pub type ToolPollFn = extern "C" fn(handle: StepHandle, partial_cb: Option<ToolPartialCb>, user_data: *mut c_void) -> StepResult;Expand description
poll(handle, partial_cb, user_data) -> StepResult. Non-blocking. Must
observe the cancel flag (set by ToolCancelFn) and return Done/Err
within a bounded number of polls. Borrows handle (does not free it).