Practical GNOME Programming with Ruby FOSDEM 2004 Tutorial Laurent - - PowerPoint PPT Presentation

Practical GNOME Programming with Ruby

FOSDEM 2004 Tutorial

Laurent Sansonetti - lrz@gnome.org Nikolai Weibull - pcp@pcppopper.org

http://ruby-gnome2.sourceforge.jp

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Goal

Our goal is to demonstrate that Ruby is Useful to glue complex components together Mature enough for real GNOME development Sexy by developing a very, very simple audio player:

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TOC

Contents: The Ruby-GNOME2 Project User Interface Design Multimedia Design Implementation Questions

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TOC

Contents: The Ruby-GNOME2 Project User Interface Design Multimedia Design Implementation Questions

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The Ruby-GNOME2 Project

Since 2002 Current release: 0.8.1 Has 16 developers worldwide Supports 17 GNOME libraries Resources in English, and i18n in progress (French, Italian, and Japanese)

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The Ruby-GNOME2 Project

Supported libraries:

Name Implementation Status Tutorials? API Reference? Examples? ATK *** No No Yes GConf *** Yes Yes Yes GDK *** No Yes Yes GLib *** No No Yes GStreamer *** No Yes Yes GTK *** Yes Yes Yes GnomeCanvas *** No No Yes GtkGLExt *** No Yes Yes Libgda *** Yes Yes Yes Libglade *** No No Yes Libgnome *** No No Yes GdkPixbuf ** No No Yes GnomeVFS ** No No Yes Libart ** No No Yes Pango ** No No Yes GtkHtml * No No Yes GtkSourceView * No No Yes

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The Ruby-GNOME2 Project

RBBR (RuBy BRowser): Inspects classes/modules: Native stuff: methods, constants, ancestors, . . . GLib stuff: signals, properties, enum/flags, . . . Displays API reference (if exists) Shows GNOME stock items/icons Usable (HIG compliant) i18n (Belarusian, English, French, Japanese)

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TOC

Contents: The Ruby-GNOME2 Project User Interface Design Multimedia Design Implementation Questions

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User Interface Design

Glade is a GTK+/GNOME user interface builder. Glade can: generate source code (C/C++/Perl/.../Ruby) for the user interface: the bad generate an XML file (.glade) loadable by Libglade: the good crash: the ugly

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User Interface Design

Ruby/Libglade in action:

require ’libglade2’ engine = GladeXML.new(’my_project.glade’) do |handler_name| # connect the signal handler somewhere # we need to return a method reference lambda{ puts handler_name + " was called!" } end window = engine[’my_window’] # window is a Gtk::Window window.title = "My Application" button = engine[’my_button’] # button is a Gtk::Button button.text = "My Button" button.sensitive = false : :

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User Interface Design

Let’s play a bit with Glade!

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TOC

Contents: The Ruby-GNOME2 Project User Interface Design Multimedia Design Implementation Questions

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Multimedia Design

GStreamer is A multimedia framework A set of components (plugins) for input codecs (audio, video, . . . ) filters / processors

• utput

Network transparent Extensible Fast Still under heavy development

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Multimedia Design

GStreamer deals with pipelines. Pipelines are sets of elements Elements are sets of pads Pads are connection points between elements Elements are generally one of the following: A source - provides data A filter - tranforms data A sink - consumes data

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Multimedia Design

GStreamer pipeline overview:

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Multimedia Design

Pipelines are what we get after connecting elements in a sequence, much like connecting commands in a shell. We will discuss three pipelines: filesrc ! mad !

• sssink

filesrc ! spider !

• sssink

gnomevfssrc ! spider !

• sssink

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Multimedia Design

The filesrc ! mad !

• sssink pipeline consists of:

filesrc - provides data from a file on disk mad - decodes MPEG audio using libmad

• sssink - sends audio to soundcard using OSS

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Multimedia Design

Positive Simple, works very well Negative Can only decode files on disk Can only decode MPEG audio

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Multimedia Design

We can do better! The filesrc ! spider !

• sssink pipeline consists
• f:

filesrc - provides data from a file on disk spider - finds type of data and creates proper decoder

• sssink - sends audio to soundcard using OSS

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Multimedia Design

Positive Works for any kind of media type with audio data Works well in most cases Simple to set up Negative Can only decode files on disk Can fail to find type Can fail to find decoder Slower than using proper decoder immediately

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Multimedia Design

We can still do better! The gnomevfssrc ! spider !

• sssink pipeline

consists of: gnomevfssrc - provides data from an URL using GnomeVFS spider - finds type of data and creates proper decoder

• sssink - sends audio to soundcard using OSS

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Multimedia Design

Positive Works for anything that can be accessed through an URL Works for any kind of media type with audio data Works well in most cases Simple to set up Negative Adds GnomeVFS dependency

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TOC

Contents: The Ruby-GNOME2 Project Multimedia Design User Interface Design Implementation Questions

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User Interface Design

Let’s write some code!

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TOC

Contents: The Ruby-GNOME2 Project Multimedia Design User Interface Design Implementation Questions

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Questions

Ask away!

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