Archive for the ‘Announcements’ Category

Gtk2Hs 0.11.0 released

Tuesday, May 25th, 2010

Today, we’re proud to announce the very first release of Gtk2Hs that comes in cabal packages. This means that installation is easier on all systems in that only the Gtk+ libraries have to be installed before a simple ‘cabal install gtk2hs-buildtools’ and ‘cabal install gtk’ do the rest of the job. This even holds for Windows! See the install instructions for detailed information.

This release probably still has some rough corners, but we feel that a cabal release is due and hope that it’s already usable!

Axel, on behalf of the Gtk2Hs developers

Cabalized version of Gtk2Hs now up for testing.

Wednesday, April 21st, 2010

Dear all,

the repo at now contains a cabal version of Gtk2Hs, well, at least of the core packages glib, cairo, pango and gtk. In the future the package gio should be part of this set as well. All other add-on libraries, however, are likely to move into their own darcs repositories. During this transitional period it is not possible to build the other libraries but I encourage people to get the new cabal version using

darcs get

and to add cabal files to the any of these add-on libraries. Notes on that below (”Creating a cabal file for a Gtk2Hs add-on library”).

Observe that updating your current darcs repo of the previous version of Gtk2Hs is not possible since I had to obliterate several patches in order to merge changes. Furthermore, there are quite a few patches in the previous repository that added a lot of new functions but which need further review. These patches have been merged into the new cabal version but for now remain in a separate repository which can be accessed at .


The Gtk2Hs libraries need additional build tools. These live in tools/ and can be configured and installed in the usual Cabal way. The three tools have awkward names starting with gtk2hs and are thus not likely to clash with other programs. If you install as –user, then you need to add ~/.cabal/bin to your path. (I’ve filed a bug that cabal should look in it’s own /bin directory for build utilities. )

When configuring the gtk package, the cabal file will look for Gtk+ 2.20 which you most likely don’t have. You need to specify -f-gtk_2_20 for Gtk+ 2.18 and -f-gtk_2_20 -f-gtk_2_18 for Gtk+ 2.16 and so on. (I have filed a feature request that Cabal should be able to infer the best possible choice of flags for pkg-config requirements. )

When compiling the Setup.hs program, you will see a warning that the Cabal version is guessed. If compilation succeeds, this warning can be ignored. (Cabal should really define CPP macros with it’s version when it builds Setup.hs, see )

Creating a cabal file for a Gtk2Hs add-on library

The Setup.hs file for a Gtk2Hs add-on library will be the same as that for glib, pango, cairo and gtk. Thus, simply copy one of these files to the subdirectory of the add-on library you wish to cabalize. Even better: replace all Setup.hs files by a hard link. It would be good if all setup files remain identical.

The cabal file for a new add-on library is pretty much standard. You need to depend on gtk-0.10.5 and possibly others such as glib-0.10.5. Note that the core packages glib, cairo, pango, gtk will all evolve with the same version.

The category for the core files at the moment is Graphics or Rendering. Note that you could use cairo and pango to create PDF or PNG files without ever touching any GUI stuff. Thus, the category for the other libraries need to be Graphics. It would be interesting to hear if people think that Gtk2Hs should have it’s own category or not.

There are two sets of special fields: x-Types-XXX to build a type hierarchy and x-Signals-XXX to build a callback definitions. You should only need the former. If your package requires callback with arguments not provided in the gtk package then we need to add them to the Gtk package. This is unfortunate, but the infrastructure is not yet adjusted to build package-specific callback definitions.

As to the type hierarchy: The type generator comes with a list of built-in types is located in tools/hierarchyGen/hierarchy.list .
Any of the x-Type-XXX directives are basically specifying arguments to be passed to the type-file generator. You can find out about the arguments it takes by running ~/.cabal/bin/gtk2hsTypeGen without arguments.

For starters, you need to specify where the Types module should live. Use the following two directives:

x-Types-Files: Graphics/UI/MyLib/Types.chs
x-Types-ModName: Graphics.UI.MyLib.Types.chs

Now there are two variants on how you might want to use the type generator:

(a) Building an add-on library that relies only on glib, cairo and/or pango. Specify:

x-Types-Forward: *System.Glib.GObject

(b) Building an add-on library that depends on the gtk package. Specify:

x-Types-Forward: *System.Glib.GObject *Graphics.UI.Gtk.Types
x-Types-Destructor: objectUnrefFromMainloop

The deeper meaning of the different is that any library building on Gtk is assumed to be GUI library that interacts with X11 or Win32 and, thus, any object that is destroyed may release an X11 or Win32 resource which, in turn, may not be done from arbitrary threads. The above option ensures that the freeing happens in the Gtk+ main loop which ensure that the objects are freed from the correct thread. Libraries building on glib, cairo and pango do not interact with X11 or Win32 nor do they have a main loop. Here, freeing objects is done directly by GHC’s garbage collector.

One note for gstreamer: This package requires two type hierarchies. This is currently not supported by the Setup.hs script but it should not be too hard to add this.

The files of each individual add-on libraries are often .chs, .chs.pp and .hsc files. No changes are normally necessary for .chs and .hsc files. Since Cabal is not able to run more than one pre-processor on a file (it cannot handle several extensions) every .chs.pp file must be renamed and a {-# LANGUAGE CPP #-} directive must be prepended to the file. I used the following bash script to do this:

#! /bin/bash
NEW=`dirname $1`/`basename $1 .pp`;
rm -f $NEW
darcs mv $OLD $NEW
mv $NEW “$NEW”.tmp
echo “{-# LANGUAGE CPP #-}” > $NEW
cat “$NEW”.tmp >> $NEW
rm “$NEW”.tmp

(save this in In order to convert all files in the library myLib do:

find myLib -name “*.chs.pp” -exec ./ “{}” \;

in the directory containing myLib.

You need to add any other language extension to each individual file that need it (e.g. replace “CPP” with “CPP, ScopedTypeVars” or whatever). Note that any file that is now called .chs and has a CPP directive in its first line is now run through cpp by our home-grown c2hs variant (making it even more incompatible with the mainstream c2hs).

A note on the new Setup

For those who are curious how the Gtk2Hs Setup.hs differs from Simple, the changes are as follows:

- during configuring, the signal and type files are generated. Both only happen if the appropriate x-Signals- and x-Types- fields are specified in the cabal file.

- our home grown c2hs is run on .chs files instead of the mainstream one

- our c2hs files produces .chi files that must be available to other packages, just like .hi files. These .chi files are therefore copied during installation of files

- before pre-processing the .chs files, we calculate the dependencies between the files and rearrange the list of files to build such that the dependencies are honored

That’s it!

Any feedback appreciated,
Axel (on behalf of the Gtk2Hs developers)

Compiling with ghc 6.12

Monday, January 18th, 2010

Duncan posted a patch that allows compilation of Gtk2Hs with ghc 6.12. However, you need to specify –disable-split-objs option when running configure as ghc 6.12 puts object files in directories where our Makefile does not expect them.

Writing concurrent programs.

Wednesday, November 4th, 2009

A note of caution: Using Gtk2Hs together with the -threaded ghc is currently not supported. The reason is that GHC’s garbage collector might free Xlib or Win32 objects using an OS thread different to the one that is used to execute all other Gtk+ functions. The result will be a program that occasionally fails with an Xlib error or a crash on Windows. We are working on fixing this.

Note: this is all now fixed in the current darcs repository.