src/java.desktop/share/classes/javax/swing/Popup.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
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 * This code 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
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 * accompanied this code).
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package javax.swing;

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.GraphicsEnvironment;
import java.awt.Window;

import sun.awt.ModalExclude;

/**
 * Popups are used to display a <code>Component</code> to the user, typically
 * on top of all the other <code>Component</code>s in a particular containment
 * hierarchy. <code>Popup</code>s have a very small life cycle. Once you
 * have obtained a <code>Popup</code>, and hidden it (invoked the
 * <code>hide</code> method), you should no longer
 * invoke any methods on it. This allows the <code>PopupFactory</code> to cache
 * <code>Popup</code>s for later use.
 * <p>
 * The general contract is that if you need to change the size of the
 * <code>Component</code>, or location of the <code>Popup</code>, you should
 * obtain a new <code>Popup</code>.
 * <p>
 * <code>Popup</code> does not descend from <code>Component</code>, rather
 * implementations of <code>Popup</code> are responsible for creating
 * and maintaining their own <code>Component</code>s to render the
 * requested <code>Component</code> to the user.
 * <p>
 * You typically do not explicitly create an instance of <code>Popup</code>,
 * instead obtain one from a <code>PopupFactory</code>.
 *
 * @see PopupFactory
 *
 * @since 1.4
 */
public class Popup {
    /**
     * The Component representing the Popup.
     */
    private Component component;

    /**
     * Creates a <code>Popup</code> for the Component <code>owner</code>
     * containing the Component <code>contents</code>. <code>owner</code>
     * is used to determine which <code>Window</code> the new
     * <code>Popup</code> will parent the <code>Component</code> the
     * <code>Popup</code> creates to.
     * A null <code>owner</code> implies there is no valid parent.
     * <code>x</code> and
     * <code>y</code> specify the preferred initial location to place
     * the <code>Popup</code> at. Based on screen size, or other parameters,
     * the <code>Popup</code> may not display at <code>x</code> and
     * <code>y</code>.
     *
     * @param owner    Component mouse coordinates are relative to, may be null
     * @param contents Contents of the Popup
     * @param x        Initial x screen coordinate
     * @param y        Initial y screen coordinate
     * @throws IllegalArgumentException if contents is null
     */
    protected Popup(Component owner, Component contents, int x, int y) {
        this();
        if (contents == null) {
            throw new IllegalArgumentException("Contents must be non-null");
        }
        reset(owner, contents, x, y);
    }

    /**
     * Creates a <code>Popup</code>. This is provided for subclasses.
     */
    protected Popup() {
    }

    /**
     * Makes the <code>Popup</code> visible. If the <code>Popup</code> is
     * currently visible, this has no effect.
     */

    @SuppressWarnings("deprecation")
    public void show() {
        Component component = getComponent();

        if (component != null) {
            component.show();
        }
    }

    /**
     * Hides and disposes of the <code>Popup</code>. Once a <code>Popup</code>
     * has been disposed you should no longer invoke methods on it. A
     * <code>dispose</code>d <code>Popup</code> may be reclaimed and later used
     * based on the <code>PopupFactory</code>. As such, if you invoke methods
     * on a <code>disposed</code> <code>Popup</code>, indeterminate
     * behavior will result.
     */

    @SuppressWarnings("deprecation")
    public void hide() {
        Component component = getComponent();

        if (component instanceof JWindow) {
            component.hide();
            ((JWindow)component).getContentPane().removeAll();
        }
        dispose();
    }

    /**
     * Frees any resources the <code>Popup</code> may be holding onto.
     */
    void dispose() {
        Component component = getComponent();
        Window window = SwingUtilities.getWindowAncestor(component);

        if (component instanceof JWindow) {
            ((Window)component).dispose();
            component = null;
        }
        // If our parent is a DefaultFrame, we need to dispose it, too.
        if (window instanceof DefaultFrame) {
            window.dispose();
        }
    }

    /**
     * Resets the <code>Popup</code> to an initial state.
     */
    void reset(Component owner, Component contents, int ownerX, int ownerY) {
        if (getComponent() == null) {
            component = createComponent(owner);
        }

        Component c = getComponent();

        if (c instanceof JWindow) {
            JWindow component = (JWindow)getComponent();
            // Sets the proper location, and resets internal state of the window
            component.setBounds(ownerX, ownerY, 1, 1);
            component.getContentPane().add(contents, BorderLayout.CENTER);
            component.invalidate();
            component.validate();
            if(component.isVisible()) {
                // Do not call pack() if window is not visible to
                // avoid early native peer creation
                pack();
            }
        }
    }


    /**
     * Causes the <code>Popup</code> to be sized to fit the preferred size
     * of the <code>Component</code> it contains.
     */
    void pack() {
        Component component = getComponent();

        if (component instanceof Window) {
            ((Window)component).pack();
        }
    }

    /**
     * Returns the <code>Window</code> to use as the parent of the
     * <code>Window</code> created for the <code>Popup</code>. This creates
     * a new <code>DefaultFrame</code>, if necessary.
     */
    private Window getParentWindow(Component owner) {
        Window window = null;

        if (owner instanceof Window) {
            window = (Window)owner;
        }
        else if (owner != null) {
            window = SwingUtilities.getWindowAncestor(owner);
        }
        if (window == null) {
            window = new DefaultFrame();
        }
        return window;
    }

    /**
     * Creates the Component to use as the parent of the <code>Popup</code>.
     * The default implementation creates a <code>Window</code>, subclasses
     * should override.
     */
    Component createComponent(Component owner) {
        if (GraphicsEnvironment.isHeadless()) {
            // Generally not useful, bail.
            return null;
        }
        return new HeavyWeightWindow(getParentWindow(owner));
    }

    /**
     * Returns the <code>Component</code> returned from
     * <code>createComponent</code> that will hold the <code>Popup</code>.
     */
    Component getComponent() {
        return component;
    }


    /**
     * Component used to house window.
     */
    @SuppressWarnings("serial") // Superclass is not serializable across versions
    static class HeavyWeightWindow extends JWindow implements ModalExclude {
        HeavyWeightWindow(Window parent) {
            super(parent);
            setFocusableWindowState(false);
            setType(Window.Type.POPUP);

            // Popups are typically transient and most likely won't benefit
            // from true double buffering.  Turn it off here.
            getRootPane().setUseTrueDoubleBuffering(false);
            setAlwaysOnTop(true);
        }

        public void update(Graphics g) {
            paint(g);
        }

        @SuppressWarnings("deprecation")
        public void show() {
            this.pack();
            if (getWidth() > 0 && getHeight() > 0) {
                super.show();
            }
        }
    }


    /**
     * Used if no valid Window ancestor of the supplied owner is found.
     * <p>
     * PopupFactory uses this as a way to know when the Popup shouldn't
     * be cached based on the Window.
     */
    @SuppressWarnings("serial") // JDK-implementation class
    static class DefaultFrame extends Frame {
    }
}