Move Bouncer UI into a separate compose function

Bug: 310005730
Test: everything builds
Test: manually, verified that bouncer UI renders as expected
Flag: ACONFIG com.android.systemui.scene_container DEVELOPMENT
Change-Id: I5b724b0d705b9d51692e0d1392258cd892d36716
diff --git a/packages/SystemUI/compose/facade/enabled/src/com/android/systemui/scene/BouncerSceneModule.kt b/packages/SystemUI/compose/facade/enabled/src/com/android/systemui/scene/BouncerSceneModule.kt
index ddc3d3a..1860c9f 100644
--- a/packages/SystemUI/compose/facade/enabled/src/com/android/systemui/scene/BouncerSceneModule.kt
+++ b/packages/SystemUI/compose/facade/enabled/src/com/android/systemui/scene/BouncerSceneModule.kt
@@ -18,8 +18,8 @@
 
 import android.app.AlertDialog
 import android.content.Context
+import com.android.systemui.bouncer.ui.composable.BouncerDialogFactory
 import com.android.systemui.bouncer.ui.composable.BouncerScene
-import com.android.systemui.bouncer.ui.composable.BouncerSceneDialogFactory
 import com.android.systemui.dagger.SysUISingleton
 import com.android.systemui.dagger.qualifiers.Application
 import com.android.systemui.scene.shared.model.Scene
@@ -38,8 +38,8 @@
 
         @Provides
         @SysUISingleton
-        fun bouncerSceneDialogFactory(@Application context: Context): BouncerSceneDialogFactory {
-            return object : BouncerSceneDialogFactory {
+        fun bouncerSceneDialogFactory(@Application context: Context): BouncerDialogFactory {
+            return object : BouncerDialogFactory {
                 override fun invoke(): AlertDialog {
                     return SystemUIDialog(context)
                 }
diff --git a/packages/SystemUI/compose/features/src/com/android/systemui/bouncer/ui/composable/BouncerContent.kt b/packages/SystemUI/compose/features/src/com/android/systemui/bouncer/ui/composable/BouncerContent.kt
new file mode 100644
index 0000000..ba80a8d
--- /dev/null
+++ b/packages/SystemUI/compose/features/src/com/android/systemui/bouncer/ui/composable/BouncerContent.kt
@@ -0,0 +1,734 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.systemui.bouncer.ui.composable
+
+import android.app.AlertDialog
+import android.app.Dialog
+import android.content.DialogInterface
+import androidx.compose.animation.Crossfade
+import androidx.compose.animation.core.animateFloatAsState
+import androidx.compose.animation.core.snap
+import androidx.compose.animation.core.tween
+import androidx.compose.foundation.ExperimentalFoundationApi
+import androidx.compose.foundation.Image
+import androidx.compose.foundation.combinedClickable
+import androidx.compose.foundation.gestures.detectTapGestures
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.aspectRatio
+import androidx.compose.foundation.layout.fillMaxHeight
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.heightIn
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.layout.widthIn
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.KeyboardArrowDown
+import androidx.compose.material3.Button
+import androidx.compose.material3.ButtonDefaults
+import androidx.compose.material3.DropdownMenu
+import androidx.compose.material3.DropdownMenuItem
+import androidx.compose.material3.Icon
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.asImageBitmap
+import androidx.compose.ui.graphics.graphicsLayer
+import androidx.compose.ui.input.pointer.pointerInput
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.platform.LocalLayoutDirection
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.DpOffset
+import androidx.compose.ui.unit.LayoutDirection
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.times
+import com.android.compose.PlatformButton
+import com.android.compose.animation.scene.ElementKey
+import com.android.compose.animation.scene.SceneKey
+import com.android.compose.animation.scene.SceneScope
+import com.android.compose.animation.scene.SceneTransitionLayout
+import com.android.compose.animation.scene.transitions
+import com.android.compose.modifiers.thenIf
+import com.android.systemui.bouncer.shared.model.BouncerActionButtonModel
+import com.android.systemui.bouncer.ui.helper.BouncerSceneLayout
+import com.android.systemui.bouncer.ui.viewmodel.AuthMethodBouncerViewModel
+import com.android.systemui.bouncer.ui.viewmodel.BouncerViewModel
+import com.android.systemui.bouncer.ui.viewmodel.PasswordBouncerViewModel
+import com.android.systemui.bouncer.ui.viewmodel.PatternBouncerViewModel
+import com.android.systemui.bouncer.ui.viewmodel.PinBouncerViewModel
+import com.android.systemui.common.shared.model.Text.Companion.loadText
+import com.android.systemui.common.ui.compose.Icon
+import com.android.systemui.fold.ui.composable.foldPosture
+import com.android.systemui.fold.ui.helper.FoldPosture
+import com.android.systemui.res.R
+import kotlin.math.abs
+import kotlin.math.max
+import kotlin.math.pow
+
+@Composable
+fun BouncerContent(
+    viewModel: BouncerViewModel,
+    dialogFactory: BouncerDialogFactory,
+    modifier: Modifier
+) {
+    val isFullScreenUserSwitcherEnabled = viewModel.isUserSwitcherVisible
+    val isSideBySideSupported by viewModel.isSideBySideSupported.collectAsState()
+    val layout = calculateLayout(isSideBySideSupported = isSideBySideSupported)
+
+    when (layout) {
+        BouncerSceneLayout.STANDARD ->
+            StandardLayout(
+                viewModel = viewModel,
+                dialogFactory = dialogFactory,
+                modifier = modifier,
+            )
+        BouncerSceneLayout.SIDE_BY_SIDE ->
+            SideBySideLayout(
+                viewModel = viewModel,
+                dialogFactory = dialogFactory,
+                isUserSwitcherVisible = isFullScreenUserSwitcherEnabled,
+                modifier = modifier,
+            )
+        BouncerSceneLayout.STACKED ->
+            StackedLayout(
+                viewModel = viewModel,
+                dialogFactory = dialogFactory,
+                isUserSwitcherVisible = isFullScreenUserSwitcherEnabled,
+                modifier = modifier,
+            )
+        BouncerSceneLayout.SPLIT ->
+            SplitLayout(
+                viewModel = viewModel,
+                dialogFactory = dialogFactory,
+                modifier = modifier,
+            )
+    }
+}
+
+/**
+ * Renders the contents of the actual bouncer UI, the area that takes user input to do an
+ * authentication attempt, including all messaging UI (directives, reasoning, errors, etc.).
