Hi there, I've recently been doing some work on packaging GUIs for OS X, and I'm writing to ask: a) for assurance that the approach taken is sensible and consonant with the Tao of Cabal's, and b) a (probably simple) question about making this work nicely cross- platform, c) for any advice anyone wants to give. :-) Here's the background: For a GUI to run nicely under OS X, it needs to be packaged into an application bundle, which is a folder containing the executable binary and any related resources (such as libraries, icons, etc.) in a designated structure, and marked as an app bundle via a tool called Rez. Without being in such a bundle, the executable runs without its icon, and doesn't respond to user actions. Historically, this has been solved (in a minimal fashion) by a script called macos-app (see http://www.haskell.org/haskellwiki/WxHaskell/MacOS_X) , which is included in the wx distribution. This works, but doesn't integrate very prettily into a cabalised build process. (BTW, are there any gtk2hs/OS X users out there? My (limited) experience suggests that "bare" gtk2hs executables work OK, but don't get focus automatically and of course lack nice icons. Thus, this work could be of use to gtk2hs users as well?) Recently, Eric Kow did some work towards replacing macos-app with equivalent Cabal-based machinery, and I've now polished that up a bit, cabalised it, and made it public on github (http://github.com/gimbo/osxSetup.hs ). I _haven't_ released it on hackage yet, but will do when I'm sure it's going in the right direction. So: - We have a package (cabbage?): cabal-macosx - It exports a single module: Distribution.MacOSX - That exports a post-build hook for creating the app bundle, as well as data types for customisation info (e.g. the icon). and at present that's it. Installation isn't handled yet: "runghc Setup install" just copies the bare executable, which doesn't run properly - so I need to fix that. (Eric's original version did the work upon installation, but I needed it at build-time, so I moved it.) [Another thing I'd like to add: app bundles can carry their own copies of shared libraries, which makes distribution much simpler (you just publish the whole bundle, and it works, standalone). To support this, I'll need to add some a pre-build hook copying them into the right place (and so, building the app bundle will happen even earlier), and also insert some linker flags (Cabal can handle this?).] OK, so that's the picture. Reasonable so far? Now comes the question: Obviously, cabal-macosx is only _really_ a dependency when building on OS X. How can I (indeed, should I?) remove this depedency for other platforms? For example, consider http://github.com/gimbo/osxSetup.hs/blob/master/examples/wxHello/wxHello.cab... - here, I could make cabal-macosx platform-dependent using, say: if os(darwin) Build-Depends: base >= 3 && < 5, cabal-macosx, wx else Build-Depends: base >= 3 && < 5, wx but there is then still an "import Distribution.MacOSX" in Setup.hs (eg http://github.com/gimbo/osxSetup.hs/blob/master/examples/wxHello/Setup.hs) , so build will still fail on other platforms. Is the right way to handle this: a) Just demand cabal-macosx on all platforms, and do the check in Setup.hs (as in the above example)? b) Build platform checks into Setup.hs? I don't even know if that's possible: a platform-specific import? c) Something else? All advice and comments appreciated - thanks for reading this far! Best, -Andy -- Andy Gimblett http://gimbo.org.uk http://www.cs.swan.ac.uk/~csandy/