nullgraphics.java

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/*
 * @(#)NullGraphics.java	1.13 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
 * 
 * This program 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. 
 * 
 * This program 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 at /legal/license.txt). 
 * 
 * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa
 * Clara, CA 95054 or visit www.sun.com if you need additional
 * information or have any questions. 
 *
 */

package sun.awt;

import java.awt.*;
import java.awt.image.ImageObserver;
import java.text.AttributedCharacterIterator;

/**
 A Graphics object which ignores all draw requests. This is useful
 to ensure that a displayable, but not visible, component can get a graphics
 object to draw onto without drawing onto the screen.
 @author Nicholas Allen
 @version 1.7, 08/19/02
 */

public class NullGraphics extends Graphics {
    private Color color;
    private Rectangle clipBounds;
    private Font font;
    public NullGraphics(Component component) {
        color = component.getForeground();
        if (color == null)
            color = Color.black;
        font = component.getFont();
        if (font == null)
            font = new Font("dialog", Font.PLAIN, 12);
    }
	
    private NullGraphics(NullGraphics g) {
        color = g.color;
        font = g.font;
        clipBounds = g.clipBounds;
    }

    /**
     * Creates a new <code>Graphics</code> object that is
     * a copy of this <code>Graphics</code> object.
     * @return     a new graphics context that is a copy of
     *                       this graphics context.
     * @since      JDK1.0
     */
    public Graphics create() {
        return new NullGraphics(this);
    }

    /**
     * Translates the origin of the graphics context to the point
     * (<i>x</i>,&nbsp;<i>y</i>) in the current coordinate system.
     * Modifies this graphics context so that its new origin corresponds
     * to the point (<i>x</i>,&nbsp;<i>y</i>) in this graphics context's
     * original coordinate system.  All coordinates used in subsequent
     * rendering operations on this graphics context will be relative
     * to this new origin.
     * @param  x   the <i>x</i> coordinate.
     * @param  y   the <i>y</i> coordinate.
     * @since   JDK1.0
     */
    public void translate(int x, int y) {
        if (clipBounds != null) {
            clipBounds.x -= x;
            clipBounds.y -= y;
        }
    }

    /**
     * Gets this graphics context's current color.
     * @return    this graphics context's current color.
     * @see       java.awt.Color
     * @see       java.awt.Graphics#setColor
     * @since     JDK1.0
     */
    public Color getColor() {
        return color;
    }

    /**
     * Sets this graphics context's current color to the specified
     * color. All subsequent graphics operations using this graphics
     * context use this specified color.
     * @param     c   the new rendering color.
     * @see       java.awt.Color
     * @see       java.awt.Graphics#getColor
     * @since     JDK1.0
     */
    public void setColor(Color c) {
        if (c == null)
            color = Color.black;
        else color = c;
    }

    /**
     * Sets the paint mode of this graphics context to overwrite the
     * destination with this graphics context's current color.
     * This sets the logical pixel operation function to the paint or
     * overwrite mode.  All subsequent rendering operations will
     * overwrite the destination with the current color.
     * @since   JDK1.0
     */
    public void setPaintMode() {}

    /**
     * This method sets the graphics context to xor paint mode using
     * the "exclusive or"  color xorcolor.
     * This specifies that logical pixel operations are performed in the
     * XOR mode, which alternates pixels between the current color and
     * a specified XOR color.
     * <p>
     * When drawing operations are performed, pixels which are the
     * current color are changed to the specified color, and vice versa.
     * <p>
     * Pixels that are of colors other than those two colors are changed
     * in an unpredictable but reversible manner; if the same figure is
     * drawn twice, then all pixels are restored to their original values.
     * <h3>Compatibility</h3>
     * Both PersonalJava and Personal Profile implementations are not required
     * to support this method.
     * <h3>System Properties</h3>
     * The System Property <code>java.awt.graphics.SupportsXorMode</code> is set to
     * <code>"true"</code> or <code>"false"</code> indicating if the platform supports
     * XOR rendering.
     * @param     c1 the XOR alternation color
     * @exception <code>UnsupportedOperationException</code> if the implementation does
     *             not support an XOR paint mode.
     * @since     JDK1.0
     */
    public void setXORMode(Color c1) {}

    /**
     * Gets the current font.
     * @return    this graphics context's current font.
     * @see       java.awt.Font
     * @see       java.awt.Graphics#setFont
     * @since     JDK1.0
     */
    public Font getFont() {
        return font;
    }

    /**
     * Sets this graphics context's font to the specified font.
     * All subsequent text operations using this graphics context
     * use this font.
     * @param  font   the font.
     * @see     java.awt.Graphics#getFont
     * @see     java.awt.Graphics#drawChars
     * @see     java.awt.Graphics#drawString
     * @see     java.awt.Graphics#drawBytes
     * @since   JDK1.0
     */
    public void setFont(Font font) {
        this.font = font;
    }

    /**
     * Gets the font metrics for the specified font.
     * @return    the font metrics for the specified font.
     * @param     f the specified font
     * @see       java.awt.Graphics#getFont
     * @see       java.awt.FontMetrics
     * @see       java.awt.Graphics#getFontMetrics()
     * @since     JDK1.0
     */
    public FontMetrics getFontMetrics(Font f) {
        return Toolkit.getDefaultToolkit().getFontMetrics(f);
    }

