001 /*
002 * This file is part of muCommander, http://www.mucommander.com
003 * Copyright (C) 2002-2008 Maxence Bernard
004 *
005 * muCommander is free software; you can redistribute it and/or modify
006 * it under the terms of the GNU General Public License as published by
007 * the Free Software Foundation; either version 3 of the License, or
008 * (at your option) any later version.
009 *
010 * muCommander is distributed in the hope that it will be useful,
011 * but WITHOUT ANY WARRANTY; without even the implied warranty of
012 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
013 * GNU General Public License for more details.
014 *
015 * You should have received a copy of the GNU General Public License
016 * along with this program. If not, see <http://www.gnu.org/licenses/>.
017 */
018
019 package com.mucommander.file.icon;
020
021 import com.mucommander.file.AbstractFile;
022
023 import javax.swing.*;
024 import java.awt.*;
025
026 /**
027 * <code>CacheableFileIconProvider</code> is an interface to be implemented by file icon providers that wish to use
028 * some icon caching to improve performance. This interface is to be used in conjunction with {@link CachedFileIconProvider}
029 * to form a functional cached provider.
030 *
031 * @author Maxence Bernard
032 */
033 public interface CacheableFileIconProvider extends FileIconProvider {
034
035 /**
036 * Returns <code>true</code> if the icon cache can be used for the specified file and preferred resolution. This
037 * method allows the icon cache to be used only for certain types of files and/or preferred resolutions.
038 *
039 * <p>This method is called by {@link CachedFileIconProvider#getFileIcon(com.mucommander.file.AbstractFile, java.awt.Dimension)}
040 * each time an icon is requested. If <code>true</code> is returned, the icon cache will be looked up with
041 * {@link #lookupCache(com.mucommander.file.AbstractFile, java.awt.Dimension)} and if the cache did not return
042 * an icon, the icon will be be added to the cache with {@link #addToCache(com.mucommander.file.AbstractFile, javax.swing.Icon, java.awt.Dimension)}.
043 * <br/>
044 * On the other hand, if <code>false</code> is returned, {@link #getFileIcon(com.mucommander.file.AbstractFile, java.awt.Dimension)}
045 * will simply be called, without querying or adding to the cache.
046 *
047 * @param file the file for which to retrieve an icon
048 * @param preferredResolution the preferred resolution for the icon
049 * @return true if the icon cache can be used with the specified file
050 */
051 public abstract boolean isCacheable(AbstractFile file, Dimension preferredResolution);
052
053 /**
054 * This method is called by {@link CachedFileIconProvider#getFileIcon(com.mucommander.file.AbstractFile, java.awt.Dimension)}
055 * to perform a cache lookup and give implementations a chance to re-use a cached icon. If a non-null value is
056 * returned, the returned icon will be used.
057 * <br/>
058 * On the other hand, if <code>null</code> is returned, the icon will be fetched using {@link #getFileIcon(com.mucommander.file.AbstractFile, java.awt.Dimension)}
059 * followed by a call to {@link #addToCache(com.mucommander.file.AbstractFile, javax.swing.Icon,java.awt.Dimension)}
060 * to add the freshly-retrieved icon to the cache.
061 *
062 * <p>This method is called only if the prior call to {@link #isCacheable(com.mucommander.file.AbstractFile, java.awt.Dimension)}
063 * returned <code>true</code>.</p>.
064 *
065 * @param file the file for which to look for a previously cached icon
066 * @param preferredResolution the preferred resolution for the icon
067 * @return a cached icon to re-use, null if there is none
068 */
069 public abstract Icon lookupCache(AbstractFile file, Dimension preferredResolution);
070
071 /**
072 * This method is called by {@link CachedFileIconProvider#getFileIcon(com.mucommander.file.AbstractFile, java.awt.Dimension)}
073 * to give implementations a chance to cache an icon fetched with {@link #getFileIcon(com.mucommander.file.AbstractFile, java.awt.Dimension)}
074 * and have it returned later by {@link #lookupCache(com.mucommander.file.AbstractFile, java.awt.Dimension)}.
075 * <br/>
076 * There is no obligation for this method to cache the given icon, implementations may freely choose whether to
077 * cache certain icons only.
078 *
079 * <p>This method is called only if the prior call to {@link #isCacheable(com.mucommander.file.AbstractFile, java.awt.Dimension)}
080 * returned <code>true</code>.</p>.
081 *
082 * @param file the file that corresponds to the given icon
083 * @param icon the icon to add to the cache
084 * @param preferredResolution the preferred icon resolution that was originally requested
085 */
086 public abstract void addToCache(AbstractFile file, Icon icon, Dimension preferredResolution);
087
088 }