ImageBackgroundPainterStrategy.java

/*
 * 01/22/2005
 *
 * ImageBackgroundPainterStrategy.java - Renders an RTextAreaBase's
 * background as an image.
 * Copyright (C) 2005 Robert Futrell
 * robert_futrell at users.sourceforge.net
 * http://fifesoft.com/rsyntaxtextarea
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA.
 */
package org.fife.ui.rtextarea;

import java.awt.Graphics;
import java.awt.Image;
import java.awt.MediaTracker;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.net.URL;
import javax.imageio.ImageIO;

/**
 * A strategy for painting the background of an <code>RTextAreaBase</code> as an image. The image is always stretched to
 * completely fill the <code>RTextAreaBase</code>.
 * <p>
 * 
 * You can set the scaling hint used when stretching/skewing the image to fit in the <code>RTextAreaBase</code>'s
 * background via the <code>setScalingHint</code> method, but keep in mind the more accurate the scaling hint, the less
 * responsive your application will be when stretching the window (as that's the only time the image's size is
 * recalculated).
 * 
 * @author Robert Futrell
 * @version 0.1
 * @see org.fife.ui.rtextarea.BufferedImageBackgroundPainterStrategy
 * @see org.fife.ui.rtextarea.VolatileImageBackgroundPainterStrategy
 */
public abstract class ImageBackgroundPainterStrategy
        implements BackgroundPainterStrategy {

    protected MediaTracker tracker;

    private RTextAreaBase textArea;
    private Image master;
    private int oldWidth, oldHeight;
    private int scalingHint;

    /**
     * Constructor.
     * 
     * @param textArea
     *            The text area using this image as its background.
     */
    public ImageBackgroundPainterStrategy(RTextAreaBase textArea) {
        this.textArea = textArea;
        tracker = new MediaTracker(textArea);
        scalingHint = Image.SCALE_FAST;
    }

    /**
     * Returns the text area using this strategy.
     * 
     * @return The text area.
     */
    public RTextAreaBase getRTextAreaBase() {
        return textArea;
    }

    /**
     * Returns the "master" image; that is, the original, unscaled image. When the image needs to be rescaled, scaling
     * should be done from this image, to prevent repeated scaling from distorting the image.
     * 
     * @return The master image.
     */
    public Image getMasterImage() {
        return master;
    }

    /**
     * Returns the scaling hint being used.
     * 
     * @return The scaling hint to use when scaling an image.
     * @see #setScalingHint
     */
    public int getScalingHint() {
        return scalingHint;
    }

    /**
     * Paints the image at the specified location and at the specified size.
     * 
     * @param g
     *            The graphics context.
     * @param bounds
     *            The bounds in which to paint the image. The image will be scaled to fit exactly in these bounds if
     *            necessary.
     */
    public final void paint(Graphics g, Rectangle bounds) {
        if (bounds.width != oldWidth || bounds.height != oldHeight) {
            rescaleImage(bounds.width, bounds.height, getScalingHint());
            oldWidth = bounds.width;
            oldHeight = bounds.height;
        }
        paintImage(g, bounds.x, bounds.y);
    }

    /**
     * Paints the image at the specified location. This method assumes scaling has already been done, and simply paints
     * the background image "as-is."
     * 
     * @param g
     *            The graphics context.
     * @param x
     *            The x-coordinate at which to paint.
     * @param y
     *            The y-coordinate at which to paint.
     */
    protected abstract void paintImage(Graphics g, int x, int y);

    /**
     * Rescales the displayed image to be the specified size.
     * 
     * @param width
     *            The new width of the image.
     * @param height
     *            The new height of the image.
     * @param hint
     *            The scaling hint to use.
     */
    protected abstract void rescaleImage(int width, int height,
            int hint);

    /**
     * Sets the image this background painter displays.
     * 
     * @param imageURL
     *            URL of a file containing the image to display.
     */
    public void setImage(URL imageURL) {
        BufferedImage image = null;
        try {
            image = ImageIO.read(imageURL);
        } catch (Exception e) {
            e.printStackTrace();
        }
        setImage(image);
    }

    /**
     * Sets the image this background painter displays.
     * 
     * @param image
     *            The new image to use for the background.
     */
    public void setImage(Image image) {
        master = image;
        oldWidth = -1; // To trick us into fixing bgImage.
    }

    /**
     * Sets the scaling hint to use when scaling the image.
     * 
     * @param hint
     *            The hint to apply; e.g. <code>Image.SCALE_DEFAULT</code>.
     * @see #getScalingHint
     */
    public void setScalingHint(int hint) {
        this.scalingHint = hint;
    }

}