Compose Modifier
approachLayout
Common
```kotlin
fun Modifier.approachLayout(
isMeasurementApproachInProgress: (lookaheadSize: IntSize) -> Boolean,
isPlacementApproachInProgress:
Placeable.PlacementScope.(lookaheadCoordinates: LayoutCoordinates) -> Boolean =
defaultPlacementApproachInProgress,
approachMeasure:
ApproachMeasureScope.(measurable: Measurable, constraints: Constraints) -> MeasureResult,
): Modifier
```
Creates an approach layout intended to help gradually approach the destination layout calculated
in the lookahead pass. This can be particularly helpful when the destination layout is
anticipated to change drastically and would consequently result in visual disruptions.
In order to create a smooth approach, an interpolation (often through animations) can be used in
`approachMeasure` to interpolate the measurement or placement from a previously recorded size
and/or position to the destination/target size and/or position. The destination size is available
in `ApproachMeasureScope` as `ApproachMeasureScope.lookaheadSize`. And the target position can
also be acquired in `ApproachMeasureScope` during placement by using
`LookaheadScope.localLookaheadPositionOf` with the layout's
`Placeable.PlacementScope.coordinates`. The sample code below illustrates how that can be
achieved.
`isMeasurementApproachInProgress` signals whether the measurement is in progress of approaching
destination size. It will be queried after the destination has been determined by the lookahead
pass, before `approachMeasure` is invoked. The lookahead size is provided to
`isMeasurementApproachInProgress` for convenience in deciding whether the destination size has
been reached.
`isMeasurementApproachInProgress` indicates whether the position is currently approaching
destination defined by the lookahead, hence it's a signal to the system for whether additional
approach placements are necessary. `isPlacementApproachInProgress` will be invoked after the
destination position has been determined by lookahead pass, and before the placement phase in
`approachMeasure`.
Once both `isMeasurementApproachInProgress` and `isPlacementApproachInProgress` return false, the
system may skip approach pass until additional approach passes are necessary as indicated by
`isMeasurementApproachInProgress` and `isPlacementApproachInProgress`.
**IMPORTANT**: It is important to be accurate in `isPlacementApproachInProgress` and
`isMeasurementApproachInProgress`. A prolonged indication of incomplete approach will prevent the
system from potentially skipping approach pass when possible.