[racket] Setting the background color of a text-field% instance

At Tue, 3 Aug 2010 11:54:35 -0600, Doug Williams wrote:
> Is there an easy way to set the background color of a text-field% instance?
> I see that get-editor returns the text% object that implements it. But I
> haven't found any magic combination of style changes or getting the dc
> object and setting the text background etc. that works.

There was no way to set the background color in a `text-field%' object.
You can set the background color of text through a style, but that's
not the same thing as setting the background for the entire field.

I've added a `set-field-background' method to `text-field%'.