2004-01-13  Michael Natterer  <mitch@gimp.org>

	* app/base/gimphistogram.[ch]: renamed gimp_histogram_nchannels()
	to gimp_histogram_n_channels().

	* app/core/gimpdrawable-histogram.c: removed silly double negation
	logic. Cleanup.

	* app/widgets/gimphistogrameditor.c
	* app/widgets/gimphistogramview.c: adjust the GimpHistogramChannel
	for GRAYA images to make sure we pick alpha from the right slot.

	* app/tools/gimpcurvestool.c
	* app/tools/gimplevelstool.c: removed the same hack here and call
	gimp_histogram_view_set_channel() with the correct enum value.

	* tools/pdbgen/pdb/color.pdb (levels, curves, histogram): fiddle
	with enum values here too so GRAY* drawables produce the correct
	results.

	Fixed precondition checks and set "success" in a uniform way all
	over the place.

	Use gimp_drawable_calculate_histogram() instead of duplicating its
	code here.

	(started with a patch from Pedro Gimeno. Fixes bug #109078)

	* app/pdb/color_cmds.c: regenerated.