spiegel-keyman/common/engine/keyboardprocessor/doc/markdown_files/index.md

Keyman Keyboard Processor API

Requirements

1. Cross platform.
2. Cross language.
3. Facilitate stateless operation of the Engine.
4. Keyboard format agnostic -- support both KMN and future LDML based keyboards.
5. Support querying Engine attributes.
6. Support querying Keyboard attributes.
7. Idempotent

Design decisions in support of requirements:

• Use C or C99 types and calling convention for the interface, it has the broadest language FFI support. [1,2]
• Have client (platform glue) code load keyboards, manage & pass state. [3,4,7]
• Provide query calls to return static attributes data for keyboards and engine [5,6]
• Provide get/set calls for client accessible keyboard state information [3,4]

Glossary

• Platform layer: the code that consumes the Keyman Keyboard Processor API, and provides the operating system-specific handling of keystroke events and integration with applications.
• Client Application: the application that has the focus and receives text events from the Platform layer.
• Context: Text preceding the insertion point
• Marker: Positional state that can be placed in the Context.
• Keyboard: A set of rules for execution my an Engine
• Option: A variable in a dynamic or static key value store.
• Processor: The component that implements this API and can parse and execute a particular keyboard.
• State: An object that hold internal state of the Processor for a given insertion point
• Action: A directive output by the processor detailing how the Platform layer should transform the Client Application's text buffer. There may be several items produced by a single keyboard event.
• Keyboard Event: A virtual key board event and modifier map recevied from the platform to be processed with the state object for this Client application.

API

Namespace

All calls, types and enums are prefixed with the namespace identifier km_kbp_