Struct StepProgram 

pub struct StepProgram<M: Model> { /* private fields */ }

Host-driven, non-blocking program runner for WASM.

Wraps a Model and a WebBackend, providing a step-based execution model suitable for wasm32-unknown-unknown. No threads, no blocking, no std::time::Instant — all I/O and time are host-driven.

Lifecycle

1. StepProgram::new — create with model and initial terminal size.
2. StepProgram::init — call once to initialize the model and render the first frame.
3. StepProgram::step — call repeatedly from the host event loop (e.g., requestAnimationFrame).
4. Read outputs after each step via StepProgram::take_outputs.

Implementations

impl<M: Model> StepProgram<M>

pub fn new(model: M, width: u16, height: u16) -> Self

Create a new step program with the given model and initial terminal size.

pub fn with_backend(model: M, backend: WebBackend) -> Self

Create a step program with an existing WebBackend.

pub fn init(&mut self) -> Result<(), WebBackendError>

Initialize the model and render the first frame.

Must be called exactly once before step. Calls Model::init(), executes returned commands, and presents the initial frame.

pub fn step(&mut self) -> Result<StepResult, WebBackendError>

Process one batch of pending events, handle ticks, and render if dirty.

This is the main entry point for the host event loop. Call this after pushing events and advancing time.

Returns StepResult describing what happened during the step.

pub fn push_event(&mut self, event: Event)

Push a terminal event into the event queue.

Events are processed on the next step call.

pub fn advance_time(&mut self, dt: Duration)

Advance the deterministic clock by dt.

pub fn set_time(&mut self, now: Duration)

Set the deterministic clock to an absolute time.

pub fn resize(&mut self, width: u16, height: u16)

Resize the terminal.

Pushes a Resize event and updates the backend size. The resize is processed on the next step call.

pub fn take_outputs(&mut self) -> WebOutputs

Take the captured outputs (rendered buffer, logs), leaving empty defaults.

pub fn outputs(&self) -> &WebOutputs

Read the captured outputs without consuming them.

pub fn model(&self) -> &M

Access the model.

pub fn model_mut(&mut self) -> &mut M

Mutably access the model.

pub fn backend(&self) -> &WebBackend

Access the backend.

pub fn backend_mut(&mut self) -> &mut WebBackend

Mutably access the backend.

pub fn is_running(&self) -> bool

Whether the program is still running.

pub fn is_initialized(&self) -> bool

Whether the program has been initialized.

pub fn frame_idx(&self) -> u64

Current frame index.

pub fn size(&self) -> (u16, u16)

Current terminal dimensions.

pub fn tick_rate(&self) -> Option<Duration>

Current tick rate, if any.

pub fn pool(&self) -> &GraphemePool

Access the grapheme pool (needed for deterministic checksumming).