Development [LWN.net]

Developing applications "Quickly"

September 9, 2009

This article was contributed by Nathan Willis

Quickly is a new utility to simplify Linux application development by bootstrapping repetitive project setup, user interface, packaging, and release chores. It targets both new application developers and those who simply want to speed up recurring tasks. Quickly is a product of the Ubuntu project, but is flexible enough to be used in other distributions and for other types of tasks — the real power of Quickly lies in the templates that automate different aspects of project configuration and maintenance.

An application built using Quickly has no dependency on Quickly itself, said developer Didier Roche, "there is no Quickly runtime or base class library." The goal, he said, is to speed up the process for regular developers and help new developers get past the barrier of deciding which tools and approaches to use.

It can be difficult to get into GNU/Linux programming as there are a whole bunch of available technologies. Let's think about using GTK/QT, language, which library do I need? Add to this some tools decisions like the IDE, the VCS, hosting the project, etc. Too many choices kills the choice itself. [...] For instance, learning Debian packaging just to create a package to share with people can be tedious. Quickly (with ubuntu-project template) does it for you. Consequently, opportunistic developers can focus only on precise things and do it quickly, easily and right!

Canonical's Rick Spencer came up with the initial idea for Quickly after a series of false starts with missing documentation — including the deprecated tool libglade that did not point him towards its replacement gtkbuilder — and packaging guides that were so generalized that they provided little concrete help:

It took me a long time and a lot of digging to put together a set of tools for myself that worked for me. [...] This was partly due to the fact that there was no definitive source of information, or any credible expert. So threads in Ubuntu Forums where newcomers asked "how do I write an app for Ubuntu" get a pile of different options, and no way to know what is best. I very much wanted to solve this problem, and create a pipeline that made it easy to go from conceiving an app to have people using it.

The latest version of Quickly is 0.2.2 and is packaged only for Ubuntu 9.10, in which it is slated to be part of the official release. The authors note, however, that it could easily be packaged for Ubuntu 9.04 or for other distributions. Quickly is a command-line only tool that developers can use to execute discrete steps of the form:

    quickly command [options]

It has commands that create a new project, start an editing session, package it, make a public release, and so on.

Most of these commands are defined in a template tailored to a specific scenario; running "quickly commands" will list the built-in commands and those associated with each installed template. So far, the only released template is ubuntu-project, which automates working with Ubuntu-compatible code (using Bazaar for version control, Debian packaging, and Launchpad.net Personal Package Archives (PPA) for releases).

In addition, the ubuntu-project template makes what Roche called "opinionated choices" for the tools and technologies used by the new application: using Python for the language, PyGTK for the user interface, Glade for the UI design, Gedit for the editor, and Desktop CouchDB for (optional) data storage. Using the template's project creation routines to start a new project, Quickly creates a subdirectory for the project and set of skeleton files, including necessary Python and Glade files, plus auxiliary icon and licensing files. Quickly also creates Python classes to encapsulate basic windows and dialogs, and a separate Glade file for each class and window. These decisions are designed to make it simple to edit the application with Quickly, even though they might not be the design choices other programmers would make.

Example Quickly usage

The Ubuntu wiki features a basic tutorial on writing code with Quickly, and Roche has started a series of blog entries to document its usage and options. On August 31, Roche and Spencer hosted an IRC talk during Ubuntu Developer Week that delved into further detail.

The process starts by running:

    quickly create ubuntu-project myapp

Quickly then creates a ./myapp directory, and fills it with:

    bin/
    Copyright
    data/
    myapp/
    myapp.desktop.in
    setup.py

The Python files are placed in myapp/myapp, and the Glade files in myapp/data. After that, the developer must cd into the myapp directory. From there, quickly run will launch the new application, quickly edit will open the key Python files in Gedit, and quickly glade will open the UI files with Glade. Because the focus of the ubuntu-project template is on graphical applications, a quickly dialog command is available to create a new dialog window and associated class in Glade and Python.

