# llimphi-wasm-app-sdk

The guest side of Tier 3 WASM apps.

An app implements `WasmApp`: its own `Model`, an `update(&mut self, Msg)`
transition and a `view(&self, &mut Ui) -> WireNode`. The UI is built with
`llimphi_wire_view`'s free constructors (`col`/`row`/`text`) for the
non-interactive parts and with the `Ui` for the interactive ones
(`button`/`text_input`/`checkbox`).

**Events with payload.** The `Ui` assigns an `EventId` to each control and stores
its handler. The node carries only the id; on firing, the host sends
`dispatch(event_id, payload)`. The guest looks in its table and rebuilds the
`Msg`: a button yields its fixed `Msg`, an input yields `f(typed_text)`, a
checkbox `f(new_state)`. That is why **`Msg` no longer crosses the boundary** —
only the id and the `EventPayload` — so `Msg` is freed from (de)serializing:
`Clone` is enough.

`export_wasm_app!` generates the ABI: `wasm_init`, `wasm_view() -> u64`
(ptr<<32|len of the postcard `WireNode`), `wasm_dispatch(event_id, ptr, len)`,
`wasm_alloc`, `wasm_free`. The `Model` and the handler table live in the guest.

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Part of **llimphi** — see [llimphi](../README.md).