Bug 149878

Description Mark Siegel 2006-07-06 14:52:18 EDT

It seems that when an EditPart is rendered using a figure that has transparency, strange drawing artifacts sometimes appear on the rendered figure.

This usually happens when either:
a) Another EditPart is being dragged over top of the figure with transparency
b) The EditPart with transparency is off screen and the editor is scrolled to bring it on screen.

To reproduce, I've altered the Sample GEF Shapes Editor example (see code snippet below).  Insert a rectangle part and place it mostly off the screen to the top.  Scroll up to bring it completely into view.  Notice the strange drawing artifacts on the image.

My system configuration is RHEL AS4 (Update 1).

Replacing ShapeEditPart.createFigureForModel()

private IFigure createFigureForModel() {
	if (getModel() instanceof EllipticalShape) {
		return new Ellipse();
	} else if (getModel() instanceof RectangularShape) {
		return new Figure()
        {
            public void paintFigure (Graphics graphics)
            {
                Image image = ImageCreator.createImage (100,100);

                try
                {
                    graphics.setInterpolation (SWT.LOW);
                    graphics.drawImage (image, new Rectangle (image.getBounds ()), getBounds ().getCopy ());
                }
                catch (SWTException e)
                {
                }
            }
        };
	} else {
		// if Shapes gets extended the conditions above must be updated
		throw new IllegalArgumentException();
	}
}

static class ImageCreator
{
    private static final int BLACK = 0x000000;
    private static final int TRANSPARENT_COLOR = 0xFFFFFE;
    private static final PaletteData PALETTE_DATA = new PaletteData (0xFF0000, 0xFF00, 0xFF);
    
    public static Image createImage (int width, int height)
    {
            ImageData  swtImageData = new ImageData (height, width, 24, PALETTE_DATA);
            swtImageData.transparentPixel = TRANSPARENT_COLOR;
            
            byte[] data = swtImageData.data;
            for (int i = 0; i < width; i++)
            {
                int idx = i * swtImageData.bytesPerLine;
                for (int j = 0; j < height; j++)
                {
                    // draw a grid
                    int rgb = i % 8 == 7 || j % 8 == 7 ? BLACK : TRANSPARENT_COLOR;
                    for (int k = swtImageData.depth - 8; k >= 0; k -= 8)
                    {
                        data[idx++] = (byte) ((rgb >> k) & 0xFF);
                    }
                }
            }

            return new Image (Display.getDefault (), swtImageData);
    }
}