2005-08-28  Michael Natterer  <mitch@gimp.org>

	Immplement "Sample Merged" for the clone tool. Fixes bug #123627.

	* app/paint/gimppaintcore.[ch] (struct GimpPaintCore): added
	members "saved_proj_tiles" which stores the unmodified projection,
	"orig_proj_buf" which stores the unmodified temp paint application
	buf and "use_saved_proj" which controls if all the additional
	stuff should be allocated and managed.

	(gimp_paint_core_start): allocate the saved_proj_tiles if needed.

	(gimp_paint_core_get_orig_proj): new function like
	gimp_paint_core_get_orig_image() which returns unmodified
	projection pixels for paint application.

	(gimp_paint_core_validate_saved_proj_tiles): new function like
	gimp_paint_core_validate_undo_tiles() which copies the tiles that
	will be dirtied to saved_proj_tiles.

	(gimp_paint_core_paste): call above save_proj_tiles() so
	projection tiles are saved before dirtying them.

	* app/paint/gimpclone.[ch]: replaced member src_drawable by
	src_pickable and use the image's projection if sample_merged it
	TRUE. Adjust src offsets accordingly and use GimpPaintCore's new
	get_orig_proj() API to get the src pixels.

	* app/paint/gimpcloneoptions.[ch]: added boolean "sample_merged"
	property.

	* app/tools/gimpclonetool.c: follow GimpClone's src_drawable ->
	src_pickable change.

	(gimp_clone_tool_button_press): set the paint_core's
	"use_saved_proj" boolean before chaining up.

	(gimp_clone_options_gui): add a "Sample Merged" toggle button.