+ */
+@Composable
+private fun StandardLayout(
+    viewModel: BouncerViewModel,
+    dialogFactory: BouncerDialogFactory,
+    modifier: Modifier = Modifier,
+    outputOnly: Boolean = false,
+) {
+    val foldPosture: FoldPosture by foldPosture()
+    val isSplitAroundTheFoldRequired by viewModel.isFoldSplitRequired.collectAsState()
+    val isSplitAroundTheFold =
+        foldPosture == FoldPosture.Tabletop && !outputOnly && isSplitAroundTheFoldRequired
+    val currentSceneKey =
+        if (isSplitAroundTheFold) SceneKeys.SplitSceneKey else SceneKeys.ContiguousSceneKey
+
+    SceneTransitionLayout(
+        currentScene = currentSceneKey,
+        onChangeScene = {},
+        transitions = SceneTransitions,
+        modifier = modifier,
+    ) {
+        scene(SceneKeys.ContiguousSceneKey) {
+            FoldSplittable(
+                viewModel = viewModel,
+                dialogFactory = dialogFactory,
+                outputOnly = outputOnly,
+                isSplit = false,
+            )
+        }
+
+        scene(SceneKeys.SplitSceneKey) {
+            FoldSplittable(
+                viewModel = viewModel,
+                dialogFactory = dialogFactory,
+                outputOnly = outputOnly,
+                isSplit = true,
+            )
+        }
+    }
+}
+
+/**
+ * Renders the "standard" layout of the bouncer, where the bouncer is rendered on its own (no user
+ * switcher UI) and laid out vertically, centered horizontally.
+ *
+ * If [isSplit] is `true`, the top and bottom parts of the bouncer are split such that they don't
+ * render across the location of the fold hardware when the device is fully or part-way unfolded
+ * with the fold hinge in a horizontal position.
+ *
+ * If [outputOnly] is `true`, only the "output" part of the UI is shown (where the entered PIN
+ * "shapes" appear), if `false`, the entire UI is shown, including the area where the user can enter
+ * their PIN or pattern.
+ */
+@Composable
+private fun SceneScope.FoldSplittable(
+    viewModel: BouncerViewModel,
+    dialogFactory: BouncerDialogFactory,
+    outputOnly: Boolean,
+    isSplit: Boolean,
+    modifier: Modifier = Modifier,
+) {
+    val message: BouncerViewModel.MessageViewModel by viewModel.message.collectAsState()
+    val dialogMessage: String? by viewModel.throttlingDialogMessage.collectAsState()
+    var dialog: Dialog? by remember { mutableStateOf(null) }
+    val actionButton: BouncerActionButtonModel? by viewModel.actionButton.collectAsState()
+    val splitRatio =
+        LocalContext.current.resources.getFloat(
+            R.dimen.motion_layout_half_fold_bouncer_height_ratio
+        )
+
+    Column(modifier = modifier.padding(horizontal = 32.dp)) {
+        // Content above the fold, when split on a foldable device in a "table top" posture:
+        Box(
+            modifier =
+                Modifier.element(SceneElements.AboveFold).fillMaxWidth().thenIf(isSplit) {
+                    Modifier.weight(splitRatio)
+                },
+        ) {
+            Column(
+                horizontalAlignment = Alignment.CenterHorizontally,
+                modifier = Modifier.fillMaxWidth().padding(top = 92.dp),
+            ) {
+                Crossfade(
+                    targetState = message,
+                    label = "Bouncer message",
+                    animationSpec = if (message.isUpdateAnimated) tween() else snap(),
+                ) { message ->
+                    Text(
+                        text = message.text,
+                        color = MaterialTheme.colorScheme.onSurface,
+                        style = MaterialTheme.typography.bodyLarge,
+                    )
+                }
+
+                Spacer(Modifier.heightIn(min = 21.dp, max = 48.dp))
+
+                UserInputArea(
+                    viewModel = viewModel,
+                    visibility = UserInputAreaVisibility.OUTPUT_ONLY,
+                )
+            }
+        }
+
+        // Content below the fold, when split on a foldable device in a "table top" posture:
+        Box(
+            modifier =
+                Modifier.element(SceneElements.BelowFold).fillMaxWidth().thenIf(isSplit) {
+                    Modifier.weight(1 - splitRatio)
+                },
+        ) {
+            Column(
+                horizontalAlignment = Alignment.CenterHorizontally,
+                modifier = Modifier.fillMaxWidth(),
+            ) {
+                if (!outputOnly) {
+                    Box(Modifier.weight(1f)) {
+                        UserInputArea(
+                            viewModel = viewModel,
+                            visibility = UserInputAreaVisibility.INPUT_ONLY,
+                            modifier = Modifier.align(Alignment.Center),
+                        )
+                    }
+                }
+
+                Spacer(Modifier.heightIn(min = 21.dp, max = 48.dp))
+
+                val actionButtonModifier = Modifier.height(56.dp)
+
+                actionButton.let { actionButtonViewModel ->
+                    if (actionButtonViewModel != null) {
+                        BouncerActionButton(
+                            viewModel = actionButtonViewModel,
+                            modifier = actionButtonModifier,
+                        )
+                    } else {
+                        Spacer(modifier = actionButtonModifier)
+                    }
+                }
+
+                Spacer(Modifier.height(48.dp))
+            }
+        }
+
+        if (dialogMessage != null) {
+            if (dialog == null) {
+                dialog =
+                    dialogFactory().apply {
+                        setMessage(dialogMessage)
+                        setButton(
+                            DialogInterface.BUTTON_NEUTRAL,
+                            context.getString(R.string.ok),
+                        ) { _, _ ->
+                            viewModel.onThrottlingDialogDismissed()
+                        }
+                        setCancelable(false)
+                        setCanceledOnTouchOutside(false)
+                        show()
+                    }
+            }
+        } else {
+            dialog?.dismiss()
+            dialog = null
+        }
+    }
+}
+
+/**
+ * Renders the user input area, where the user interacts with the UI to enter their credentials.
