component.java

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     */
    public boolean isForegroundSet() {
        return (foreground != null);
     }

    /**
     * Gets the background color of this component.
     * @return This component's background color. If this component does
     * not have a background color, the background color of its parent
     * is returned.
     * @see java.awt.Component#setBackground(java.awt.Color)
     * @since JDK1.0
     */
    public Color getBackground() {
        Color background = this.background;
        if (background != null) {
            return background;
        }
        Container parent = this.parent;
        return (parent != null) ? parent.getBackground() : null;
    }

    /**
     * Sets the background color of this component.
     * @param c The color to become this component's color.
     *        If this parameter is null then this component will inherit
     *        the background color of its parent.
     * background color.
     * @see #getBackground
     * @since JDK1.0
     */
    public void setBackground(Color c) {
	Color oldColor = background;
        background = c;

	// This is a bound property, so report the change to
	// any registered listeners.  (Cheap if there are none.)
	firePropertyChange("background", oldColor, c);
    }

    /**
     * Returns whether the background color has been explicitly set for this
     * Component. If this method returns <code>false</code>, this Component is
     * inheriting its background color from an ancestor.
     *
     * @return <code>true</code> if the background color has been explicitly
     *         set for this Component; <code>false</code> otherwise.
     * @since 1.4
     */
    public boolean isBackgroundSet() {
        return (background != null);
    }

    /**
     * Gets the font of this component.
     * @return This component's font. If a font has not been set
     * for this component, the font of its parent is returned.
     * @see #setFont
     * @since JDK1.0
     */
    public Font getFont() {
        Font font = this.font;
        if (font != null) {
            return font;
        }
        Container parent = this.parent;
        return (parent != null) ? parent.getFont() : null;
    }

    /**
     * Sets the font of this component.
     * @param f The font to become this component's font.
     * If this parameter is null then this component will inherit
     * the font of its parent.
     * @see #getFont
     * @since JDK1.0
     */
    public void setFont(Font f) {
        Font oldFont = font;
        font = f;

        // This is a bound property, so report the change to
        // any registered listeners.  (Cheap if there are none.)
        firePropertyChange("font", oldFont, font);
    }

    /**
     * Returns whether the font has been explicitly set for this Component. If
     * this method returns <code>false</code>, this Component is inheriting its
     * font from an ancestor.
     *
     * @return <code>true</code> if the font has been explicitly set for this
     *         Component; <code>false</code> otherwise.
     * @since 1.4
     */
    public boolean isFontSet() {
        return (font != null);
    }

    /**
     * Gets the locale of this component.
     * @return This component's locale. If this component does not
     * have a locale, the locale of its parent is returned.
     * @see #setLocale
     * @exception IllegalComponentStateException If the Component
     * does not have its own locale and has not yet been added to
     * a containment hierarchy such that the locale can be determined
     * from the containing parent.
     * @since  JDK1.1
     */
    public Locale getLocale() {
        Locale locale = this.locale;
        if (locale != null) {
            return locale;
        }
        Container parent = this.parent;
        if (parent == null) {
            throw new IllegalComponentStateException("This component must have a parent in order to determine its locale");
        } else {
            return parent.getLocale();
        }
    }

    /**
     * Sets the locale of this component.
     * @param l The locale to become this component's locale.
     * @see #getLocale
     * @since JDK1.1
     */
    public void setLocale(Locale l) {
        locale = l;
        // This could change the preferred size of the Component.
        if (valid) {
            invalidate();
        }
    }

    /**
     * Gets the instance of <code>ColorModel</code> used to display
     * the component on the output device.
     * @return The color model used by this component.
     * @see java.awt.image.ColorModel
     * @see java.awt.peer.ComponentPeer#getColorModel()
     * @see java.awt.Toolkit#getColorModel()
     * @since JDK1.0
     */
    public ColorModel getColorModel() {
        return getToolkit().getColorModel();
    }

    /**
     * Gets the location of this component in the form of a
     * point specifying the component's top-left corner.
     * The location will be relative to the parent's coordinate space.
     * <p>
     * Due to the asynchronous nature of native event handling, this
     * method can return outdated values (for instance, after several calls
     * of <code>setLocation()</code> in rapid succession).  For this
     * reason, the recommended method of obtaining a Component's position is
     * within <code>java.awt.event.ComponentListener.componentMoved()</code>,
     * which is called after the operating system has finished moving the
     * Component.
     * </p>
     * @return An instance of <code>Point</code> representing
     * the top-left corner of the component's bounds in the coordinate
     * space of the component's parent.
     * @see #setLocation
     * @see #getLocationOnScreen
     * @since JDK1.1
     */
    public Point getLocation() {
        return new Point(x, y);
    }

    /**
     * Gets the location of this component in the form of a point
     * specifying the component's top-left corner in the screen's
     * coordinate space.
     * @return An instance of <code>Point</code> representing
     * the top-left corner of the component's bounds in the
     * coordinate space of the screen.
     * @see #setLocation
     * @see #getLocation
     */
    public Point getLocationOnScreen() {
        synchronized (getTreeLock()) {
            Component c = this;
            Point location = new Point(0, 0);
            while (c != null && c.visible) {
                location.x += c.x;
                location.y += c.y;
                if (c instanceof Window)
                    return location;
                c = c.parent;
            }
            throw new IllegalComponentStateException("component must be showing on the screen to determine its location");
        }
    }

