Example usage for com.google.gwt.canvas.dom.client Context2d clearRect

Introduction

In this page you can find the example usage for com.google.gwt.canvas.dom.client Context2d clearRect.

Prototype

public final native void clearRect(double x, double y, double w, double h) ;

Source Link

Document

Clears a rectangle.

Usage

From source file:org.rstudio.core.client.widget.FontDetector.java

License:Open Source License

public static boolean isFontSupported(String fontName) {
    SimplePanel panel = null;/*from  w  ww . ja  v a 2 s. co  m*/
    try {
        // default font name as a reference point
        final String defaultFontName = "Arial";
        if (defaultFontName.equals(fontName))
            return true;

        // make sure canvas is supported
        if (!Canvas.isSupported())
            return false;

        // add a temporary div to the dom
        panel = new SimplePanel();
        panel.setHeight("200px");
        panel.getElement().getStyle().setVisibility(Visibility.HIDDEN);
        panel.getElement().getStyle().setOverflow(Overflow.SCROLL);
        RootPanel.get().add(panel, -2000, -2000);

        // add a canvas element to the div and get the 2d drawing context
        final Canvas canvas = Canvas.createIfSupported();
        canvas.setWidth("512px");
        canvas.setHeight("64px");
        canvas.getElement().getStyle().setLeft(400, Unit.PX);
        canvas.getElement().getStyle().setBackgroundColor("#ffe");
        panel.add(canvas);
        final Context2d ctx = canvas.getContext2d();
        ctx.setFillStyle("#000000");

        // closure to generate a hash for a font
        class HashGenerator {
            public String getHash(String fontName) {
                ctx.setFont("57px " + fontName + ", " + defaultFontName);
                int width = canvas.getOffsetWidth();
                int height = canvas.getOffsetHeight();
                ctx.clearRect(0, 0, width, height);
                ctx.fillText("TheQuickBrownFox", 2, 50);
                return canvas.toDataUrl();
            }
        }
        ;

        // get hashes and compare them
        HashGenerator hashGenerator = new HashGenerator();
        String defaultHash = hashGenerator.getHash(defaultFontName);
        String fontHash = hashGenerator.getHash(fontName);
        return !defaultHash.equals(fontHash);
    } catch (Exception ex) {
        Debug.log(ex.toString());
        return false;
    } finally {
        if (panel != null)
            RootPanel.get().remove(panel);
    }
}

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From source file:org.rstudio.core.client.widget.ProgressSpinner.java

License:Open Source License

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();/*from   w ww  .j ava 2 s.c o  m*/
        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();
    }
}

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From source file:stroom.widget.htree.client.ShadowBox.java

License:Apache License

private void clear(final Context2d ctx, final Bounds bounds) {
    ctx.clearRect(bounds.getX() - 2, bounds.getY() - 2, bounds.getWidth() + 4, bounds.getHeight() + 4);
}

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From source file:web.diva.client.somclust.view.MaxTreeZoomImage.java

public void buffer(Context2d back, Context2d front) {
    front.beginPath();/*from   w w w  . java2  s .com*/
    front.clearRect(0, 0, width, height);
    front.drawImage(back.getCanvas(), 0, 0);
}

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