2004-07-29  Sven Neumann  <sven@gimp.org>

	* libgimpwidgets/gimppreviewarea.c: only invalidate the buffer
	on size_allocate; allocate a new one on the next call to
	gimp_preview_area_draw(). Fixed buffer offset in expose method.

	* libgimpwidgets/Makefile.am
	* libgimpwidgets/test-preview-area.c: more a benchmark than a
	test; quite similar to testrgb from the GTK+ source tree.