FloatingPanelScaffold.kt

@ExperimentalAnimationApi
@Composable
@ExperimentalMaterialApi
fun FloatingPanelScaffold(
  modifier: Modifier = Modifier,
  scaffoldState: FloatingPanelScaffoldState = rememberFloatingPanelScaffoldState(),
  sidePanelState: SidePanelValue = SidePanelValue.Closed,
  isInListMode: Boolean = false,
  bottomPanelContent: @Composable ColumnScope.() -> Unit,
  bottomPanelModifier: Modifier = Modifier,
  bottomPanelShape: Shape = RoundedCornerShape(15.dp),
  bottomPanelElevation: Dp = BottomPanelScaffoldDefaults.SheetElevation,
  bottomPanelBackgroundColor: Color = MaterialTheme.colors.surface,
  bottomPanelContentColor: Color = contentColorFor(bottomPanelBackgroundColor),
  bottomPanelPeekHeight: Dp = BottomPanelScaffoldDefaults.SheetPeekHeight,
  bottomPanelGesturesEnabled: Boolean = true,
  sidePanelContent: @Composable ColumnScope.() -> Unit,
  sidePanelModifier: Modifier = Modifier,
  backgroundColor: Color = MaterialTheme.colors.background,
  contentColor: Color = contentColorFor(backgroundColor),
  content: @Composable (PaddingValues) -> Unit
) {
  BoxWithConstraints(modifier) {
    val coroutineScope = rememberCoroutineScope()
    val fullHeight = constraints.maxHeight.toFloat()
    val peekHeightPx = with(LocalDensity.current) { bottomPanelPeekHeight.toPx() }
    val bottomSheetHeight = remember { mutableStateOf(fullHeight) }

    LaunchedEffect(isInListMode) {
      coroutineScope.launch {
        if (isInListMode) {
          scaffoldState.bottomPanelState.expand()
        } else {
          scaffoldState.bottomPanelState.hide()
        }
      }
    }

    val swipeable = Modifier
      .then(
        if (!isInListMode)
          Modifier
            .nestedScroll(scaffoldState.bottomPanelState.nestedScrollConnection)
        else Modifier
      )
      .bottomPanelSwipeable(
        scaffoldState.bottomPanelState,
        fullHeight,
        peekHeightPx,
        bottomSheetHeight,
        if (isInListMode) false else bottomPanelGesturesEnabled
      )
      .onGloballyPositioned {
        bottomSheetHeight.value = it.size.height.toFloat()
      }

    FloatingPanelScaffoldStack(
      body = {
        Surface(
          color = backgroundColor,
          contentColor = contentColor
        ) {
          Column(Modifier.fillMaxSize()) {
            content(PaddingValues(bottom = bottomPanelPeekHeight))
          }
        }
      },
      bottomPanel = {
        Surface(
          swipeable
            .requiredHeightIn(min = bottomPanelPeekHeight)
            .then(bottomPanelModifier)
            .then(
              if (isInListMode) Modifier
                .padding(top = 16.dp, end = 2.dp) else Modifier
            ),
          shape = bottomPanelShape,
          elevation = bottomPanelElevation,
          color = bottomPanelBackgroundColor,
          contentColor = bottomPanelContentColor,
          content = { Column(content = bottomPanelContent) }
        )
      },
      sidePanel = {
        Surface(
          modifier = sidePanelModifier.then(
            if (isInListMode)
              Modifier
                .fillMaxHeight()
                .padding(top = 16.dp)
            else Modifier
          ),
          shape = RoundedCornerShape(topStart = 15.dp, bottomStart = 15.dp),
          elevation = bottomPanelElevation,
          color = bottomPanelBackgroundColor,
          contentColor = bottomPanelContentColor,
          content = {
            Column {
              AnimatedVisibility(
                visible = sidePanelState == SidePanelValue.Open,
                enter = fadeIn() + expandHorizontally(),
                exit = fadeOut() + shrinkHorizontally()
              ) {
                sidePanelContent()
              }
            }
          }
        )
      },
      isInListMode = isInListMode,
      bottomPanelOffset = scaffoldState.bottomPanelState.offset
    )
  }
}

@Composable
private fun FloatingPanelScaffoldStack(
  body: @Composable () -> Unit,
  bottomPanel: @Composable () -> Unit,
  sidePanel: @Composable () -> Unit,
  isInListMode: Boolean,
  bottomPanelOffset: State<Float>,
) {
  Layout(
    content = {
      body()
      sidePanel()
      bottomPanel()
    }
  ) { measurables, constraints ->
    val placeable = measurables.first().measure(constraints)
    layout(placeable.width, placeable.height) {
      placeable.placeRelative(0, 0)
      val sidePanelPlaceable = measurables[1].measure(constraints.copy(minWidth = 0, minHeight = 0))
      val sheetPlaceable = measurables[2].let {
        if (isInListMode) {
          it.measure(
            constraints.copy(
              maxWidth = constraints.maxWidth - sidePanelPlaceable.width,
              minHeight = 0
            )
          )
        } else {
          it.measure(constraints.copy(minWidth = 0, minHeight = 0))
        }
      }
      // Condition to draw first either sidePanel or bottomPanel in box
      if (isInListMode) {
        val sheetOffsetY = bottomPanelOffset.value.roundToInt()
        sheetPlaceable.placeRelative(0, sheetOffsetY)
        sidePanelPlaceable.placeRelative(
          constraints.maxWidth - sidePanelPlaceable.width,
          constraints.maxHeight / 2 - sidePanelPlaceable.height / 2
        )
      } else {
        sidePanelPlaceable.placeRelative(
          constraints.maxWidth - sidePanelPlaceable.width,
          constraints.maxHeight / 2 - sidePanelPlaceable.height / 2
        )
        val sheetOffsetY = bottomPanelOffset.value.roundToInt()
        sheetPlaceable.placeRelative(0, sheetOffsetY)
      }
    }
  }
}