Libinput: using libinput as a library

The libinput documentation includes a section on using libinput as a library, but with no prior experience with libinput, I found it inadequate to get me oriented. So, here are some additional notes.

Background

libinput is a library to handle input devices in Wayland compositors and to provide a generic X.Org input driver. It provides device detection, device handling, input device event processing and abstraction so minimize the amount of custom input code compositors need to provide the common set of functionality that users expect. Essentially, it is an interface to the input devices.

libinput is not used directly by Wayland applications, it is an input stack used by the compositor.

libinput is not used directly by X applications but rather through the custom xf86-input-libinput driver.  

Libinput may be used by programs other than these display servers. For example, the libinput distribution provides several tools for testing and interacting with libinput. Any program that accesses the input devices supported by libinput may use libinput to access them, as an alternative to accessing them directly.

libinput is designed to handle all input devices available on a system but it is possible to limit which devices libinput has access to. For example, the use of xf86-input-libinput depends on xorg.conf snippets for specific devices. But libinput works best if it handles all input devices as this allows for smarter handling of features that affect multiple devices.

libinput handles all common devices used to interact with a desktop system. This includes mice, keyboards, touchscreens, touchpads and graphics tablets. libinput does not expose the device type to the caller, it solely provides capabilities and the attached features (see this blog post).

libinput does not handle some devices. The primary reason is that these device have no clear interaction with a desktop environment.

See Building against libinput for guidance on configuration and linking the libinput library. 

Libinput does not have many configuration options. This is deliberate.

Initializing a context

The first step in using libinput is initializing a context. The context is manifest as a data structure. Most calls to libinput functions require this context as an argument.

The libinput API documentation has a section on Initialization and manipulation of libinput contexts.