org.rstudio.core.client.widget.ProgressSpinner.java Source code

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Here is the source code for org.rstudio.core.client.widget.ProgressSpinner.java

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/*
 * ProgressSpinner.java
 *
 * Copyright (C) 2009-16 by RStudio, Inc.
 *
 * Unless you have received this program directly from RStudio pursuant
 * to the terms of a commercial license agreement with RStudio, then
 * this program is licensed to you under the terms of version 3 of the
 * GNU Affero General Public License. This program is distributed WITHOUT
 * ANY EXPRESS OR IMPLIED WARRANTY, INCLUDING THOSE OF NON-INFRINGEMENT,
 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Please refer to the
 * AGPL (http://www.gnu.org/licenses/agpl-3.0.txt) for more details.
 *
 */
package org.rstudio.core.client.widget;

import com.google.gwt.user.client.ui.Composite;
import com.google.gwt.user.client.ui.HTMLPanel;

import org.rstudio.core.client.Debug;

import com.google.gwt.canvas.client.Canvas;
import com.google.gwt.canvas.dom.client.Context2d;
import com.google.gwt.canvas.dom.client.Context2d.LineCap;
import com.google.gwt.core.client.Scheduler;

public class ProgressSpinner extends Composite {
    public ProgressSpinner(int color) {
        // compute sizes
        outerRadius_ = (COORD_SIZE / 2) - 10;
        innerRadius_ = (outerRadius_ / 2) + 5;
        color_ = color == COLOR_WHITE ? "255, 255, 255" : "0, 0, 0";

        // create canvas host
        canvas_ = Canvas.createIfSupported();
        if (canvas_ == null) {
            Debug.log("Can't create progress spinner (no HTML5 canvas support)");
            initWidget(new HTMLPanel(""));
            return;
        }

        initWidget(canvas_);

        // initialize canvas
        canvas_.setCoordinateSpaceWidth(COORD_SIZE);
        canvas_.setCoordinateSpaceHeight(COORD_SIZE);

        // perform initial draw and start animation
        redraw();
        Scheduler.get().scheduleFixedPeriod(new Scheduler.RepeatingCommand() {
            @Override
            public boolean execute() {
                frame_++;
                redraw();
                return !complete_;
            }
        }, FRAME_RATE_MS);
    }

    public void detach() {
        complete_ = true;
    }

    private void redraw() {
        Context2d ctx = canvas_.getContext2d();
        double center = COORD_SIZE / 2;
        // clear canvas (we draw with an alpha channel so otherwise would stack)
        ctx.clearRect(0, 0, COORD_SIZE, COORD_SIZE);
        for (int i = 0; i < NUM_BLADES; i++) {
            // compute angle for this blade
            double theta = ((2 * Math.PI) / NUM_BLADES) * i;
            double sin = Math.sin(theta);
            double cos = Math.cos(theta);

            // set line drawing context
            ctx.beginPath();
            ctx.setLineWidth(BLADE_WIDTH);
            ctx.setLineCap(LineCap.ROUND);

            // compute transparency for this blade
            double alpha = 1.0 - (((double) ((i + frame_) % NUM_BLADES)) / ((double) NUM_BLADES));
            ctx.setStrokeStyle("rgba(" + color_ + ", " + alpha + ")");

            // draw the blade
            ctx.moveTo(center + sin * innerRadius_, center + cos * innerRadius_);
            ctx.lineTo(center + sin * outerRadius_, center + cos * outerRadius_);
            ctx.stroke();
        }
    }

    // drawing parameters 
    private final static int NUM_BLADES = 12;
    private final static int BLADE_WIDTH = 9;
    private final static int COORD_SIZE = 100;
    private final static int FRAME_RATE_MS = 75;

    public final static int COLOR_WHITE = 0;
    public final static int COLOR_BLACK = 1;

    private final int innerRadius_;
    private final int outerRadius_;
    private final Canvas canvas_;
    private final String color_;

    private int frame_ = 0;
    private boolean complete_ = false;
}