    /**
     * Moves this component to a new location. The top-left corner of
     * the new location is specified by the <code>x</code> and <code>y</code>
     * parameters in the coordinate space of this component's parent.
     * @param x The <i>x</i>-coordinate of the new location's
     * top-left corner in the parent's coordinate space.
     * @param y The <i>y</i>-coordinate of the new location's
     * top-left corner in the parent's coordinate space.
     * @see #getLocation
     * @see #setBounds
     * @since JDK1.1
     */
    public void setLocation(int x, int y) {
        setBounds(x, y, width, height);
    }

    /**
     * Moves this component to a new location. The top-left corner of
     * the new location is specified by point <code>p</code>. Point
     * <code>p</code> is given in the parent's coordinate space.
     * @param p The point defining the top-left corner
     * of the new location, given in the coordinate space of this
     * component's parent.
     * @see #getLocation
     * @see #setBounds
     * @since JDK1.1
     */
    public void setLocation(Point p) {
        setLocation(p.x, p.y);
    }

    /**
     * Returns the size of this component in the form of a
     * <code>Dimension</code> object. The <code>height</code>
     * field of the <code>Dimension</code> object contains
     * this component's height, and the <code>width</code>
     * field of the <code>Dimension</code> object contains
     * this component's width.
     * @return A <code>Dimension</code> object that indicates the
     * size of this component.
     * @see #setSize
     * @since JDK1.1
     */
    public Dimension getSize() {
        return new Dimension(width, height);
    }

    /**
     * Resizes this component so that it has width <code>width</code>
     * and <code>height</code>.
     * @param width The new width of this component in pixels.
     * @param height The new height of this component in pixels.
     * @see #getSize
     * @see #setBounds
     * @since JDK1.1
     */
    public void setSize(int width, int height) {
        setBounds(x, y, width, height);
    }

    /**
     * Resizes this component so that it has width <code>d.width</code>
     * and height <code>d.height</code>.
     * @param d The dimension specifying the new size
     * of this component.
     * @see #setSize
     * @see #setBounds
     * @since JDK1.1
     */
    public void setSize(Dimension d) {
        setSize(d.width, d.height);
    }

    /**
     * Gets the bounds of this component in the form of a
     * <code>Rectangle</code> object. The bounds specify this
     * component's width, height, and location relative to
     * its parent.
     * @return A rectangle indicating this component's bounds.
     * @see #setBounds
     * @see #getLocation
     * @see #getSize
     */
    public Rectangle getBounds() {
        return new Rectangle (x, y, width, height);
    }

    /**
     * Moves and resizes this component. The new location of the top-left
     * corner is specified by <code>x</code> and <code>y</code>, and the
     * new size is specified by <code>width</code> and <code>height</code>.
     * @param x The new <i>x</i>-coordinate of this component.
     * @param y The new <i>y</i>-coordinate of this component.
     * @param width The new <code>width</code> of this component.
     * @param height The new <code>height</code> of this
     * component.
     * @see java.awt.Component#getBounds
     * @see java.awt.Component#setLocation(int, int)
     * @see java.awt.Component#setLocation(java.awt.Point)
     * @see java.awt.Component#setSize(int, int)
     * @see java.awt.Component#setSize(java.awt.Dimension)
     * @JDK1.1
     */
    public void setBounds(int x, int y, int width, int height) {
        synchronized (getTreeLock()) {
            boolean resized = (this.width != width) || (this.height != height);
            boolean moved = (this.x != x) || (this.y != y);
            if (resized || moved) {
                // Bug Fix - 4662934
                // Remember the area this component occupied in its parent.
                int oldParentX = this.x;
                int oldParentY = this.y;
                int oldWidth = this.width;
                int oldHeight = this.height;                
                this.x = x;
                this.y = y;
                this.width = width;
                this.height = height;
                if (displayable) {
                    if (resized) {
                        invalidate();
                    }
                    if (parent != null && parent.valid) {
                        parent.invalidate();
                    }
                }
                if (resized) {
                    if (componentListener != null ||
                        (eventMask & AWTEvent.COMPONENT_EVENT_MASK) != 0) {
                        ComponentEvent e = new ComponentEvent(this,
                                ComponentEvent.COMPONENT_RESIZED);
                        Toolkit.getEventQueue().postEvent(e);
                        //SunToolkit.postEvent(appContext, e);
                        // Container.dispatchEventImpl will create
                        // HierarchyEvents
                    }
                }
                if (moved) {
                    if (componentListener != null ||
                        (eventMask & AWTEvent.COMPONENT_EVENT_MASK) != 0) {
                        ComponentEvent e = new ComponentEvent(this,
                                ComponentEvent.COMPONENT_MOVED);
                        Toolkit.getEventQueue().postEvent(e);
                        //SunToolkit.postEvent(appContext, e);
                    }
                }
                if (visible) {
                    // Bug Fix - 4662934                    
                    // Repaint the old area ...
                    if (parent != null) {
                        parent.repaint(oldParentX, oldParentY, oldWidth, oldHeight);                        
                    }
                    // ... then the new (these areas will be collapsed by
                    // coalesceEvents if they intersect).                    
                    repaint();                                        
                }
            }
        }
    }

    /**
     * Return the current x coordinate of the components origin.
     * This method is preferable to writing component.getBounds().x,
     * or component.getLocation().x because it doesn't cause any
     * heap allocations.
     *
     * @return the current x coordinate of the components origin.
     * @since 1.2
     */
    public int getX() {
        return x;
    }