+ *
+ * For example, this can be the pattern input area, the password text box, or pin pad.
+ */
+@Composable
+private fun UserInputArea(
+    viewModel: BouncerViewModel,
+    visibility: UserInputAreaVisibility,
+    modifier: Modifier = Modifier,
+) {
+    val authMethodViewModel: AuthMethodBouncerViewModel? by
+        viewModel.authMethodViewModel.collectAsState()
+
+    when (val nonNullViewModel = authMethodViewModel) {
+        is PinBouncerViewModel ->
+            when (visibility) {
+                UserInputAreaVisibility.OUTPUT_ONLY ->
+                    PinInputDisplay(
+                        viewModel = nonNullViewModel,
+                        modifier = modifier,
+                    )
+                UserInputAreaVisibility.INPUT_ONLY ->
+                    PinPad(
+                        viewModel = nonNullViewModel,
+                        modifier = modifier,
+                    )
+            }
+        is PasswordBouncerViewModel ->
+            if (visibility == UserInputAreaVisibility.INPUT_ONLY) {
+                PasswordBouncer(
+                    viewModel = nonNullViewModel,
+                    modifier = modifier,
+                )
+            }
+        is PatternBouncerViewModel ->
+            if (visibility == UserInputAreaVisibility.INPUT_ONLY) {
+                PatternBouncer(
+                    viewModel = nonNullViewModel,
+                    modifier = modifier.aspectRatio(1f, matchHeightConstraintsFirst = false)
+                )
+            }
+        else -> Unit
+    }
+}
+
+/**
+ * Renders the action button on the bouncer, which triggers either Return to Call or Emergency Call.
+ */
+@OptIn(ExperimentalFoundationApi::class)
+@Composable
+private fun BouncerActionButton(
+    viewModel: BouncerActionButtonModel,
+    modifier: Modifier = Modifier,
+) {
+    Button(
+        onClick = viewModel.onClick,
+        modifier =
+            modifier.thenIf(viewModel.onLongClick != null) {
+                Modifier.combinedClickable(
+                    onClick = viewModel.onClick,
+                    onLongClick = viewModel.onLongClick,
+                )
+            },
+        colors =
+            ButtonDefaults.buttonColors(
+                containerColor = MaterialTheme.colorScheme.tertiaryContainer,
+                contentColor = MaterialTheme.colorScheme.onTertiaryContainer,
+            ),
+    ) {
+        Text(
+            text = viewModel.label,
+            style = MaterialTheme.typography.bodyMedium,
+        )
+    }
+}
+
+/** Renders the UI of the user switcher that's displayed on large screens next to the bouncer UI. */
+@Composable
+private fun UserSwitcher(
+    viewModel: BouncerViewModel,
+    modifier: Modifier = Modifier,
+) {
+    val selectedUserImage by viewModel.selectedUserImage.collectAsState(null)
+    val dropdownItems by viewModel.userSwitcherDropdown.collectAsState(emptyList())
+
+    Column(
+        horizontalAlignment = Alignment.CenterHorizontally,
+        verticalArrangement = Arrangement.Center,
+        modifier = modifier,
+    ) {
+        selectedUserImage?.let {
+            Image(
+                bitmap = it.asImageBitmap(),
+                contentDescription = null,
+                modifier = Modifier.size(SelectedUserImageSize),
+            )
+        }
+
+        val (isDropdownExpanded, setDropdownExpanded) = remember { mutableStateOf(false) }
+
+        dropdownItems.firstOrNull()?.let { firstDropdownItem ->
+            Spacer(modifier = Modifier.height(40.dp))
+
+            Box {
+                PlatformButton(
+                    modifier =
+                        Modifier
+                            // Remove the built-in padding applied inside PlatformButton:
+                            .padding(vertical = 0.dp)
+                            .width(UserSwitcherDropdownWidth)
+                            .height(UserSwitcherDropdownHeight),
+                    colors =
+                        ButtonDefaults.buttonColors(
+                            containerColor = MaterialTheme.colorScheme.surfaceContainerHighest,
+                            contentColor = MaterialTheme.colorScheme.onSurface,
+                        ),
+                    onClick = { setDropdownExpanded(!isDropdownExpanded) },
+                ) {
+                    val context = LocalContext.current
+                    Text(
+                        text = checkNotNull(firstDropdownItem.text.loadText(context)),
+                        style = MaterialTheme.typography.headlineSmall,
+                        maxLines = 1,
+                        overflow = TextOverflow.Ellipsis,
+                    )
+
+                    Spacer(modifier = Modifier.weight(1f))
+
+                    Icon(
+                        imageVector = Icons.Default.KeyboardArrowDown,
+                        contentDescription = null,
+                        modifier = Modifier.size(32.dp),
+                    )
+                }
+
+                UserSwitcherDropdownMenu(
+                    isExpanded = isDropdownExpanded,
+                    items = dropdownItems,
+                    onDismissed = { setDropdownExpanded(false) },
+                )
+            }
+        }
+    }
+}
+
+/**
+ * Renders the dropdown menu that displays the actual users and/or user actions that can be
+ * selected.
