# This is free and unencumbered software released into the public
# domain. To the extent possible under law, the author of this file
# waives all copyright and related or neighboring rights to it.

$(call include-once.,programs.mk)

XCF2PNG ?= xcf2png
ICONUTIL := $(call command-v,iconutil icnsutil)

PNGCRUSH ?= pngcrush
PNGCRUSHFLAGS ?= -brute -blacken -reduce -q
CRUSH.png ?= $(PNGCRUSH) $(PNGCRUSHFLAGS) -ow

%.png: %.xcf
	$(XCF2PNG) $< > $@

# First: xcf2png by default calls zcat rather than gzcat. This is
# totally always broken; non-GNU zcat forces a .Z extension on its
# input filename. So we can't rely on xcf2png's default behavior.
# Luckily it offers -Z for a custom decompression program.
#
# BUT: When Gimp saves a .xcf.gz (and related formats), it doesn't
# truncate the file, it just writes until it's done and closes, and
# whatever data was after that, is still after that. This is terrible
# because it means the file never shrinks, but it's still nominally a
# valid gzip file, according to http://www.gzip.org/#faq8.
#
# BUT: The suggestion to use gzip -q in the FAQ doesn't work for
# non-GNU gzip. It shuts up the 'warning,' yes, but it still exits
# with status code 1 (not even 2, like GNU gzip does for all
# warnings). It does write out the data perfectly well, at least.
#
# BUT (of course): The non-zero exit (somewhat reasonably) makes
# xcf2png barf and die before writing anything even though it got all
# the data it needs.
#
# So: 1) use gunzip, 2) manually feed it to xcf2png, 3) hope nothing
# is set to die based on pipe status, 4) hope that if the xcf data is
# truly busted xcf2png will do something helpful.
%.png: %.xcf.gz
	gunzip -c $< | $(XCF2PNG) - > $@

# https://korewanetadesu.com/make-icons.html
.SECONDEXPANSION:
%.icns: %.iconset $$(wildcard $$(@D)/$$*.iconset/icon_*.png)
	$(ICONUTIL) -c icns -o $@ $<

%.ico: %.iconset $$(wildcard $$(@D)/$$*.iconset/icon_*[0-9].png)
	convert -background transparent -colors 256 $(filter-out $<,$^) $@

find-iconsets = $(shell find $1 -type d -name '*.iconset')
find-xcfs = $(shell find $1 -type f -name '*.xcf.gz' -or -name '*.xcf')

iconset>icons = $(1:.iconset=.icns) $(1:.iconset=.ico)
xcf>png = $(patsubst %.xcf,%.png,$(patsubst %.xcf.gz,%.xcf,$1))

pngcrush-stampprefix ?= $(stampprefix)
pngcrush-stampify = $(1:%.png=$(pngcrush-stampprefix)%.png.crushed)

$(pngcrush-stampprefix)%.png.crushed: %.png
	$(MKDIR) $(@D)
	$(CRUSH.png) $<
	touch $@