anagram.client.GwtCanvasDemo.java Source code

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Here is the source code for anagram.client.GwtCanvasDemo.java

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/*
 * Copyright 2011 Google Inc.
 *
 * 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.
 */

package anagram.client;

import com.google.gwt.canvas.client.Canvas;
import com.google.gwt.canvas.dom.client.Context2d;
import com.google.gwt.canvas.dom.client.CssColor;
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.dom.client.Touch;
import com.google.gwt.event.dom.client.GestureStartEvent;
import com.google.gwt.event.dom.client.GestureStartHandler;
import com.google.gwt.event.dom.client.MouseMoveEvent;
import com.google.gwt.event.dom.client.MouseMoveHandler;
import com.google.gwt.event.dom.client.MouseOutEvent;
import com.google.gwt.event.dom.client.MouseOutHandler;
import com.google.gwt.event.dom.client.TouchEndEvent;
import com.google.gwt.event.dom.client.TouchEndHandler;
import com.google.gwt.event.dom.client.TouchMoveEvent;
import com.google.gwt.event.dom.client.TouchMoveHandler;
import com.google.gwt.user.client.Timer;
import com.google.gwt.user.client.ui.Label;
import com.google.gwt.user.client.ui.RootPanel;

public class GwtCanvasDemo implements EntryPoint {
    static final String holderId = "canvasholder";

    static final String upgradeMessage = "Your browser does not support the HTML5 Canvas. Please upgrade your browser to view this demo.";

    Canvas canvas;
    Canvas backBuffer;
    LogoGroup logoGroup;
    BallGroup ballGroup;
    Lens lens;

    // mouse positions relative to canvas
    int mouseX, mouseY;

    //timer refresh rate, in milliseconds
    static final int refreshRate = 25;

    // canvas size, in px
    static final int height = 400;
    static final int width = 400;

    final CssColor redrawColor = CssColor.make("rgba(255,255,255,0.6)");
    Context2d context;
    Context2d backBufferContext;

    public void onModuleLoad() {
        canvas = Canvas.createIfSupported();
        backBuffer = Canvas.createIfSupported();
        if (canvas == null) {
            RootPanel.get(holderId).add(new Label(upgradeMessage));
            return;
        }

        // init the canvases
        canvas.setWidth(width + "px");
        canvas.setHeight(height + "px");
        canvas.setCoordinateSpaceWidth(width);
        canvas.setCoordinateSpaceHeight(height);
        backBuffer.setCoordinateSpaceWidth(width);
        backBuffer.setCoordinateSpaceHeight(height);
        RootPanel.get(holderId).add(canvas);
        context = canvas.getContext2d();
        backBufferContext = backBuffer.getContext2d();

        // init the objects
        logoGroup = new LogoGroup(width, height, 18, 165);
        ballGroup = new BallGroup(width, height);
        lens = new Lens(35, 15, width, height, new Vector(320, 150), new Vector(1, 1));

        // init handlers
        initHandlers();

        // setup timer
        final Timer timer = new Timer() {
            @Override
            public void run() {
                doUpdate();
            }
        };
        timer.scheduleRepeating(refreshRate);
    }

    void doUpdate() {
        // update the back canvas
        backBufferContext.setFillStyle(redrawColor);
        backBufferContext.fillRect(0, 0, width, height);
        logoGroup.update(mouseX, mouseY);
        ballGroup.update(mouseX, mouseY);
        logoGroup.draw(backBufferContext);
        ballGroup.draw(backBufferContext);

        // update the front canvas
        lens.update();
        lens.draw(backBufferContext, context);
    }

    void initHandlers() {
        canvas.addMouseMoveHandler(new MouseMoveHandler() {
            public void onMouseMove(MouseMoveEvent event) {
                mouseX = event.getRelativeX(canvas.getElement());
                mouseY = event.getRelativeY(canvas.getElement());
            }
        });

        canvas.addMouseOutHandler(new MouseOutHandler() {
            public void onMouseOut(MouseOutEvent event) {
                mouseX = -200;
                mouseY = -200;
            }
        });

        canvas.addTouchMoveHandler(new TouchMoveHandler() {
            public void onTouchMove(TouchMoveEvent event) {
                event.preventDefault();
                if (event.getTouches().length() > 0) {
                    Touch touch = event.getTouches().get(0);
                    mouseX = touch.getRelativeX(canvas.getElement());
                    mouseY = touch.getRelativeY(canvas.getElement());
                }
                event.preventDefault();
            }
        });

        canvas.addTouchEndHandler(new TouchEndHandler() {
            public void onTouchEnd(TouchEndEvent event) {
                event.preventDefault();
                mouseX = -200;
                mouseY = -200;
            }
        });

        canvas.addGestureStartHandler(new GestureStartHandler() {
            public void onGestureStart(GestureStartEvent event) {
                event.preventDefault();
            }
        });
    }
}