+ */
+@Composable
+private fun UserSwitcherDropdownMenu(
+    isExpanded: Boolean,
+    items: List<BouncerViewModel.UserSwitcherDropdownItemViewModel>,
+    onDismissed: () -> Unit,
+) {
+    val context = LocalContext.current
+
+    // TODO(b/303071855): once the FR is fixed, remove this composition local override.
+    MaterialTheme(
+        colorScheme =
+            MaterialTheme.colorScheme.copy(
+                surface = MaterialTheme.colorScheme.surfaceContainerHighest,
+            ),
+        shapes = MaterialTheme.shapes.copy(extraSmall = RoundedCornerShape(28.dp)),
+    ) {
+        DropdownMenu(
+            expanded = isExpanded,
+            onDismissRequest = onDismissed,
+            offset =
+                DpOffset(
+                    x = 0.dp,
+                    y = -UserSwitcherDropdownHeight,
+                ),
+            modifier = Modifier.width(UserSwitcherDropdownWidth),
+        ) {
+            items.forEach { userSwitcherDropdownItem ->
+                DropdownMenuItem(
+                    leadingIcon = {
+                        Icon(
+                            icon = userSwitcherDropdownItem.icon,
+                            tint = MaterialTheme.colorScheme.primary,
+                            modifier = Modifier.size(28.dp),
+                        )
+                    },
+                    text = {
+                        Text(
+                            text = checkNotNull(userSwitcherDropdownItem.text.loadText(context)),
+                            style = MaterialTheme.typography.bodyLarge,
+                            color = MaterialTheme.colorScheme.onSurface,
+                        )
+                    },
+                    onClick = {
+                        onDismissed()
+                        userSwitcherDropdownItem.onClick()
+                    },
+                )
+            }
+        }
+    }
+}
+
+/**
+ * Renders the bouncer UI in split mode, with half on one side and half on the other side, swappable
+ * by double-tapping on the side.
+ */
+@Composable
+private fun SplitLayout(
+    viewModel: BouncerViewModel,
+    dialogFactory: BouncerDialogFactory,
+    modifier: Modifier = Modifier,
+) {
+    SwappableLayout(
+        startContent = { startContentModifier ->
+            StandardLayout(
+                viewModel = viewModel,
+                dialogFactory = dialogFactory,
+                outputOnly = true,
+                modifier = startContentModifier,
+            )
+        },
+        endContent = { endContentModifier ->
+            UserInputArea(
+                viewModel = viewModel,
+                visibility = UserInputAreaVisibility.INPUT_ONLY,
+                modifier = endContentModifier,
+            )
+        },
+        modifier = modifier
+    )
+}
+
+/**
+ * Arranges the given two contents side-by-side, supporting a double tap anywhere on the background
+ * to flip their positions.
+ */
+@Composable
+private fun SwappableLayout(
+    startContent: @Composable (Modifier) -> Unit,
+    endContent: @Composable (Modifier) -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    val layoutDirection = LocalLayoutDirection.current
+    val isLeftToRight = layoutDirection == LayoutDirection.Ltr
+    val (isSwapped, setSwapped) = rememberSaveable(isLeftToRight) { mutableStateOf(!isLeftToRight) }
+
+    Row(
+        modifier =
+            modifier.pointerInput(Unit) {
+                detectTapGestures(
+                    onDoubleTap = { offset ->
+                        // Depending on where the user double tapped, switch the elements such that
+                        // the endContent is closer to the side that was double tapped.
+                        setSwapped(offset.x < size.width / 2)
+                    }
+                )
+            },
+    ) {
+        val animatedOffset by
+            animateFloatAsState(
+                targetValue =
+                    if (!isSwapped) {
+                        // When startContent is first, both elements have their natural placement so
+                        // they are not offset in any way.
+                        0f
+                    } else if (isLeftToRight) {
+                        // Since startContent is not first, the elements have to be swapped
+                        // horizontally. In the case of LTR locales, this means pushing startContent
+                        // to the right, hence the positive number.
+                        1f
+                    } else {
+                        // Since startContent is not first, the elements have to be swapped
+                        // horizontally. In the case of RTL locales, this means pushing startContent
+                        // to the left, hence the negative number.
+                        -1f
+                    },
+                label = "offset",
+            )
+
+        startContent(
+            Modifier.fillMaxHeight().weight(1f).graphicsLayer {
+                translationX = size.width * animatedOffset
+                alpha = animatedAlpha(animatedOffset)
+            }
+        )
+
+        Box(
+            modifier =
+                Modifier.fillMaxHeight().weight(1f).graphicsLayer {
+                    // A negative sign is used to make sure this is offset in the direction that's
+                    // opposite of the direction that the user switcher is pushed in.
+                    translationX = -size.width * animatedOffset
+                    alpha = animatedAlpha(animatedOffset)
+                }
+        ) {
+            endContent(Modifier.widthIn(max = 400.dp).align(Alignment.BottomCenter))
+        }
+    }
+}
+
+/**
+ * Arranges the bouncer contents and user switcher contents side-by-side, supporting a double tap
+ * anywhere on the background to flip their positions.
