com.philbeaudoin.quebec.client.widget.FullCanvas.java Source code

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Here is the source code for com.philbeaudoin.quebec.client.widget.FullCanvas.java

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/**
 * Copyright 2012 Philippe Beaudoin
 *
 * 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 com.philbeaudoin.quebec.client.widget;

import com.google.gwt.canvas.client.Canvas;
import com.google.gwt.core.client.Scheduler;
import com.google.gwt.core.client.Scheduler.ScheduledCommand;
import com.google.gwt.event.dom.client.HasAllMouseHandlers;
import com.google.gwt.event.dom.client.MouseDownHandler;
import com.google.gwt.event.dom.client.MouseMoveHandler;
import com.google.gwt.event.dom.client.MouseOutHandler;
import com.google.gwt.event.dom.client.MouseOverHandler;
import com.google.gwt.event.dom.client.MouseUpHandler;
import com.google.gwt.event.dom.client.MouseWheelHandler;
import com.google.gwt.event.logical.shared.HasResizeHandlers;
import com.google.gwt.event.logical.shared.ResizeEvent;
import com.google.gwt.event.logical.shared.ResizeHandler;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.uibinder.client.UiConstructor;
import com.google.gwt.user.client.ui.Composite;
import com.google.gwt.user.client.ui.RequiresResize;

/**
 * A canvas that always resizes to take as much room as possible within its parent while respecting
 * a specified aspect ratio.
 *
 * @author Philippe Beaudoin <philippe.beaudoin@gmail.com>
 */
public class FullCanvas extends Composite implements RequiresResize, HasAllMouseHandlers, HasResizeHandlers {

    private final double targetAspectRatio;
    private final Canvas canvas;

    /**
     * A canvas that always resizes to take as much room as possible within its parent while
     * respecting a specified aspect ratio.
     * @param targetAspectRatio The desired aspect ratio of the canvas.
     */
    @UiConstructor
    public FullCanvas(double targetAspectRatio) {
        this.targetAspectRatio = targetAspectRatio;
        canvas = Canvas.createIfSupported();
        // TODO(beaudoin): Do something if canvas cannot be created.
        initWidget(canvas);
    }

    public Canvas asCanvas() {
        return canvas;
    }

    @Override
    protected void onLoad() {
        super.onLoad();
        Scheduler.get().scheduleDeferred(new ScheduledCommand() {
            @Override
            public void execute() {
                onResize();
            }
        });
    }

    @Override
    public void onResize() {
        int width = getParent().getOffsetWidth();
        int height = getParent().getOffsetHeight();
        int top = 0;
        int left = 0;
        double aspectRatio = (double) width / (double) height;
        if (targetAspectRatio > aspectRatio) {
            // Constrain canvas width.
            top = height;
            height = (int) (width / targetAspectRatio);
            top = (top - height) / 2;
        } else {
            // Constrain canvas height.
            left = width;
            width = (int) (height * targetAspectRatio);
            left = (left - width) / 2;
        }
        canvas.getElement().getStyle().setPropertyPx("top", top);
        canvas.getElement().getStyle().setPropertyPx("left", left);
        canvas.setPixelSize(width, height);
        canvas.setCoordinateSpaceWidth(width);
        canvas.setCoordinateSpaceHeight(height);

        ResizeEvent.fire(this, width, height);
    }

    @Override
    public HandlerRegistration addMouseDownHandler(MouseDownHandler handler) {
        return canvas.addMouseDownHandler(handler);
    }

    @Override
    public HandlerRegistration addMouseUpHandler(MouseUpHandler handler) {
        return canvas.addMouseUpHandler(handler);
    }

    @Override
    public HandlerRegistration addMouseOutHandler(MouseOutHandler handler) {
        return canvas.addMouseOutHandler(handler);
    }

    @Override
    public HandlerRegistration addMouseOverHandler(MouseOverHandler handler) {
        return canvas.addMouseOverHandler(handler);
    }

    @Override
    public HandlerRegistration addMouseMoveHandler(MouseMoveHandler handler) {
        return canvas.addMouseMoveHandler(handler);
    }

    @Override
    public HandlerRegistration addMouseWheelHandler(MouseWheelHandler handler) {
        return canvas.addMouseWheelHandler(handler);
    }

    @Override
    public HandlerRegistration addResizeHandler(ResizeHandler handler) {
        return addHandler(handler, ResizeEvent.getType());
    }
}