Capture session lifecycle

Both FaceCaptureSession and FingerprintCaptureSession are EventEmitters with the same overall shape:


idle → initializing → ready → detecting → hold_steady → capturing → (quality_check) → completed
                                                                                     ↘ retry → detecting
                                                                                     ↘ error

You call start(). The session opens the camera, runs detection, emits a 'guidance' event on every frame, fires 'captured' when a frame passes the gates, then 'completed'. Call stop() to tear down early.

Events

Event	Fired by	Payload
`started`	both	none
`state_change`	both	`FaceCaptureState` \| fingerprint state
`detection`	both	`FaceDetectionEvent` \| `HandDetectionEvent`
`guidance`	both	`GuidanceState`
`face_quality`	face	`FaceQualityResult`
`quality`	fingerprint	`QualityInfo`
`quality_failed`	fingerprint	`QualityInfo`
`antispoof`	face	`{ score, passed }`
`captured`	both	per-modality result
`step_change`	fingerprint	`{ index, step }`
`completed`	both	final result
`error`	both	`SladeIDError` subclass
`stopped`	both	none

Reading the state

Wire 'guidance' to the UI for prompts (“hold steady”, “move closer”). Wire 'state_change' for higher-level UI changes (showing a countdown, swapping the overlay). Wire 'captured' and 'completed' for the success path; wire 'error' for the failure path.

Used in

Every capture guide.
Capture sessions reference.