+ *
+ * In situations when [isUserSwitcherVisible] is `false`, one of two things may happen: either the
+ * UI for the bouncer will be shown on its own, taking up one side, with the other side just being
+ * empty space or, if that kind of "stand-alone side-by-side" isn't supported, the standard
+ * rendering of the bouncer will be used instead of the side-by-side layout.
+ */
+@Composable
+private fun SideBySideLayout(
+    viewModel: BouncerViewModel,
+    dialogFactory: BouncerDialogFactory,
+    isUserSwitcherVisible: Boolean,
+    modifier: Modifier = Modifier,
+) {
+    SwappableLayout(
+        startContent = { startContentModifier ->
+            if (isUserSwitcherVisible) {
+                UserSwitcher(
+                    viewModel = viewModel,
+                    modifier = startContentModifier,
+                )
+            } else {
+                Box(
+                    modifier = startContentModifier,
+                )
+            }
+        },
+        endContent = { endContentModifier ->
+            StandardLayout(
+                viewModel = viewModel,
+                dialogFactory = dialogFactory,
+                modifier = endContentModifier,
+            )
+        },
+        modifier = modifier,
+    )
+}
+
+/** Arranges the bouncer contents and user switcher contents one on top of the other, vertically. */
+@Composable
+private fun StackedLayout(
+    viewModel: BouncerViewModel,
+    dialogFactory: BouncerDialogFactory,
+    isUserSwitcherVisible: Boolean,
+    modifier: Modifier = Modifier,
+) {
+    Column(
+        modifier = modifier,
+    ) {
+        if (isUserSwitcherVisible) {
+            UserSwitcher(
+                viewModel = viewModel,
+                modifier = Modifier.fillMaxWidth().weight(1f),
+            )
+        }
+
+        StandardLayout(
+            viewModel = viewModel,
+            dialogFactory = dialogFactory,
+            modifier = Modifier.fillMaxWidth().weight(1f),
+        )
+    }
+}
+
+interface BouncerDialogFactory {
+    operator fun invoke(): AlertDialog
+}
+
+/** Enumerates all supported user-input area visibilities. */
+private enum class UserInputAreaVisibility {
+    /**
+     * Only the area where the user enters the input is shown; the area where the input is reflected
+     * back to the user is not shown.
+     */
+    INPUT_ONLY,
+    /**
+     * Only the area where the input is reflected back to the user is shown; the area where the
+     * input is entered by the user is not shown.
+     */
+    OUTPUT_ONLY,
+}
+
+/**
+ * Calculates an alpha for the user switcher and bouncer such that it's at `1` when the offset of
+ * the two reaches a stopping point but `0` in the middle of the transition.
+ */
+private fun animatedAlpha(
+    offset: Float,
+): Float {
+    // Describes a curve that is made of two parabolic U-shaped curves mirrored horizontally around
+    // the y-axis. The U on the left runs between x = -1 and x = 0 while the U on the right runs
+    // between x = 0 and x = 1.
+    //
+    // The minimum values of the curves are at -0.5 and +0.5.
+    //
+    // Both U curves are vertically scaled such that they reach the points (-1, 1) and (1, 1).
+    //
+    // Breaking it down, it's y = a×(|x|-m)²+b, where:
+    // x: the offset
+    // y: the alpha
+    // m: x-axis center of the parabolic curves, where the minima are.
+    // b: y-axis offset to apply to the entire curve so the animation spends more time with alpha =
+    // 0.
+    // a: amplitude to scale the parabolic curves to reach y = 1 at x = -1, x = 0, and x = +1.
+    val m = 0.5f
+    val b = -0.25
+    val a = (1 - b) / m.pow(2)
+
+    return max(0f, (a * (abs(offset) - m).pow(2) + b).toFloat())
+}
+
+private val SelectedUserImageSize = 190.dp
+private val UserSwitcherDropdownWidth = SelectedUserImageSize + 2 * 29.dp
+private val UserSwitcherDropdownHeight = 60.dp
+
+private object SceneKeys {
+    val ContiguousSceneKey = SceneKey("default")
+    val SplitSceneKey = SceneKey("split")
+}
+
+private object SceneElements {
+    val AboveFold = ElementKey("above_fold")
+    val BelowFold = ElementKey("below_fold")
+}
+
+private val SceneTransitions = transitions {
+    from(SceneKeys.ContiguousSceneKey, to = SceneKeys.SplitSceneKey) { spec = tween() }
+}
diff --git a/packages/SystemUI/compose/features/src/com/android/systemui/bouncer/ui/composable/BouncerScene.kt b/packages/SystemUI/compose/features/src/com/android/systemui/bouncer/ui/composable/BouncerScene.kt
index 57af2ba..d638ffe 100644
--- a/packages/SystemUI/compose/features/src/com/android/systemui/bouncer/ui/composable/BouncerScene.kt
+++ b/packages/SystemUI/compose/features/src/com/android/systemui/bouncer/ui/composable/BouncerScene.kt
@@ -16,91 +16,22 @@
 
 package com.android.systemui.bouncer.ui.composable
 
-import android.app.AlertDialog
-import android.app.Dialog
-import android.content.DialogInterface
-import androidx.compose.animation.Crossfade
-import androidx.compose.animation.core.animateFloatAsState
-import androidx.compose.animation.core.snap
-import androidx.compose.animation.core.tween
 import androidx.compose.foundation.Canvas
-import androidx.compose.foundation.ExperimentalFoundationApi
-import androidx.compose.foundation.Image
-import androidx.compose.foundation.combinedClickable
-import androidx.compose.foundation.gestures.detectTapGestures
-import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
-import androidx.compose.foundation.layout.Column
-import androidx.compose.foundation.layout.Row
-import androidx.compose.foundation.layout.Spacer
-import androidx.compose.foundation.layout.aspectRatio
-import androidx.compose.foundation.layout.fillMaxHeight
 import androidx.compose.foundation.layout.fillMaxSize
