Proper DMG support on macOS.

Previously `make install` on macOS created TuxPaint.dmg, but it was a
simple disk image.

Now TuxPaint.dmg is formatted as one would expect from any other macOS app,
with a Tux folder icon, symlink to the /Applications folder, and a
background image with an arrow.

.gitignore

@@ -11,3 +11,4 @@ TuxPaint.app
 TuxPaint.dmg
 *.dylib
 *.dylib.dSYM
+.DS_Store

Makefile

@@ -482,7 +482,8 @@ install:	install-bin install-data install-man install-doc \
 	@echo
 	@if [ "x$(OS)" == "xosx" ]; then \
 		echo "All done! Now you can double click $(BUNDLE) to run the"; \
-		echo "program!!!"; \
+		echo "program!!! TuxPaint.dmg has also been created for"; \
+		echo "distribution."; \
 		echo; \
 		echo "For more information, see $(DOC_PREFIX)/README.txt"; \
 	else \
@@ -591,7 +592,7 @@ clean:
 	@-rm -f templates/.thumbs/*.png
 	@if [ -d templates/.thumbs ]; then rmdir templates/.thumbs; fi
 	@-if [ "x$(BUNDLE)" != "x" ]; then rm -rf $(BUNDLE); fi
-	@-rm -f TuxPaint.dmg; rm -rf magic/*.dSYM
+	@-rm -f TuxPaint.dmg temp.dmg; rm -rf magic/*.dSYM
 	@echo
 
 # "make uninstall" should remove the various parts from their
@@ -1013,7 +1014,7 @@ install-man:
 	@chmod a+rx,g-w,o-w $(MAN_PREFIX)/man1/tp-magic-config.1.gz
 
 
-# Install the support files for macOS application bundle
+# Install the support files for macOS application bundle and create DMG
 .PHONY: install-bundlefiles
 install-bundlefiles:
 	@echo
@@ -1026,8 +1027,9 @@ install-bundlefiles:
 	@install -m 644 macos/Info.plist $(BUNDLE)/Contents
 	@install -m 644 macos/tuxpaint.icns $(BUNDLE)/Contents/Resources
 	@custom/macos.sh
-	@echo "...Creating TuxPaint.dmg..."
-	@hdiutil create -volname "Tux Paint $(VER_VERSION)" -srcfolder $(BUNDLE) -ov -format UDBZ -o TuxPaint.dmg
+	@echo
+	@echo "...Creating DMG Distribution File..."
+	@custom/macos-mkdmg.sh
 
 
 # Build the program!

custom/macos-mkdmg.sh

@@ -0,0 +1,45 @@
+#!/bin/sh
+
+BUNDLE=TuxPaint.app
+TEMP_DMG=temp.dmg
+TEMP_DMG_SIZE=`expr \`du -sm "$BUNDLE" | cut -f1\` \* 15 / 10`m
+FINAL_DMG=TuxPaint.dmg
+VOLNAME="Tux Paint"
+ICON="macos/tuxpaint.icns"
+BACKGROUND="macos/background.png"
+
+
+echo "   * Creating the temporary image..."
+hdiutil create "$TEMP_DMG" -ov -fs HFS+ -size "$TEMP_DMG_SIZE" -volname "$VOLNAME" \
+&& VOLUME=`hdiutil attach "$TEMP_DMG" -nobrowse -noverify -noautoopen | grep Apple_HFS | sed 's/^.*Apple_HFS[[:blank:]]*//'` \
+|| exit 1
+
+echo "   * Adding the image background..."
+mkdir "$VOLUME/.background" \
+&& tiffutil -cathidpicheck "$BACKGROUND" -out "$VOLUME/.background/background.tiff" \
+|| exit 1
+
+echo "   * Setting the folder icon..."
+cp "$ICON" "$VOLUME/.VolumeIcon.icns" \
+&& xattr -wx com.apple.FinderInfo '00 00 00 00 00 00 00 00 04 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00' "$VOLUME" \
+|| exit 1
+
+echo "   * Copying the contents..."
+ln -s "/Applications" "$VOLUME" \
+&& cp -a "$BUNDLE" "$VOLUME" \
+&& cp -a "macos/DS_Store" "$VOLUME/.DS_Store" \
+|| exit 1
+
+echo "   * Configuring the folder to open upon mount..."
+bless --folder "$VOLUME" --openfolder "$VOLUME" \
+|| exit 1
+
+echo "   * Unmounting the temporary image..."
+hdiutil detach "$VOLUME"
+
+echo "   * Creating the final image..."
+hdiutil convert "$TEMP_DMG" -ov -format "UDBZ" -imagekey "zlib-level=9" -o "$FINAL_DMG"
+
+echo "   * Deleting the temporary image..."
+rm -f "$TEMP_DMG"
+