    /**
     * Returns the bounding rectangle of the current clipping area.
     * The coordinates in the rectangle are relative to the coordinate
     * system origin of this graphics context.
     * @return      the bounding rectangle of the current clipping area.
     * @see         java.awt.Graphics#getClip
     * @see         java.awt.Graphics#clipRect
     * @see         java.awt.Graphics#setClip(int, int, int, int)
     * @see         java.awt.Graphics#setClip(Shape)
     * @since       JDK1.1
     */
    public Rectangle getClipBounds() {
        return clipBounds;
    }

    /**
     * Intersects the current clip with the specified rectangle.
     * The resulting clipping area is the intersection of the current
     * clipping area and the specified rectangle.
     * This method can only be used to make the current clip smaller.
     * To set the current clip larger, use any of the setClip methods.
     * Rendering operations have no effect outside of the clipping area.
     * @param x the x coordinate of the rectangle to intersect the clip with
     * @param y the y coordinate of the rectangle to intersect the clip with
     * @param width the width of the rectangle to intersect the clip with
     * @param height the height of the rectangle to intersect the clip with
     * @see #setClip(int, int, int, int)
     * @see #setClip(Shape)
     */
    public void clipRect(int x, int y, int width, int height) {
        Rectangle rect = new Rectangle(x, y, width, height);
        if (clipBounds == null)
            clipBounds = rect;
        else clipBounds = clipBounds.union(rect);
    }

    /**
     * Sets the current clip to the rectangle specified by the given
     * coordinates.
     * Rendering operations have no effect outside of the clipping area.
     * @param       x the <i>x</i> coordinate of the new clip rectangle.
     * @param       y the <i>y</i> coordinate of the new clip rectangle.
     * @param       width the width of the new clip rectangle.
     * @param       height the height of the new clip rectangle.
     * @see         java.awt.Graphics#clipRect
     * @see         java.awt.Graphics#setClip(Shape)
     * @since       JDK1.1
     */
    public void setClip(int x, int y, int width, int height) {
        clipBounds = new Rectangle(x, y, width, height);
    }

    /**
     * Gets the current clipping area.
     * @return      a <code>Shape</code> object representing the
     *                      current clipping area.
     * @see         java.awt.Graphics#getClipBounds
     * @see         java.awt.Graphics#clipRect
     * @see         java.awt.Graphics#setClip(int, int, int, int)
     * @see         java.awt.Graphics#setClip(Shape)
     * @since       JDK1.1
     */
    public Shape getClip() {
        return clipBounds;
    }

    /**
     * Sets the current clipping area to an arbitrary clip shape.
     * Not all objects which implement the <code>Shape</code>
     * interface can be used to set the clip.  The only
     * <code>Shape</code> objects which are guaranteed to be
     * supported are <code>Shape</code> objects which are
     * obtained via the <code>getClip</code> method and via
     * <code>Rectangle</code> objects.
     * @see         java.awt.Graphics#getClip()
     * @see         java.awt.Graphics#clipRect
     * @see         java.awt.Graphics#setClip(int, int, int, int)
     * @since       JDK1.1
     */
    public void setClip(Shape clip) {
        if (!(clip instanceof Rectangle))
            throw new AWTError("Only rectangular clip regions supported");
        clipBounds = (Rectangle) clip;
    }

    /**
     * Copies an area of the component by a distance specified by
     * <code>dx</code> and <code>dy</code>. From the point specified
     * by <code>x</code> and <code>y</code>, this method
     * copies downwards and to the right.  To copy an area of the
     * component to the left or upwards, specify a negative value for
     * <code>dx</code> or <code>dy</code>.
     * If a portion of the source rectangle lies outside the bounds
     * of the component, or is obscured by another window or component,
     * <code>copyArea</code> will be unable to copy the associated
     * pixels. The area that is omitted can be refreshed by calling
     * the component's <code>paint</code> method.
     * @param       x the <i>x</i> coordinate of the source rectangle.
     * @param       y the <i>y</i> coordinate of the source rectangle.
     * @param       width the width of the source rectangle.
     * @param       height the height of the source rectangle.
     * @param       dx the horizontal distance to copy the pixels.
     * @param       dy the vertical distance to copy the pixels.
     * @since       JDK1.0
     */
    public void copyArea(int x, int y, int width, int height,
        int dx, int dy) {}

    /**
     * Draws a line, using the current color, between the points
     * <code>(x1,&nbsp;y1)</code> and <code>(x2,&nbsp;y2)</code>
     * in this graphics context's coordinate system.
     * @param   x1  the first point's <i>x</i> coordinate.
     * @param   y1  the first point's <i>y</i> coordinate.
     * @param   x2  the second point's <i>x</i> coordinate.
     * @param   y2  the second point's <i>y</i> coordinate.
     * @since   JDK1.0
     */
    public void drawLine(int x1, int y1, int x2, int y2) {}

    /**
     * Fills the specified rectangle.
     * The left and right edges of the rectangle are at
     * <code>x</code> and <code>x&nbsp;+&nbsp;width&nbsp;-&nbsp;1</code>.
     * The top and bottom edges are at
     * <code>y</code> and <code>y&nbsp;+&nbsp;height&nbsp;-&nbsp;1</code>.
     * The resulting rectangle covers an area
     * <code>width</code> pixels wide by
     * <code>height</code> pixels tall.
     * The rectangle is filled using the graphics context's current color.
     * @param         x   the <i>x</i> coordinate
     *                         of the rectangle to be filled.
     * @param         y   the <i>y</i> coordinate
     *                         of the rectangle to be filled.
     * @param         width   the width of the rectangle to be filled.