2003-06-02  Michael Natterer  <mitch@gimp.org>

	Implemented DISSOLVE_MODE the way it should have always been.
	Fixes bug #107402.

	* app/paint-funcs-generic.h (struct apply_layer_mode_struct): added
	"guchar *mask" so it can be used by the layer mode.

	(dissolve_pixels): take an additional "mask" parameter and
	dissolve the pixels according to the *combined* opacity of the
	pixel's alpha, the opacity and the mask. Removed a wrong comment
	about why we call g_rand_int() x times before we start to use its
	values.

	(layer_dissolve_mode): pass the mask to dissolve_pixels(). No need
	to call add_alpha_pixels() since we overwrite the dest buffer
	entirely in disolve_pixels().

	* app/paint-funcs.c (initial_sub_region, combine_sub_region):
	allocate the buffer large enough for DISSOLVE (which always needs
	an alpha channel). Pass the mask to the layer mode functions.
	Discard opacity and mask after applying DISSOLVE since it
	"consumes" all transparency.