An overview of GNOME platform libraries.
GNOME’s user interface libraries are used by all GNOME applications. They provide everything you need to create a beautiful and easy to use interface for your app.
GTK is GNOME’s user interface toolkit, and is a comprehensive resource for creating application user interfaces. It includes a wide range of user interface widgets, as well as providing access to an array of system-level features.
Libadwaita supplements GTK with additional widgets and classes. It is used to implement the standard GNOME design patterns as documented in the GNOME Human Interface Guidelines.
WebKitGTK allows adding web functionality to applications, such as HTML rendering and embedded web views.
Fonts & Rendering#
Simple text display and styling is provided by GTK. The GNOME platform also includes a set of lower-level font rendering and layout libraries, which apps may sometimes need to use directly for more specialised font and typographic functionality.
Fontconfig provides access to the fonts that are available on the system. It provides detailed information about available fonts, as well as the ability to match fonts according to criteria such as language coverage.
FreeType is a font rendering library used by the GNOME platform. Most applications are unlikely to need to use FreeType directly. However, it can be useful for specialist font and typographic features.
HarfBuzz is a text shaping library that is used by the GNOME platform. Most apps are unlikely to need to use HarfBuzz directly, unless they include font or typographic features.
Pango is a text layout library. It plays an important role in internationalization, has full Unicode support, and supports a range of writing systems. Pango APIs are exposed through GTK and can be used for things like setting text as bold or italic.
gdk-pixbuf is an image loading library which is used by GTK. For simple loading and display of images, GTK can typically used on its own. However, gdk-pixbuf does provide useful functionality for operating on images as pixel buffers, such as changing colors or creating composites from multiple images, and saving the result.
librsvg is a library that renders Scalable Vector Graphics (SVG). It can be used to display static SVG assets from GTK and gdk-pixbuf, or to render SVG documents to Cairo surfaces in general.
2D Drawing: Cairo#
Cairo can be used to draw custom 2D graphics. These can be embedded in GTK user interfaces, by drawing on GTK widgets. Graphics can also be outputted to PDF and SVG. Cairo graphics are resolution-independent and antialiased.
File System Access & Operations: GFile#
GIO provides a powerful virtual file system abstraction layer. Its GFile interface can be used to read information from the filesystem (such as traversing directories, querying file metadata, and so on) as well as and carrying out file operations. GFile can also be used to monitor files and directories for changes.
D-Bus is one of the primary IPC systems used in GNOME, and is used for communication between both applications and services. Applications can use D-Bus to communicate with system services, such as hardware-related daemons, or for communication between their own processes.
GDBus is included in the GIO library, and provides a comprehensive implementation of the D-Bus protocol, as well as high-level API to implement both providers and consumers of D-Bus interfaces.
GTK 4 includes its own built-in video playback capability, which can be used for simple video playback. For other multimedia requirements, GStreamer is an integrated part of the GNOME platform, and can be used for simple audio and video playback, through to complex non-linear multimedia editing.
GSettings is the GNOME library for reading and writing user settings. It allows storing a variety of settings types, including integers and arrays of strings.
The GNOME platform includes a variety of different data storage libraries, which are suitable for a range of requirements and needs.
GMarkup is an XML parser which can be used to read/write simple XML. It is appropriate for data which is read and written by the same app and not shared between programs.
Libxml2 is a highly compliant XML parser/generator. It is suited to reading and writing XML that is shared between different projects, and has a defined specification and XML schema. Example uses of libxml2 include document rendering and editing.
JSON-GLib implements a full JSON parser and generator using GLib and GObject, and integrates JSON with GLib data types.
libgda is a library which provides access to multiple SQL-based relational databases, including SQLite, MySQL, Postgres, MSAccess and more. Databases can either be local or remotely hosted. libgda includes a number of tools, including a SQL console, a data sources administration tool, and a database browser.
GOM is a data mapper for SQLite. It supports asynchronoous fetching and many-to-many tables, and helps with building search queries and database migrations.
GNOME libraries provide access to a range of networking functionality and features.
GIO includes high-level network features, such as monitoring the network state of the system, creating network connections, implementing network services, and accepting client connections.
GIO also provides a comprehensive set of low level networking APIs to abstract sockets, addresses, and proxies.
TLS & DNS support#
GIO provides support for TLS connections, both client and server side. It also supports resolvers for proxies, names and services.
Avahi implements Zeroconf Networking. It allows programs to discover services like printers on local networks without prior configuration. It also allows applications to set up services that are reachable through the local network without configuration; for example, a chat program that “finds” other chat users in a LAN without having to set up a central chat server first.
Soup is an HTTP library designed to be used in graphical applications. It uses asynchronous operations to avoid blocking the user interface while network requests are being made.
Soup provides functionality for using HTTP cookies, SSL encrypted connections, and the XML-RPC protocol based on HTTP.