Running quickly save will save the code to Bazaar, quickly license some_license will add license headers, and quickly package will calculate dependencies and generate a .deb package. Public releases are made with quickly share and quickly release. Both commands require the user to have a working account on Launchpad.net, complete with a PPA. The difference between the two commands is that share does not assign a version number or allow for a change log; release automatically increments version numbers, although they can be overridden.

Quickly design: core and templates

At its core, Roche explained, the quickly tool itself is essentially a parser and command processor. It checks context (for example, whether the working directory is a Quickly project directory), provides command completion, help, and a few low-level hooks, but most of the logic resides in the templates. Templates are written in Python, and although there is no documentation for template writing available yet, interested parties can browse the code used in the ubuntu-project template, which is installed by the package at /usr/share/quickly/templates/ubuntu-project.

Roche said that the Quickly team decided to separate as much of the "intelligence" as possible from the quickly core in order to make it more useful. "If anyone wants to make templates for other platforms, we would gladly merge those into our project," he said, perhaps separating Quickly templates into its own subproject from Quickly Core. "We would love to see, for instance, a fedora-project template, gnome-project one, plasmoid-project, [or a] zeitgeist-plugin."

Quickly even makes it simple to duplicate an existing template in order to customize it; the built-in command:

    quickly quickly template

creates a duplicate. The user can then modify the new template for use with other editors, other version control systems, or make more substantial changes without starting from scratch. "If someone likes the ubuntu-project template but doesn't agree on, let's say, couchdb but prefers gconf, he is able to create his own template based on ubuntu-project with $ quickly quickly ubuntu-project ubuntu-project-with-gconf and then hack in ~/quickly-templates/ubuntu-project-with-gconf/ to tweak what interests him," said Roche.

Quickly's core/template separation means that it is not limited to standalone GUI Linux application development. As the project's Launchpad page states, developers could easily create a template to kick-start creation of a conforming plugin for a specific application, for working with rendering systems like LaTeX, or for non-coding projects like documentation tasks.

As additional templates are written by Quickly users, Roche said, the team will coordinate with template authors to see what shared functionality deserves to be rolled up into built-in commands. Regardless of the task, some operations like file upload are generic enough for reuse. Quickly's Launchpad access is one such example; it began as part of the ubuntu-project template, but is now accessible to other template authors through Quickly's core — abstracting sign-in, reconnections, and other tasks.

Quickly in practice

Quickly is on track to ship with Ubuntu "Karmic Koala" 9.10, though Spencer said he does not know of any official Karmic applications written with Quickly. A few developers have started using the package to build small applications; Jono Bacon blogged about his use of Quickly while working on a tool for managing Amazon Kindle content, and Bryce Harrington has started developing a GUI front-end to Quickly — using Quickly itself.

Roche said that the near-term plans for the ubuntu-project template include adding some important features like GPG and SSH key creation for use with package signing and Launchpad upload. The team is also interested in adding new templates, including an ubuntu-game template that incorporates PyGame, and a gedit-plugin template that would demonstrate Quickly's applicability for application-specific plugin project development.

In the long term, Roche said that Quickly should be able to scale up to large projects in addition to the modest single-developer examples shown so far. It already supports concurrent Bazaar access, but the ubuntu-project template does not support Launchpad's "teams" collaboration feature because it is not accessible via the Launchpadlib library. Nevertheless, he said, the Quickly team is actively working on the issue and hopes to be able to tackle it in the future.

An early review of Quickly at Ars Technica compared it to Rails, which also uses a command-line to automate set-up for non-command-line projects. Readers responded that it also bears similarity to Django and Maven project creation, but it may be a first for desktop applications. Although, as Roche said, nothing about Quickly's core or its templating system limit it to desktop application development. Any repetitive task could be sped up by being adapted into a Quickly template; which templates the world sees depends entirely on who picks up Quickly and experiments with it.

Comments (10 posted)

System Applications

Audio Projects

alsa-lib 1.0.21a released

Version 1.0.21a of alsa-lib has been announced. "I made a quick release 1.0.21a of the alsa-lib package to fix regression for the configuration parsing (makes some device names unavailable)."

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Example Quickly usage

Quickly design: core and templates

Quickly in practice

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