[news.eclipse.platform.swt] Background Color (return to default behavior

[jared.warren@xxxxxxxxx (Jared Warren)]

Hello all -

I have an org.eclipse.swt.widgets.Canvas.  I need to be able to change the 
background color on the Canvas, and then later return it to it's "default" 
state.  I'm doing this:

Canvas canvas = new Canvas(parent, SWT.NONE);
..
Color previousColor = canvas.getBackground();
canvas.setBackground(SWT.COLOR_DARK_GRAY);
..
canvas.setBackground(previousColor);

However, when this completes, the background is visibly not the same as it 
was prior.

Inspection reveals that the "background" field on canvas initializes to 
the value "-1" (which presumably means "do the default.")  However, after 
the code above runs, the value IS NOT "-1".  And, of course, because 
setBackground takes a Color as an argument, I don't think I can set it 
back to "-1".  This is especially troublesome in cases where the Canvas is 
in an ExpandItem (for example), because the background is not a "flat" 
color - instead, it is an OS provided background, so I can't even emulate 
the behavior by using a "similar" color.

If it would help, I can provide a complete test case.

Thanks for any guidance,
jared