A Chat object provides a generic UI to read a series of Posts in a Dialogue stored in the pddb - and to Author a new Post.
The idea is to provide a solid common Xous Chat interface, so that Chat Apps can specialize in the unique aspects of a chat Platform protocol (Matrix, Signal etc).
A Chat App will typically call Chat::new() and then Chat::dialogue_set() with a pddb dict and key holding a Dialogue of Posts. The Chat object will fire-up the UI and retrieve the Dialogue from the pddb. The user will be able to peruse the stored Posts in the Dialogue - and potentially Author a new Post. A new User Post will be sent to the Chat App in a MemoryMessage via the (optional) CID and Opcode provided by the Chat App. Conversely, when the Chat App receives a new Post from the Platform, it will call Chat::post_add() to have it saved in the pddb.
The Chat UI will also accept (optional) opcodes to forward raw-keystrokes and UI-Events to the Chat App. This allows the Chat App to respond to key UI Events. For example if the User navigates to the top of the list of stored Posts, then the Chat App might retrieve older Posts from the Platform to be stored Dialogue with calls to Chat::post_add().