org.eclipse.swt.examples.graphics.BallTab.java Source code

Introduction

Here is the source code for org.eclipse.swt.examples.graphics.BallTab.java

Source

/*******************************************************************************
 * Copyright (c) 2006, 2015 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.swt.examples.graphics;

import java.util.LinkedList;

import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.Device;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Path;
import org.eclipse.swt.graphics.Transform;

/**
 * This tab uses alpha blending to simulate "ghosting" of a ball in movement.
 */
public class BallTab extends AnimatedGraphicsTab {

    BallCollection[] bc;

    /**
     * This inner class serves as a container for the data needed to display a
     * collection of balls.
     */
    static class BallCollection {
        float x, y; // position of ball
        float incX, incY; // values by which to move the ball
        int ball_size; // size (diameter) of the ball
        int capacity; // number of balls in the collection
        LinkedList<Float> prevx, prevy; // collection of previous x and y positions
        // of ball
        Color[] colors; // colors used for this ball collection

        public BallCollection(float x, float y, float incX, float incY, int ball_size, int capacity,
                Color[] colors) {
            this.x = x;
            this.y = y;
            this.incX = incX;
            this.incY = incY;
            this.ball_size = ball_size;
            this.capacity = capacity;
            prevx = new LinkedList<>();
            prevy = new LinkedList<>();
            this.colors = colors;
        }
    }

    @Override
    public void dispose() {
        bc[0] = bc[1] = bc[2] = bc[3] = bc[4] = null;
    }

    public BallTab(GraphicsExample example) {
        super(example);
        bc = new BallCollection[5];
    }

    @Override
    public String getCategory() {
        return GraphicsExample.getResourceString("Alpha"); //$NON-NLS-1$
    }

    @Override
    public String getText() {
        return GraphicsExample.getResourceString("Ball"); //$NON-NLS-1$
    }

    @Override
    public String getDescription() {
        return GraphicsExample.getResourceString("BallDescription"); //$NON-NLS-1$
    }

    @Override
    public int getInitialAnimationTime() {
        return 10;
    }

    @Override
    public void next(int width, int height) {
        for (int i = 0; i < bc.length; i++) {
            if (bc[i] == null)
                return;
            if (bc[i].prevx.size() == 0) {
                bc[i].prevx.addLast(Float.valueOf(bc[i].x));
                bc[i].prevy.addLast(Float.valueOf(bc[i].y));
            } else if (bc[i].prevx.size() == bc[i].capacity) {
                bc[i].prevx.removeFirst();
                bc[i].prevy.removeFirst();
            }

            bc[i].x += bc[i].incX;
            bc[i].y += bc[i].incY;

            float random = (float) Math.random();

            // right
            if (bc[i].x + bc[i].ball_size > width) {
                bc[i].x = width - bc[i].ball_size;
                bc[i].incX = random * -width / 16 - 1;
            }
            // left
            if (bc[i].x < 0) {
                bc[i].x = 0;
                bc[i].incX = random * width / 16 + 1;
            }
            // bottom
            if (bc[i].y + bc[i].ball_size > height) {
                bc[i].y = (height - bc[i].ball_size) - 2;
                bc[i].incY = random * -height / 16 - 1;
            }
            // top
            if (bc[i].y < 0) {
                bc[i].y = 0;
                bc[i].incY = random * height / 16 + 1;
            }
            bc[i].prevx.addLast(Float.valueOf(bc[i].x));
            bc[i].prevy.addLast(Float.valueOf(bc[i].y));
        }
    }

    @Override
    public void paint(GC gc, int width, int height) {
        if (!example.checkAdvancedGraphics())
            return;
        Device device = gc.getDevice();

        if (bc[0] == null) {
            bc[0] = new BallCollection(0, 0, 5, 5, 20, 20, new Color[] { device.getSystemColor(SWT.COLOR_GREEN) });
            bc[1] = new BallCollection(50, 300, 10, -5, 50, 10,
                    new Color[] { device.getSystemColor(SWT.COLOR_BLUE) });
            bc[2] = new BallCollection(250, 100, -5, 8, 25, 12,
                    new Color[] { device.getSystemColor(SWT.COLOR_RED) });
            bc[3] = new BallCollection(150, 400, 5, 8, 35, 14,
                    new Color[] { device.getSystemColor(SWT.COLOR_BLACK) });
            bc[4] = new BallCollection(100, 250, -5, -18, 100, 5,
                    new Color[] { device.getSystemColor(SWT.COLOR_MAGENTA) });
        }

        for (BallCollection ballCollection : bc) {
            for (int i = 0; i < ballCollection.prevx.size(); i++) {
                Transform transform = new Transform(device);
                transform.translate(ballCollection.prevx.get(ballCollection.prevx.size() - (i + 1)).floatValue(),
                        ballCollection.prevy.get(ballCollection.prevy.size() - (i + 1)).floatValue());
                gc.setTransform(transform);
                transform.dispose();

                Path path = new Path(device);
                path.addArc(0, 0, ballCollection.ball_size, ballCollection.ball_size, 0, 360);
                gc.setAlpha(255 - i * (255 / ballCollection.capacity));
                gc.setBackground(ballCollection.colors[0]);
                gc.fillPath(path);
                gc.drawPath(path);
                path.dispose();
            }
        }
    }
}