How to smoothly scroll through a SWT composition?

Question

I use SWT ScrolledComposite, but when I scroll on Windows, I get some tearing / flickering if I scroll them fast. What can I do to double the buffer or reduce this effect, or what can I do to override the default scroll functionality and make it smoother? There are text fields in the scroll pane, so I don’t think the canvas will work.

Answer 1

The trick is to play with a delay and use one-pixel scrolling.

Here is a piece of code, as I actually do it:

public void scrollOnePixelUp() {
    scrolledComposite.getContent().setLocation(0, scrolledComposite.getContent().getLocation().y - 1);
}

public void scrollOnePixelDown() {
    scrolledComposite.getContent().setLocation(0, scrolledComposite.getContent().getLocation().y + 1);
}

private int pixelScrollDelay = 50;//ms

scrollingThread = new Thread() {
    public void run() {
        doScrolling = true;
        int i = 0;
        while((i < scrollLength) && running && doScrolling) {
            i++;

            if (d.isDisposed())
                return;
            d.asyncExec(new Runnable() {
                public void run() {
                    if (scrollUp)
                        scrollOnePixelUp();
                    else
                        scrollOnePixelDown();
                }                       
            });


            try {
                sleep(pixelScrollDelay);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        doScrolling = false;
    }
};

Hope this helps!