MeasureRow

const · packages/primitives/src/state/virtual.ts:402

const MeasureRow: Mount.MountDefinitionWithArgs<
  'MeasureRow',
  { key: Schema.String },
  {
    readonly _tag: 'RowMeasured'
    readonly key: string
    readonly height: number
  }
>

One row's height, reported on every resize starting with the current one. The key is the application's row identity, echoed back so the parent files the height without tracking which Mount sent what.