Symantec Visual Cafe for Java 2.5/symantec-visual-cafe-2.5-database-dev-edition.iso/Visual Cafe Pro v1.0/SOURCE.BIN/InvisibleButton.java

Java Source | 1997-06-19 | 5.4 KB | 153 lines

package symantec.itools.awt;

import java.awt.Canvas;
import java.awt.Component;
import java.awt.Container;
import java.awt.Event;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Rectangle;

//    01/02/97    RKM    Changed paintComponent to not cause recursive drawing on overlap
//    01/02/97    RKM    Changed paintComponent to flush image after it is used
//    01/16/97    RKM    Added override of update to avoid flicker
//    01/18/07    RKM    Added more documentation and checked return from img.getGraphics
//    01/29/97    TWB    Integrated changes from Windows and RKM's changes
//     01/29/97    TWB    Integrated changes from Macintosh
//     02/01/97    RKM    Extracted transparency drawing trick into TransparencyTrickUtils

/**
 * Use this component to create an invisible area, usually within an image,
 * that initiates an action when clicked. Specifically, use InvisibleButton to
 * <UL>
 * <DT>╖ create a "hot spot" on an image or on a component</DT>
 * <DT>╖ accept or yield focus</DT>
 * <DT>╖ respond to a user event</DT>
 * <DT>╖ send an action event to another component</DT>
 * </UL>
 * Button tips:
 * <UL>
 * <DT>╖ Buttons accept and yield focus automatically by default.</DT>
 * <DT>╖ Buttons accept clicked events automatically by default.</DT>
 * <DT>╖ To send an action event to another component, use the Interaction
 * Wizard. Optionally, you can override the InvisibleButtonÆs click event in
 * project source code.</DT>
 * <DT>╖ Overlapping components - browsers handle components layered on each
 * other differently. Some browsers display/layer the InvisibleButtons on top
 * of a particular component, while others display them underneath. Therefore,
 * it often requires two sets of InvisibleButtons to ensure that one is "on top",
 * one on top of the particular component and the other underneath.
 * </UL>
 * Implements the Runnable interface to support threads.
 * <p>
 *
 */
public class InvisibleButton
    extends Canvas
    implements TransparencyTrick
{
    /**
     * True if the button is currently pressed.
     */
    protected boolean pressed;

    /**
     * Constructs an InvisibleButton.
     */
    public InvisibleButton() {
        pressed = false;
    }

    /**
     * Handles redrawing of this component on the screen.
     * This is a standard Java AWT method which gets called by the Java
     * AWT (repaint()) to handle repainting this component on the screen.
     * The graphics context clipping region is set to the bounding rectangle
     * of this component and its <0,0> coordinate is this component's
     * top-left corner.
     * Typically this method paints the background color to clear the
     * component's drawing space, sets graphics context to be the foreground
     * color, and then calls paint() to draw the component.
     *
     * It is overridden here to prevent the flicker associated with the standard
     * update() method's repainting of the background before painting the component
     * itself.
     *
     * @param g the graphics context
     * @see java.awt.Component#repaint
     * @see #paint
     */
    public void update(Graphics g)
    {
        paint(g);
    }

    /**
     * Paints this component using the given graphics context.
     * This is a standard Java AWT method which typically gets called
     * by the AWT to handle painting this component. It paints this component
     * using the given graphics context. The graphics context clipping region
     * is set to the bounding rectangle of this component and its <0,0>
     * coordinate is this component's top-left corner.
     * It paints what is under the button, so as to appear invisible.
     * @param g the graphics context used for painting
     * @see java.awt.Component#repaint
     * @see #update
     */
    public void paint(Graphics g) {
        TransparencyTrickUtils.paintComponentsBehind(this, g);
    }

    /**
     * Processes MOUSE_DOWN events.
     * This is a standard Java AWT method which gets called by the AWT
     * method handleEvent() in response to receiving a MOUSE_DOWN
     * event. These events occur when the mouse button is pressed while
     * inside this component.
     *
     * @param e the event
     * @param x the component-relative horizontal coordinate of the mouse
     * @param y the component-relative vertical coordinate of the mouse
     *
     * @return always true since the event was handled
     *
     * @see #mouseUp
     * @see java.awt.Component#handleEvent
     */
    public boolean mouseDown(Event e, int x, int y)
    {
        pressed = true;

        return true;
    }

    /**
     * Processes MOUSE_UP events.
     * This is a standard Java AWT method which gets called by the AWT
     * method handleEvent() in response to receiving a MOUSE_UP
     * event. These events occur when the mouse button is released while
     * inside this component.
     * If the mouse was pressed inside the button then an event is posted.
     *
     * @param e the event
     * @param x the component-relative horizontal coordinate of the mouse
     * @param y the component-relative vertical coordinate of the mouse
     *
     * @return always true since the event was handled
     *
     * @see #mouseDown
     * @see java.awt.Component#handleEvent
     */
    public boolean mouseUp(Event e, int x, int y)
    {
        if (pressed)
        {
            pressed = false;
            postEvent(new Event(this, Event.ACTION_EVENT, null));
        }

        return true;
    }
}