GObjectIntrospection

GObject Introspection is a middleware and data format used by GNOME libraries to expose APIs written in C that use the GObject type system to dynamic programming languages. Its primary aim is to enable language bindings to access a library’s functionality without requiring hand-written wrappers for every API, by providing a consistent, language-agnostic description of the library’s objects, types, functions, signals, properties, and constants.

The system relies on two related data forms. A human-readable GIR (GObject-Introspection Repository) file, generated during development by a scanner tool such as g-ir-scanner, describes the library’s API in XML. This can be supplemented with annotations to convey additional information. The GIR is then compiled into a binary typelib (.typelib) used at runtime by language bindings. At runtime, the GIRepository API loads the appropriate typelib and exposes the library’s API to the host language.

Languages and bindings around GObject Introspection include Python (via PyGObject), JavaScript (via GJS), and other languages that can interoperate with the GI framework. Popular GNOME libraries such as GTK and GStreamer expose their APIs through introspection, enabling multi-language development with a single source of API metadata.

GObject Introspection has become a core part of GNOME’s cross-language ecosystem, simplifying the creation of language bindings and enabling dynamic binding generation, improved API consistency, and easier maintenance across multiple languages and platforms.