-import androidx.compose.foundation.layout.fillMaxWidth
-import androidx.compose.foundation.layout.height
-import androidx.compose.foundation.layout.heightIn
-import androidx.compose.foundation.layout.padding
-import androidx.compose.foundation.layout.size
-import androidx.compose.foundation.layout.width
-import androidx.compose.foundation.layout.widthIn
-import androidx.compose.foundation.shape.RoundedCornerShape
-import androidx.compose.material.icons.Icons
-import androidx.compose.material.icons.filled.KeyboardArrowDown
-import androidx.compose.material3.Button
-import androidx.compose.material3.ButtonDefaults
-import androidx.compose.material3.DropdownMenu
-import androidx.compose.material3.DropdownMenuItem
-import androidx.compose.material3.Icon
 import androidx.compose.material3.MaterialTheme
-import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
-import androidx.compose.runtime.collectAsState
-import androidx.compose.runtime.getValue
-import androidx.compose.runtime.mutableStateOf
-import androidx.compose.runtime.remember
-import androidx.compose.runtime.saveable.rememberSaveable
-import androidx.compose.runtime.setValue
-import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.graphics.asImageBitmap
-import androidx.compose.ui.graphics.graphicsLayer
-import androidx.compose.ui.input.pointer.pointerInput
-import androidx.compose.ui.platform.LocalContext
-import androidx.compose.ui.platform.LocalLayoutDirection
-import androidx.compose.ui.text.style.TextOverflow
-import androidx.compose.ui.unit.DpOffset
-import androidx.compose.ui.unit.LayoutDirection
-import androidx.compose.ui.unit.dp
-import androidx.compose.ui.unit.times
-import com.android.compose.PlatformButton
 import com.android.compose.animation.scene.ElementKey
-import com.android.compose.animation.scene.SceneKey as SceneTransitionLayoutSceneKey
 import com.android.compose.animation.scene.SceneScope
-import com.android.compose.animation.scene.SceneTransitionLayout
-import com.android.compose.animation.scene.transitions
-import com.android.compose.modifiers.thenIf
-import com.android.systemui.bouncer.shared.model.BouncerActionButtonModel
-import com.android.systemui.bouncer.ui.helper.BouncerSceneLayout
-import com.android.systemui.bouncer.ui.viewmodel.AuthMethodBouncerViewModel
 import com.android.systemui.bouncer.ui.viewmodel.BouncerViewModel
-import com.android.systemui.bouncer.ui.viewmodel.PasswordBouncerViewModel
-import com.android.systemui.bouncer.ui.viewmodel.PatternBouncerViewModel
-import com.android.systemui.bouncer.ui.viewmodel.PinBouncerViewModel
-import com.android.systemui.common.shared.model.Text.Companion.loadText
-import com.android.systemui.common.ui.compose.Icon
 import com.android.systemui.dagger.SysUISingleton
-import com.android.systemui.fold.ui.composable.foldPosture
-import com.android.systemui.fold.ui.helper.FoldPosture
-import com.android.systemui.res.R
 import com.android.systemui.scene.shared.model.Direction
 import com.android.systemui.scene.shared.model.SceneKey
 import com.android.systemui.scene.shared.model.SceneModel
 import com.android.systemui.scene.shared.model.UserAction
 import com.android.systemui.scene.ui.composable.ComposableScene
 import javax.inject.Inject
-import kotlin.math.abs
-import kotlin.math.max
-import kotlin.math.pow
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
@@ -118,7 +49,7 @@
 @Inject
 constructor(
     private val viewModel: BouncerViewModel,
-    private val dialogFactory: BouncerSceneDialogFactory,
+    private val dialogFactory: BouncerDialogFactory,
 ) : ComposableScene {
     override val key = SceneKey.Bouncer
 
@@ -140,648 +71,22 @@
 @Composable
 private fun SceneScope.BouncerScene(
     viewModel: BouncerViewModel,
-    dialogFactory: BouncerSceneDialogFactory,
+    dialogFactory: BouncerDialogFactory,
     modifier: Modifier = Modifier,
 ) {
     val backgroundColor = MaterialTheme.colorScheme.surface
-    val isSideBySideSupported by viewModel.isSideBySideSupported.collectAsState()
-    val layout = calculateLayout(isSideBySideSupported = isSideBySideSupported)
 
     Box(modifier) {
         Canvas(Modifier.element(Bouncer.Elements.Background).fillMaxSize()) {
             drawRect(color = backgroundColor)
         }
 
-        val childModifier = Modifier.element(Bouncer.Elements.Content).fillMaxSize()
-        val isFullScreenUserSwitcherEnabled = viewModel.isUserSwitcherVisible
-
-        when (layout) {
-            BouncerSceneLayout.STANDARD ->
-                StandardLayout(
-                    viewModel = viewModel,
-                    dialogFactory = dialogFactory,
-                    modifier = childModifier,
-                )
-            BouncerSceneLayout.SIDE_BY_SIDE ->
-                SideBySideLayout(
-                    viewModel = viewModel,
-                    dialogFactory = dialogFactory,
-                    isUserSwitcherVisible = isFullScreenUserSwitcherEnabled,
-                    modifier = childModifier,
-                )
-            BouncerSceneLayout.STACKED ->
-                StackedLayout(
-                    viewModel = viewModel,
-                    dialogFactory = dialogFactory,
-                    isUserSwitcherVisible = isFullScreenUserSwitcherEnabled,
-                    modifier = childModifier,
-                )
-            BouncerSceneLayout.SPLIT ->
-                SplitLayout(
-                    viewModel = viewModel,
-                    dialogFactory = dialogFactory,
-                    modifier = childModifier,
-                )
-        }
-    }
-}
-
-/**
- * Renders the contents of the actual bouncer UI, the area that takes user input to do an
- * authentication attempt, including all messaging UI (directives, reasoning, errors, etc.).
