2004-02-19  Michael Natterer  <mitch@gimp.org>

	* app/core/gimp.[ch]: added new signal "buffer_changed" and new
	function gimp_set_global_buffer() which emits it when the global
	buffer changes.

	* app/core/gimp-edit.c (gimp_edit_extract): use it instead
	of fiddling with gimp->global_buffer manually.

	* app/gui/image-menu.c: connect to "buffer_changed" and set the
	"Paste" menu entries sensitive. Fixes bug #134752.

	(image_menu_update): changed accordingly. Also changed a lot of
	buggy SET_SENSITIVE() lines which made menu items which work fine
	on any drawable insensitive when there were no layers (instead
	of no drawable).

	* app/gui/edit-commands.c: added new macro return_if_new_drawable()
	and use it instead of return_if_no_image() so we don't run
	into assertions if there is no active drawable.

	(cut,copy_named_buffer_callback): unfortunately had to introduce
	two new translated messages about not being able to cut/copy when
	there is no active drawable.