react-native-mask-segment-canvas/docs/docs/api/callbacks.md

id	title
callbacks	Props: Callbacks

📞 Props: Callbacks

Prop	Signature	Description
onWatch	(state, durationMs, detail?) => void	Initialization stage callback; durationMs is relative to this init start
onPaintCallback	(payload: PaintCallbackPayload) => void	Fires on successful paint, or when tapping a region without a brush selected
onError	(message, error?) => void	Segmentation or loading failure

PaintCallbackPayload

(Discriminated union, distinguished by payload.kind):

// Successful paint
{
  kind: 'painted';
  regionId: number;
  regionName: string;
  color: BgrColor;
  configJson?: Record<string, unknown>; // from setPaintColor / initialPaintConfigJson
}

// Tapped a valid region without selecting a brush (no paint performed)
{
  kind: 'brush_required';
  hint: string;       // e.g. "Please select a brush color first (bottom color bar or ref.setPaintColor)"
  regionId: number;
  regionName: string;
}

Example:

onPaintCallback={payload => {
  if (payload.kind === 'brush_required') {
    showToast(payload.hint);
    return;
  }
  savePaintRecord(payload.regionId, payload.color, payload.configJson);
}}

onWatch detail (MaskSegmentWatchDetail)

Field	Type	Description
regionCount	number	Current effective region count
maskPathsReady	boolean	Whether outline Skia paths are ready
freqLayersReady	boolean	Whether frequency Shader textures are ready
errorMessage	string	Failure description in error state

onWatch State Flow

init
  → images_loaded      Origin + mask read complete
  → mask_aligned       Mask dimensions aligned
  → mask_sampled       Mask pixel sampling complete
  → regions_ready      Region extraction succeeded
  → layers_ready       Paint texture layers ready (detail.maskPathsReady may still be false)
  → interactive        Interactive (can tap regions, select colors, paint)
  → mask_paths_ready   Outline paths ready (carousel dashed outlines can display; detail.maskPathsReady is true)
  → error              Failure (detail.errorMessage has description)

layers_ready / interactive may fire before outline paths finish computing. If the host dismisses a blocking loader at interactive, the user can already operate; carousel dashed outlines appear automatically after mask_paths_ready.