- */
-@Composable
-private fun StandardLayout(
-    viewModel: BouncerViewModel,
-    dialogFactory: BouncerSceneDialogFactory,
-    modifier: Modifier = Modifier,
-    outputOnly: Boolean = false,
-) {
-    val foldPosture: FoldPosture by foldPosture()
-    val isSplitAroundTheFoldRequired by viewModel.isFoldSplitRequired.collectAsState()
-    val isSplitAroundTheFold =
-        foldPosture == FoldPosture.Tabletop && !outputOnly && isSplitAroundTheFoldRequired
-    val currentSceneKey =
-        if (isSplitAroundTheFold) SceneKeys.SplitSceneKey else SceneKeys.ContiguousSceneKey
-
-    SceneTransitionLayout(
-        currentScene = currentSceneKey,
-        onChangeScene = {},
-        transitions = SceneTransitions,
-        modifier = modifier,
-    ) {
-        scene(SceneKeys.ContiguousSceneKey) {
-            FoldSplittable(
-                viewModel = viewModel,
-                dialogFactory = dialogFactory,
-                outputOnly = outputOnly,
-                isSplit = false,
-            )
-        }
-
-        scene(SceneKeys.SplitSceneKey) {
-            FoldSplittable(
-                viewModel = viewModel,
-                dialogFactory = dialogFactory,
-                outputOnly = outputOnly,
-                isSplit = true,
-            )
-        }
-    }
-}
-
-/**
- * Renders the "standard" layout of the bouncer, where the bouncer is rendered on its own (no user
- * switcher UI) and laid out vertically, centered horizontally.
- *
- * If [isSplit] is `true`, the top and bottom parts of the bouncer are split such that they don't
- * render across the location of the fold hardware when the device is fully or part-way unfolded
- * with the fold hinge in a horizontal position.
- *
- * If [outputOnly] is `true`, only the "output" part of the UI is shown (where the entered PIN
- * "shapes" appear), if `false`, the entire UI is shown, including the area where the user can enter
- * their PIN or pattern.
- */
-@Composable
-private fun SceneScope.FoldSplittable(
-    viewModel: BouncerViewModel,
-    dialogFactory: BouncerSceneDialogFactory,
-    outputOnly: Boolean,
-    isSplit: Boolean,
-    modifier: Modifier = Modifier,
-) {
-    val message: BouncerViewModel.MessageViewModel by viewModel.message.collectAsState()
-    val dialogMessage: String? by viewModel.throttlingDialogMessage.collectAsState()
-    var dialog: Dialog? by remember { mutableStateOf(null) }
-    val actionButton: BouncerActionButtonModel? by viewModel.actionButton.collectAsState()
-    val splitRatio =
-        LocalContext.current.resources.getFloat(
-            R.dimen.motion_layout_half_fold_bouncer_height_ratio
-        )
-
-    Column(modifier = modifier.padding(horizontal = 32.dp)) {
-        // Content above the fold, when split on a foldable device in a "table top" posture:
-        Box(
-            modifier =
-                Modifier.element(SceneElements.AboveFold).fillMaxWidth().thenIf(isSplit) {
-                    Modifier.weight(splitRatio)
-                },
-        ) {
-            Column(
-                horizontalAlignment = Alignment.CenterHorizontally,
-                modifier = Modifier.fillMaxWidth().padding(top = 92.dp),
-            ) {
-                Crossfade(
-                    targetState = message,
-                    label = "Bouncer message",
-                    animationSpec = if (message.isUpdateAnimated) tween() else snap(),
-                ) { message ->
-                    Text(
-                        text = message.text,
-                        color = MaterialTheme.colorScheme.onSurface,
-                        style = MaterialTheme.typography.bodyLarge,
-                    )
-                }
-
-                Spacer(Modifier.heightIn(min = 21.dp, max = 48.dp))
-
-                UserInputArea(
-                    viewModel = viewModel,
-                    visibility = UserInputAreaVisibility.OUTPUT_ONLY,
-                )
-            }
-        }
-
-        // Content below the fold, when split on a foldable device in a "table top" posture:
-        Box(
-            modifier =
-                Modifier.element(SceneElements.BelowFold).fillMaxWidth().thenIf(isSplit) {
-                    Modifier.weight(1 - splitRatio)
-                },
-        ) {
-            Column(
-                horizontalAlignment = Alignment.CenterHorizontally,
-                modifier = Modifier.fillMaxWidth(),
-            ) {
-                if (!outputOnly) {
-                    Box(Modifier.weight(1f)) {
-                        UserInputArea(
-                            viewModel = viewModel,
-                            visibility = UserInputAreaVisibility.INPUT_ONLY,
-                            modifier = Modifier.align(Alignment.Center),
-                        )
-                    }
-                }
-
-                Spacer(Modifier.heightIn(min = 21.dp, max = 48.dp))
-
-                val actionButtonModifier = Modifier.height(56.dp)
-
-                actionButton.let { actionButtonViewModel ->
-                    if (actionButtonViewModel != null) {
-                        BouncerActionButton(
-                            viewModel = actionButtonViewModel,
-                            modifier = actionButtonModifier,
-                        )
-                    } else {
-                        Spacer(modifier = actionButtonModifier)
-                    }
-                }
-
-                Spacer(Modifier.height(48.dp))
-            }
-        }
-
-        if (dialogMessage != null) {
-            if (dialog == null) {
-                dialog =
-                    dialogFactory().apply {
-                        setMessage(dialogMessage)
-                        setButton(
-                            DialogInterface.BUTTON_NEUTRAL,
-                            context.getString(R.string.ok),
-                        ) { _, _ ->
-                            viewModel.onThrottlingDialogDismissed()
-                        }
-                        setCancelable(false)
-                        setCanceledOnTouchOutside(false)
-                        show()
-                    }
-            }
-        } else {
-            dialog?.dismiss()
-            dialog = null
-        }
-    }
-}
-
-/**
- * Renders the user input area, where the user interacts with the UI to enter their credentials.
