Generate Haskell bindings for GObject Introspection capable libraries.
Installation
To compile the bindings generated by haskell-gi, make sure that you have installed the necessary development packages for the libraries you are interested in. The following are examples for some common distributions. (If your distribution is not listed please send a pull request!)
Install Homebrew and install GTK+ and GObject Introspection:
brew install gobject-introspection gtk+ gtk+3
Ensure the path to libffi (probably /usr/local/opt/libffi/lib/pkgconfig) is in the PKG_CONFIG_PATH environment variable.
Windows
Please see here for detailed installation instructions in Windows.
Using the generated bindings
The most recent versions of the generated bindings are available from hackage. To install, start by making sure that you have a recent (2.0 or later) version of cabal-install, for instance:
$ cabal install cabal-install
$ cabal --version
cabal-install version 2.4.1.0
compiled using version 2.4.1.0 of the Cabal library
Here is an example "Hello World" program:
{-# LANGUAGE OverloadedStrings, OverloadedLabels #-}
{- cabal:build-depends: base, haskell-gi-base, gi-gtk == 3.0.*-}importqualifiedGI.GtkasGtkimportData.GI.Basemain::IO()
main =doGtk.initNothing
win <- new Gtk.Window [ #title :="Hi there" ]
on win #destroy Gtk.mainQuit
button <- new Gtk.Button [ #label :="Click me" ]
on button #clicked (set button [ #sensitive :=False,
#label :="Thanks for clicking me" ])
#add win button
#showAll win
Gtk.main
This program uses the new OverloadedLabels extension in GHC 8.0, so make sure you have a recent enough version of GHC installed. To run this program, copy it to a file (hello.hs, say), and then
$ cabal v2-run hello.hs
For a more involved example, see for instance this WebKit example. Further documentation can be found in the Wiki.
Translating from the C API to the haskell-gi generated API
The translation from the original C API to haskell-gi is fairly
straightforward: for method names simply remove the library prefix
(gtk, gdk, etc.), and convert to camelCase. I.e. gtk_widget_show
becomes
widgetShow
in the module GI.Gtk (provided by the gi-gtk package).
For properties, add the type of the object as a prefix: so the sensitive property of GtkWidget becomes widgetSensitive in gi-gtk. These can be set using the new syntax, as follows:
b <- new Button [widgetSensitive := True]
or using set after having created the button
b `set` [widgetSensitive := False]
Alternatively you can use setWidgetSensitive and friends to set properties individually if you don't like the list syntax.
Finally, for signals you want to use the onTypeSignalName functions, for example onButtonClicked:
onButtonClicked b $ do ...
This is the basic dictionary. Note that all the resulting symbols can be conveniently searched in hoogle.
There is also support for the OverloadedLabels extension in GHC 8.0 or higher. So the examples above can be shortened (by omitting the type that introduces the signal/property/method) to
b <- new Button [#sensitive := True]
on b #clicked $ do ...
#show b
It should be rather easy to generate bindings to any library with gobject-introspection support, see the examples in the bindings folder. Pull requests appreciated!
Higher-Level Bindings
The bindings in haskell-gi aim for complete coverage of the bound APIs, but as a result they are imperative in flavour. For nicer, higher-level approaches based on these bindings, see:
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