[Gimp-developer] Background color property for GIMP images

[saulgoode at flashingtwelve.brickfilms.com]

Quoting David Gowers <00ai99 at gmail.com>:

> The eraser currently does change color values, in the case of layers
> without alpha (it's like using paintbrush or pencil with the
> background color). Yahvuu's proposition would make sure it never
> changed color values because there would be no layers without alpha.

I don't understand the last sentence (perhaps I don't understand  
Yahvuu's proposition correctly). If color values are never changed,  
the only place that erasures would result in an "image background  
color" (being revealed) is on the bottommost layer. Is that what is  
being proposed?

If so, then I would consider the lack of consistency in the tool's  
behavior across layers to be a problem.

If it is not so, what determines whether or not erasure results in the  
RGB part of the "image background color" being blended with the layer  
contents?