Pango
Pango is a library for laying out and rendering text, with an emphasis on internationalization. It provides a powerful framework for handling complex text layout, including proper shaping for various writing systems, line breaking, and font selection.
Overview
Pango is designed to be a modular and flexible system, allowing developers to integrate it into various applications and toolkits. It is not a complete text editing solution but rather a low-level library that provides the fundamental capabilities for text handling. Pango supports a wide range of languages and scripts, including those that require complex shaping, such as Arabic, Hebrew, and Indic scripts.
Key Features
- Unicode Support: Pango is based on Unicode and handles a wide range of Unicode characters.
- Internationalization: Pango provides support for various writing systems, including left-to-right, right-to-left, and bidirectional text.
- Font Handling: Pango provides a flexible font selection mechanism that allows applications to choose the appropriate fonts for different scripts and languages. It typically relies on an underlying fontconfig library to manage font selection.
- Text Shaping: Pango handles complex text shaping requirements for scripts that require contextual glyph selection, such as Arabic and Indic scripts.
- Line Breaking: Pango provides line breaking algorithms that correctly handle the rules for different languages and scripts.
- Markup Support: Pango supports a subset of HTML-like markup that allows developers to specify attributes such as font styles, colors, and sizes within the text.
- Integration with Graphics Systems: Pango can be integrated with various graphics systems, allowing developers to render text on different platforms. This integration is often handled through backends that target specific graphics environments such as Cairo or DirectWrite.
Architecture
Pango is designed with a modular architecture. It consists of a core library that provides the basic text layout capabilities, along with various modules that provide support for different scripts, languages, and graphics systems. This modular design allows developers to customize Pango for their specific needs.
Usage
Pango is typically used by application developers who need to render text in a variety of languages and scripts. It can be used in conjunction with toolkits such as GTK and Qt, which provide higher-level widgets for text editing and display. Developers can also use Pango directly to render text in custom applications.
Relationship to other technologies
Pango often works in conjunction with other libraries. Fontconfig is frequently used for font selection. HarfBuzz is often employed for complex text shaping tasks. Cairo is commonly used as a rendering backend, providing a device-independent drawing API.
History
Pango was initially developed as part of the GNOME project and has become a widely used library for text layout and rendering in various applications and toolkits. It is an open-source project maintained by a community of developers.