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1 Overview

This page is intended to provide information for those wishing to work on the wxHaskell library, specifically creating and maintaining an environment in which to do so.

2 Obtaining wxWidgets

Firstly, see Getting wxWidgets and Building wxWidgets.

Note that wxHaskell is currently between wxWidgets 2.8 and the development 2.9 release, so it pays well to ensure new code will work with both versions. It is possible to safely co-habit two version of wxWidgets. When you do wxHaskell will build against whichever version is returned by wxconfig --version, on Linux you can change which version you build wxHaskell against by follow steps similar to this (this should be easier):

$ wx-config --version
$ whereis wx-config
wx-config: /usr/local/bin/wx-config
$ ls -l /usr/local/bin/wx-config
lrwxrwxrwx 1 root root 41 2011-09-14 21:20 /usr/local/bin/wx-config -> /usr/local/lib/wx/config/gtk2-unicode-debug-2.8
$ sudo rm /usr/local/bin/wx-config
$ sudo ln -s /usr/local/lib/wx/config/gtk2-unicode-2.9 /usr/local/bin/wx-config
$ wx-config --version

3 Building and testing wxHaskell

Firstly, see Source Release, however it is recommended that you do the following, instead of following the instructions there to build each component:

Use Cabal-dev to isolate your development code from stable wxHaskell packages you may have obtained from Hackage. You can then install your development version of wxHaskell into a separate Cabal-dev package database (which will be under ./cabal-dev/packages-7.0.3.conf/). To do this enter the root wxHaskell directory (the one you obtained with darcs from and enter the following:

cabal-dev install ./wxdirect ./wxc ./wx ./wxcore


  • Previously this page suggested using add-source, but packages added in such a way will not be recompiled when the source given is changed, this is discussed in the "Using a sandbox-local Hackage" section.
  • If changes are made to wxdirect, the shell PATH environment variable should contain cabal-dev/bin before other locations where a(nother) wxdirect executable can be found.

You may then build against your development install thus:

ghc -package-conf /path/to/wxhaskell/cabal-dev/packages-7.0.3.conf/ --make MyTestCode.hs

4 Wrapping new wxWidgets functionality

Note: Inspiration for this comes from this email.

4.1 Purpose of files which will need to be updated

Although the specific modifications required depends on the complexity of the wxWidgets functionality you are wrapping, this list serves to document the relationship between the files and what purpose they serve.

'High' level Haskell wrapper. You place constructors which are property-aware here. In most respects this is straightforward except that you need to work out what instances are appropriate to a your new functionality. You may want to look here for some more information about implementing Attribute instances.
This creates the correct type witnesses to map the class Hierarchy.
This is basically where you need to put the declarations for C++ method wrappers.
Your Haskell event handler code goes here. You need one function which reacts to events, which accepts an event handler as a parameter and a function which will fetch your event handler (you need this mostly in case you want to hook a further event handler which doesn't kill the one already present).
Implementations of the wrappers. The old eljXXX naming convention for these files really isn't necessary any more. I'd suggest calling the implementation mynewfunctionality.cpp or something like that.
Constructs functions for getting control pointers out of window hierarchies created from XRC files.
Wrap up event values as functions. I tend to do this instead.
Another way of wrapping up event values as functions. (Jeremy: I don't tend to do this, and I don't think anyone has for years.).
Ensure you add mynewfunctionality.cpp to c-sources in ./wxcore/wxcore.cabal