2004-05-26  Michael Natterer  <mitch@gimp.org>

	* app/paint/gimppaintcore.[ch] (gimp_paint_core_paste)
	(gimp_paint_core_replace): replaced the "MaskBuf *paint_mask"
	parameters by "PixelRegion *mask_bufPR", so subclasses can pass in
	any kind of paint_mask buffer and are not restricted to MaskBufs.

	Also removes implicit knowledge about the MaskBuf originating from
	a brush in paint_mask_to_canvas_buf() and _to_canvas_tiles() which
	don't need to offset the mask by width/2 height/2 any more.

	Made gimp_paint_core_validate_undo_tiles() and
	gimp_paint_core_validate_canvas_tiles() protected functions.

	* app/paint/gimpbrushcore.c (gimp_brush_core_paste_canvas)
	(gimp_brush_core_replace_canvas): create correctly positioned
	PixelRegions from the MaskBufs before passing them to the
	paint_core.