GTK+ application support integrated into Maliit mainline

GTK+ application support for Maliit input methods has existed for a long time, but up until now it has lived in separate repositories. This has been inconvenient for users and for developers, and was the major cause for it to not be on the same level as the Qt support. This has changed as the GTK+ support has now been merged into the maliit-framework repository, and along side the Qt support. Maliit 0.80.8, which was released yesterday, contains these changes.

Maliit running on WeTab with Fedora 15, showing QML reference plugin and GTK+ application

Two implementations existed for Maliit GTK+ support. One was written by Javis Pedro as part of a Google Summer of Code project for MeeGo in 2010. His blog has several posts on the topic. The other implementation was maintained by Raymond Liu (Intel). This is the implementation shipped in Meego Netbook, and the one improved by Claudio Saavedra (Igalia) as part of the GTK+ on MeeGo project. It was also the only one that was updated to work with the DBus connection changes that was done quite some time ago, and supporting both GTK 2 and 3. For these reasons this was the implementation integrated into mainline Maliit.

Once the code was integrated, improvements soon followed. The application now correctly reconnects to server, and make install will automatically update the GTK+ input module cache on Ubuntu, thanks to Łukasz Zemczak (Canonical), and on Fedora. This means GTK+ application support will work out of the box, no twiddling needed.

While this is a huge step in the right direction, the GTK+ support is not as good as for Qt yet. Javis Pedros implementation has features that does not exist in mainline, so code/principles can hopefully be reused from there to implement these. This includes custom toolbars and attribute extensions, and content type hints for text entries. Other features looks hard to implement due to limitations/differences in the input context plugin architecture found in GTK+, and will probably need work in GTK+ itself to solve.

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Making GEGL easier to use in graphical applications

So, in the last couple of months I’ve been working a bit on GEGL. Some of the work has already been covered by LWN, so I guess it is time that I blog about it…

GEGL is a generic image processing library which is used by applications like GIMP, (and in the future maybe MyPaint and DarkTable). It provides applications with a graph based image processing backend that can do non-destructive processing of high-bitdepth images, among other things.

One of the problems that I think has been limiting adaptation of GEGL has been the entry barrier to starting to use it in a graphical application. While GEGL provides the image processing backend, it did not provide good and easy ways of displaying the output on screen. Now it does!

GTK+, Clutter and Qt integration libraries

Some code for integrating GEGL in GTK+ based applications has existed in the GEGL tree for a long time, but it was not well maintained and there was no public API. After brushing up the code to use Cairo for rendering and to support both GTK+ 2 and 3, it was split out to a separate library and repository: gegl-gtk. This library now provides a GtkWidget for displaying the output of a node in the GEGL graph, with basic support for scaling and translations. Any change in the GEGL graph will be reflected in the view widget. This makes it trivial for applications using a GTK+ based user interface to get started using GEGL, see for instance the provided examples in C or in Python.

The same functionality is provided for Clutter based user interfaces by gegl-clutter in form of a ClutterActor. This code was previously available as clutter-gegl, but has now been renamed and moved to be a part of the GEGL project, and is maintained by Øyvind Kolsås. Example code in C.

Last but not least, gegl-qt was created to serve the needs of applications using Qt based user interfaces. The different widget systems (QWidget-, QGraphicsWidget- and QML-based) are all supported. In addition to the features currently available in the GTK+ and Clutter versions, the Qt view widgets also support auto-scaling and auto-centering. Python bindings via PySide is planned, but blocking on a PySide issue at the moment.

A pretty boring screenshot showing two QWidget based examples (code: 1, 2) for transformations:

Artwork: “Wanted“, speedpainting by David Revoy

The first stable release of gegl-qt and gegl-gtk will hopefully be available soon. The list of tasks can be found in the README files.

Display operations

In GEGL, image processing is described as a graph of operations. “gegl:display” and “gegl:gtk-display” operations existed in the gegl tree, and by attaching one of these to a node in the graph one could display the output of the graph at the given node in a window . Such display operations are useful for applications that just want to show the output of a graph without having to use a GUI library directly.

The problem was that both of these operations were optional, so applications could not rely on this functionality to be present. This is solved by letting the “gegl:display” operation be a meta-operation, which uses other operations as a handler to actually display the output. Such display handler operations are now provided by gegl (optional, using SDL), gegl-gtk (using GTK+) and gegl-qt (using Qt). In addition a fallback operation that will export a PNG file and launch an external application to display it will be provided in GEGL.

More to GEGL stuff to come soon, hopefully.

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Glom is an application that lets you design database systems, including user interface. It can be run as an ordinary application, and will set up and run a the database server for you automatically. But if you want to set up a shared instance, where several users connect with Glom to the same database, you typically want your database server on a dedicated server. And this can be a bit tricky to set up. So, glom-postgresql-setup was born; A dead-simple utility application to set up a PostgreSQL server for use with Glom. Like Glom, it is written in C++ using Gtkmm.

glom-postgresql-setup lets you to create a database user, and set up the PostgreSQL configuration to accept connections from external IPs. The UI is just a dialog with two fields and two buttons, dead-simple indeed. For now the application requires to be launched with superuser privileges, but before we encourage use of this tool we will of course implement proper privilege escalation using PolicyKit.
It would also be nice to be able to install and start the PostgreSQL server as well, but currently that is not so easy to do in a cross-distro way. Hopefully packagekit and systemd will help solve that, eventually.

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