Gtk2Hs

Keith Hanna is reworking his interactive, document-centered Haskell environment Vital in Haskell. The project is now called Pivotal and is written entirely in Haskell, using Gtk2Hs for the GUI. The idea of the project is to have an interactive environment like a spreadsheet, but instead of entering untyped formulae over very basic types, all elements of the spreadsheet are well-typed Haskell expressions. This does not only give type-safety, but also allows for much more interesting data types like trees or even pictures. Check out the home page for some stunning examples!

To mark the end of Paolo Martini’s project to add support for the cairo vector graphics library we are pleased to announce a special “tech preview” release of Gtk2Hs including Paolo’s contributions.

Here’s a screenshot from a demo program Paolo and others wrote to show off the combination of Haskell, cairo and Gtk+.

You can see more of his latest screenshots in his blog.

As of version 2.8, Gtk+ now depends on cairo and uses it for much of it’s drawing. It is a great advance over Gtk’s previous drawing API. The cairo website describes it thusly:

Cairo is a 2D graphics library with support for multiple output devices. Currently supported output targets include the X Window System, win32, and image buffers. Experimental backends include OpenGL (through glitz), Quartz, XCB, PostScript and PDF file output.

Cairo is designed to produce consistent output on all output media while taking advantage of display hardware acceleration when available (for example, through the X Render Extension).

The cairo API provides operations similar to the drawing operators of PostScript and PDF. Operations in cairo including stroking and filling cubic Bézier splines, transforming and compositing translucent images, and antialiased text rendering. All drawing operations can be transformed by any affine transformation (scale, rotation, shear, etc.).

We encourage anyone who has Gtk+ 2.8 installed to give this Gtk2Hs release a try and to experiment with using the cairo drawing API. Bug reports and cool screenshots will be gratefully accepted.

Download: gtk2hs-0.9.9.5.tar.gz

The release includes some demos showing how to use cairo in a stand alone fashion to produce PNG image files and also demos showing how to use the cairo api for drawing in a Gtk+ GUI (both real-time and non-real-time). There is also some preliminary reference documentation available.

This release is not intended for packaging for distros. The next ordinary release will of course retain the cairo support. It is intended that the cairo package will eventually be distributed separately since it is useful in non-GUI programs too.

This project was undertaken by Paolo as part of Google’s Summer of Code programme. In our opinion his project has been a success and so we would like to recommend to Paolo’s official mentor at Google and the judges that he be counted amongst the successful SoC programme participants and awarded the full project grant.

A new release for Gtk2Hs, namely version 0.9.9 is now available. This is a bug-fix release which is meant to fix various issues in the 0.9.8 release. Note further that the next release might be 0.9.10 and not necessarily 1.0.0. I apologise for my bad numbering scheme.

The tarball is available from at Sourceforge. The md5 checksum is 3276545190248d40c683cd42f51a1b6e.

Changes since 0.9.8:

• many documentation fixes
• documentation builds with the new haddock 0.7
• fixed an intolerant parser in c2hs, the C header-file scanner
• fixed segfaults when disconnecting signal handlers
• fixed segfaults in signals that pass TextIters
• add Pixmap from Gdk (not gtk_pixmap which is deprecated)
• added ChildAttributes to all containers
• minor fixes to our Makefile

Please report any problems with this release to our emailing list.

We are very pleased to announce that Paolo Martini’s project proposal to add support for the new cairo vector graphics library to Gtk2Hs has been selected to receive a grant in Google’s Summer of Code programme. This will make it possible to create GUIs in Haskell that take advantage of cairo’s sophisticated vector graphics capabilities and its high quality display and print output.

Paolo now has until the beginning of September to complete the project and receive the full $4500 grant. I know everyone will join me in wishing him the best of luck! Paolo is maintaining a blog about his project (and there is an rss feed).

We would also like to thank Google for recognising the importance of supporting projects like Gtk2Hs and hscairo that aim to make Haskell an even more versatile programming system.

Read on for Paolo’s full project proposal…
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