rights Reserved.
 *
 * The program is provided "as is" without any warranty express or
 * implied, including the warranty of non-infringement and the implied
 * warranties of merchantibility and fitness for a particular purpose.
 * IBM will not be liable for any damages suffered by you as a result
 * of using the Program. In no event will IBM be liable for any
 * special, indirect or consequential damages or lost profits even if
 * IBM has been advised of the possibility of their occurrence. IBM
 * will not be liable for any third party claims against you.
 */
package com.ibm.richtext.styledtext;

import com.ibm.richtext.textlayout.attributes.AttributeMap;
import com.ibm.richtext.textlayout.attributes.AttributeSet;

/**
 * StyleModifier is the base class for operations on AttributeMap.  To implement
 * an operation on AttributeMap, subclass StyleModifier and override
 * <code>modifyStyle</code>.  StyleModifiers are used by MText.
 * <p>
 * For convenience, this class contains factory methods which will create a
 * StyleModifier for
 * certain common operations: attribute union, attribute removal, and AttributeMap
 * replacement.
 * @see AttributeMap
 * @see AttributeSet
 * @see MText
 */
/*
 * {jbr} StyleModifier is not the best name for this class - styles are immutable and never
 * really modified.
 */
public class StyleModifier
{
    static final String COPYRIGHT =
                "(C) Copyright IBM Corp. 1998-1999 - All Rights Reserved";
    /**
     * Create a StyleModifier.
     */
    protected StyleModifier() {
    }

    /**
     * Return the result of this StyleModifier's operation on the given style.
     * Default implementation just returns the given style.
     * @param style the AttributeMap to perform the operation on
     */
    public AttributeMap modifyStyle(AttributeMap style)
    {
        return style;
    }

    /**
     * A StyleModifier which simply returns the given style.
     */
    public static final StyleModifier IDENTITY = new StyleModifier();

    /**
     * Create a StyleModifier whose operation is
     * <code>style.addAttributes(s)</code>,
     * where <code>style</code> is the AttributeMap passed to
     * <code>modifyStyle</code>.
     * @param s the AttributeMap to union with
     * @return a StyleModifier for this operation
     */
    public static StyleModifier createAddModifier(AttributeMap s) {

        return new StyleAddModifier(s);
    }

    /**
     * Create a StyleModifier whose operation is
     * <code>style.addAttribute(key, value)</code>,
     * where <code>style</code> is the AttributeMap passed to
     * <code>modifyStyle</code>.
     * @param key the key to add
     * @param value the value to add
     * @return a StyleModifier for this operation
     */
    public static StyleModifier createAddModifier(Object key,
                                                  Object value) {

        return new AttributeAddModifier(key, value);
    }

    /**
     * Create a StyleModifier whose operation returns <code>s</code>,
     * ignoring the parameter to <code>modifyStyle</code>.
     * @param s the AttributeMap which will replace any other AttributeMap
     * @return a StyleModifier for this operation
     */
    public static StyleModifier createReplaceModifier(AttributeMap s) {

        return new StyleReplaceModifier(s);
    }

    /**
     * Create a StyleModifier whose operation is
     * <code>style.removeAttributes(s)</code>,
     * where <code>style</code> is the AttributeMap passed to
     * <code>modifyStyle</code>.
     * @param s the AttributeSet of attributes to remove
     * @return a StyleModifier for this operation
     */
    public static StyleModifier createRemoveModifier(AttributeSet s) {

        return new StyleRemoveModifier(s);
    }

    static final class AttributeAddModifier extends StyleModifier {

        private Object fKey;
        private Object fValue;

        public AttributeAddModifier(Object key, Object value) {

            fKey = key;
            fValue = value;
        }

        public AttributeMap modifyStyle(AttributeMap style) {

            return style.addAttribute(fKey, fValue);
        }
    }

    /**
     * Create this with the styles to add.  These styles will add to and override any already
     * present in the style passed to modifyStyle.
     */
    static final class StyleAddModifier extends StyleModifier
    {
        private AttributeMap fStyle;

        public StyleAddModifier(AttributeMap style)
        {
            if (style == null) {
                throw new IllegalArgumentException("style is null");
            }
            fStyle = style;
        }

        public AttributeMap modifyStyle(AttributeMap style)
        {
            return style.addAttributes(fStyle);
        }
    }

    /**
     * Create this with the styles to replace.  All style runs will have only these
     * styles.
     */
    static final class StyleReplaceModifier extends StyleModifier
    {
        private AttributeMap fStyle;

        public StyleReplaceModifier(AttributeMap style)
        {
            if (style == null) {
                throw new IllegalArgumentException("style is null");
            }
            fStyle = style;
        }

        public AttributeMap modifyStyle(AttributeMap style)
        {
            return fStyle;
        }
    }

    static final class StyleRemoveModifier extends StyleModifier {

        private AttributeSet fRemoveSet;

        public StyleRemoveModifier(AttributeSet removeSet) {

            if (removeSet == null) {
                throw new IllegalArgumentException("set is null");
            }
            fRemoveSet = removeSet;
        }

        public AttributeMap modifyStyle(AttributeMap style) {

            return style.removeAttributes(fRemoveSet);
        }
    }
}