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

Introduction

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

Prototype

public final native void setGlobalCompositeOperation(String globalCompositeOperation) ;

Source Link

Document

Sets the global composite operation.

Usage

From source file:com.lambourg.webgallery.client.widgets.TitleBarIcon.java

License:GNU General Public License

private void draw() {
    Context2d ctx;
    Canvas buffer = Canvas.createIfSupported();
    Image img;/*  w w  w  .  j a v  a2 s  .  co  m*/
    int size = Style.toPixelRatio(Style.titleIconSize);

    this.canvas.setCoordinateSpaceWidth(size);
    this.canvas.setCoordinateSpaceHeight(size + Style.toPixelRatio(1));
    buffer.setCoordinateSpaceWidth(size);
    buffer.setCoordinateSpaceHeight(size);

    if (this.active) {
        img = this.imgActive;
    } else {
        img = this.imgNormal;
    }

    //  We need to draw the icon itself in a separate buffer, and only
    //  after apply the shadow.
    //  The reason is that in order to draw the icon using the color we
    //  want, we need to use composite operations, and this is not
    //  compatible with the shadow effect we want.
    ctx = buffer.getContext2d();
    if (this.over) {
        ctx.setFillStyle("#fff");
    } else {
        ctx.setFillStyle("#ddd");
    }
    ctx.fillRect(0, 0, size, size);
    ctx.setGlobalCompositeOperation(Composite.DESTINATION_ATOP);
    ctx.drawImage(ImageElement.as(img.getElement()), 0, 0, size, size);
    ctx.restore();

    ctx = this.canvas.getContext2d();
    ctx.setShadowBlur(0.0);
    ctx.setShadowColor("#333");
    ctx.setShadowOffsetY(Style.toPixelRatio(1));

    ctx.drawImage(buffer.getCanvasElement(), 0, 0, size, size);
}

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