3.2. Transport — pluggable lambda-based IPC for imgui commands

Lambda-typed transport for dasImgui live commands. Transport is a closure (action, payload) → JsonValue?; live_api_transport(url) returns a transport that POSTs {"name": action, "args": payload} to <url>/command and parses the JSON response. Users substitute mocks, in-process buses, or alternative transports without changing call sites.

Wait helpers — await_imgui, await_imgui_frame, send_with_await — drive client-side polling against the host’s imgui_await endpoint. Server-side blocking is incompatible with the GLFW-main-thread invariant (the dispatch handler runs on the same thread that advances frames), so waits are always client-side; send_with_await dispatches on await_frames / await_until: "quiescent" / fire_and_forget and default-polls quiescence otherwise.

3.2.1. Type aliases

Transport = lambda<(action:string const;var payload:JsonValue? ):JsonValue?>

typedef Transport = lambda<(action:string const;var payload:json::JsonValue? -const):json::JsonValue?> aka Transport

3.2.2. Constants

DEFAULT_AWAIT_POLL_MS = 0x32

DEFAULT_AWAIT_POLL_MS:uint const

DEFAULT_AWAIT_TIMEOUT_SEC = 5f

DEFAULT_AWAIT_TIMEOUT_SEC:float const

DEFAULT_REQUEST_TIMEOUT_SEC = 10

DEFAULT_REQUEST_TIMEOUT_SEC:int const

3.2.3. Structures

HttpReply
Fields:

  • status : int - < HTTP status code; 0 when there was no response (connect refused or request timed out).

  • body : string - < Response body, or “” on no response.

3.2.4. Transport construction

live_api_transport(url: string ): Transport

Default transport: POSTs {"name": action, "args": payload} to <url>/command and parses the JSON response. url is captured by value, so the returned lambda is safe to reuse. Uses http_post’s per-request timeout, so a wedged host yields null rather than blocking the body.

Arguments:

  • url : string

3.2.5. Send / receive

receive_imgui_snapshot(transport: Transport ): JsonValue?

Convenience for send_imgui_command(transport, "imgui_snapshot", null) — fetches the full widget snapshot.

Arguments:
send_imgui_command(transport: Transport; action: string; payload: JsonValue? ): JsonValue?

Send one command through transport and return the parsed JSON response.

Arguments:

3.2.6. Awaiting

await_imgui(transport: Transport; until: string = "quiescent"; timeout_sec: float = DEFAULT_AWAIT_TIMEOUT_SEC ): bool

Poll imgui_await until value.quiescent flips true; returns true on quiescence, false on timeout.

Arguments:

  • transport : Transport

  • until : string

  • timeout_sec : float

await_imgui_frame(transport: Transport; target_frame: int; timeout_sec: float = DEFAULT_AWAIT_TIMEOUT_SEC ): bool

Poll imgui_await until server-side value.frame >= target_frame; reuses the frame: arg so server flips quiescent at the right tick.

Arguments:

  • transport : Transport

  • target_frame : int

  • timeout_sec : float

send_with_await(transport: Transport; action: string; payload: JsonValue?; timeout_sec: float = DEFAULT_AWAIT_TIMEOUT_SEC ): JsonValue?

Send action/payload and honor any await_* modifier the server merged into the response. Dispatches on await_frames / await_until: "quiescent" / fire_and_forget; otherwise default-polls quiescence with timeout_sec.

Arguments:

3.2.7. Raw HTTP

http_get(url: string; timeout_sec: int = DEFAULT_REQUEST_TIMEOUT_SEC ): HttpReply

GET url with a hard per-request timeout. status == 0 means no response (refused / timed out).

Arguments:

  • url : string

  • timeout_sec : int

http_post(url: string; body: string; timeout_sec: int = DEFAULT_REQUEST_TIMEOUT_SEC ): HttpReply

POST body as application/json to url with a hard per-request timeout.

Arguments:

  • url : string

  • body : string

  • timeout_sec : int