com.turbomanage.demo.client.Sunflower.java Source code

Introduction

Here is the source code for com.turbomanage.demo.client.Sunflower.java

Source

package com.turbomanage.demo.client;

import com.google.gwt.canvas.client.Canvas;
import com.google.gwt.canvas.dom.client.Context2d;
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.event.logical.shared.ValueChangeEvent;
import com.google.gwt.event.logical.shared.ValueChangeHandler;
import com.google.gwt.gen2.client.IntegerSlider;
import com.google.gwt.user.client.ui.AbsolutePanel;
import com.google.gwt.user.client.ui.Anchor;
import com.google.gwt.user.client.ui.Composite;
import com.google.gwt.user.client.ui.Grid;
import com.google.gwt.user.client.ui.Image;
import com.google.gwt.user.client.ui.RootPanel;
import com.google.gwt.user.client.ui.VerticalPanel;

/**
 * Copyright 2011 David M. Chandler
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * @author David M. Chandler (dchandler@turbomanage.com)
 */
public class Sunflower extends Composite implements EntryPoint {

    private static final int SEED_RADIUS = 2;
    private static final int SCALE_FACTOR = 4;
    public static final double PI2 = Math.PI * 2;
    public static final double PHI = (Math.sqrt(5) + 1) / 2;
    private Canvas canvas;
    private Context2d front;
    private int numSeeds;
    private int maxSeeds = 1000;
    // max diameter in coordinate space
    private int maxD = (int) (Math.sqrt(maxSeeds) * SCALE_FACTOR * 2 + SEED_RADIUS * 2);
    private VerticalPanel vPanel = new VerticalPanel();
    private IntegerSlider numSeedsSlider = new IntegerSlider(0, maxSeeds);
    private int yc = maxD / 2;
    private int xc = maxD / 2;
    private AbsolutePanel absolutePanel;

    public void onModuleLoad() {
        RootPanel.get("gwt").add(new Sunflower());
    }

    public Sunflower() {
        canvas = Canvas.createIfSupported();
        canvas.setPixelSize(2 * maxD, 2 * maxD);
        // coordinate space = 1/2 pixel space for better performance
        canvas.setCoordinateSpaceHeight(maxD);
        canvas.setCoordinateSpaceWidth(maxD);
        front = canvas.getContext2d();

        initSlider();
        initPanel();

        initWidget(vPanel);
    }

    private void initSlider() {
        numSeedsSlider.setNumTicks(0);
        numSeedsSlider.setStepSize(1);
        numSeedsSlider.setNumLabels(10);
        numSeedsSlider.setWidth("100%");
        numSeedsSlider.addValueChangeHandler(new ValueChangeHandler<Double>() {
            @Override
            public void onValueChange(ValueChangeEvent<Double> event) {
                numSeeds = (int) Math.round(event.getValue());
                drawFrame();
            }
        });
    }

    private void initPanel() {
        Grid grid = new Grid(1, 3);
        grid.getElement().setId("grid");
        grid.setWidth("100%");
        grid.setWidget(0, 0, new Image("r.png"));
        grid.setWidget(0, 1, new Image("theta.png"));
        grid.setWidget(0, 2, new Image("phi.png"));
        vPanel.add(numSeedsSlider);
        vPanel.add(grid);
        absolutePanel = new AbsolutePanel();
        absolutePanel.add(canvas);
        vPanel.add(absolutePanel);
        vPanel.add(new Anchor("Blog post", "http://turbomanage.wordpress.com/2011/06/29/friday-fun-with-gwt/"));
        vPanel.add(new Anchor("Source code", "http://code.google.com/p/gwt-sunflower/"));
    }

    /**
     * Draw the complete figure for the current
     * number of seeds
     */
    private void drawFrame() {
        front.clearRect(0, 0, maxD, maxD);
        for (int i = 0; i < numSeeds; i++) {
            double theta = i * PI2 / PHI;
            double r = Math.sqrt(i) * SCALE_FACTOR;
            double x = xc + r * Math.cos(theta);
            double y = yc - r * Math.sin(theta);
            drawSeed(x, y);
        }
    }

    /**
     * Draw a small circle representing a seed centered at (x,y)
     * 
     * @param x Center of the seed head
     * @param y Center of the seed head
     */
    private void drawSeed(double x, double y) {
        front.beginPath();
        front.setLineWidth(2);
        front.setFillStyle("orange");
        front.setStrokeStyle("orange");
        front.arc(x, y, SEED_RADIUS, 0, PI2);
        front.fill();
        front.closePath();
        front.stroke();
    }

}