- *
- * For example, this can be the pattern input area, the password text box, or pin pad.
- */
-@Composable
-private fun UserInputArea(
-    viewModel: BouncerViewModel,
-    visibility: UserInputAreaVisibility,
-    modifier: Modifier = Modifier,
-) {
-    val authMethodViewModel: AuthMethodBouncerViewModel? by
-        viewModel.authMethodViewModel.collectAsState()
-
-    when (val nonNullViewModel = authMethodViewModel) {
-        is PinBouncerViewModel ->
-            when (visibility) {
-                UserInputAreaVisibility.OUTPUT_ONLY ->
-                    PinInputDisplay(
-                        viewModel = nonNullViewModel,
-                        modifier = modifier,
-                    )
-                UserInputAreaVisibility.INPUT_ONLY ->
-                    PinPad(
-                        viewModel = nonNullViewModel,
-                        modifier = modifier,
-                    )
-            }
-        is PasswordBouncerViewModel ->
-            if (visibility == UserInputAreaVisibility.INPUT_ONLY) {
-                PasswordBouncer(
-                    viewModel = nonNullViewModel,
-                    modifier = modifier,
-                )
-            }
-        is PatternBouncerViewModel ->
-            if (visibility == UserInputAreaVisibility.INPUT_ONLY) {
-                PatternBouncer(
-                    viewModel = nonNullViewModel,
-                    modifier = modifier.aspectRatio(1f, matchHeightConstraintsFirst = false)
-                )
-            }
-        else -> Unit
-    }
-}
-
-/**
- * Renders the action button on the bouncer, which triggers either Return to Call or Emergency Call.
- */
-@OptIn(ExperimentalFoundationApi::class)
-@Composable
-private fun BouncerActionButton(
-    viewModel: BouncerActionButtonModel,
-    modifier: Modifier = Modifier,
-) {
-    Button(
-        onClick = viewModel.onClick,
-        modifier =
-            modifier.thenIf(viewModel.onLongClick != null) {
-                Modifier.combinedClickable(
-                    onClick = viewModel.onClick,
-                    onLongClick = viewModel.onLongClick,
-                )
-            },
-        colors =
-            ButtonDefaults.buttonColors(
-                containerColor = MaterialTheme.colorScheme.tertiaryContainer,
-                contentColor = MaterialTheme.colorScheme.onTertiaryContainer,
-            ),
-    ) {
-        Text(
-            text = viewModel.label,
-            style = MaterialTheme.typography.bodyMedium,
+        // Separate the bouncer content into a reusable composable that doesn't have any SceneScope
+        // dependencies
+        BouncerContent(
+            viewModel,
+            dialogFactory,
+            Modifier.element(Bouncer.Elements.Content).fillMaxSize()
         )
     }
 }
-
-/** Renders the UI of the user switcher that's displayed on large screens next to the bouncer UI. */
-@Composable
-private fun UserSwitcher(
-    viewModel: BouncerViewModel,
-    modifier: Modifier = Modifier,
-) {
-    val selectedUserImage by viewModel.selectedUserImage.collectAsState(null)
-    val dropdownItems by viewModel.userSwitcherDropdown.collectAsState(emptyList())
-
-    Column(
-        horizontalAlignment = Alignment.CenterHorizontally,
-        verticalArrangement = Arrangement.Center,
-        modifier = modifier,
-    ) {
-        selectedUserImage?.let {
-            Image(
-                bitmap = it.asImageBitmap(),
-                contentDescription = null,
-                modifier = Modifier.size(SelectedUserImageSize),
-            )
-        }
-
-        val (isDropdownExpanded, setDropdownExpanded) = remember { mutableStateOf(false) }
-
-        dropdownItems.firstOrNull()?.let { firstDropdownItem ->
-            Spacer(modifier = Modifier.height(40.dp))
-
-            Box {
-                PlatformButton(
-                    modifier =
-                        Modifier
-                            // Remove the built-in padding applied inside PlatformButton:
-                            .padding(vertical = 0.dp)
-                            .width(UserSwitcherDropdownWidth)
-                            .height(UserSwitcherDropdownHeight),
-                    colors =
-                        ButtonDefaults.buttonColors(
-                            containerColor = MaterialTheme.colorScheme.surfaceContainerHighest,
-                            contentColor = MaterialTheme.colorScheme.onSurface,
-                        ),
-                    onClick = { setDropdownExpanded(!isDropdownExpanded) },
-                ) {
-                    val context = LocalContext.current
-                    Text(
-                        text = checkNotNull(firstDropdownItem.text.loadText(context)),
-                        style = MaterialTheme.typography.headlineSmall,
-                        maxLines = 1,
-                        overflow = TextOverflow.Ellipsis,
-                    )
-
-                    Spacer(modifier = Modifier.weight(1f))
-
-                    Icon(
-                        imageVector = Icons.Default.KeyboardArrowDown,
-                        contentDescription = null,
-                        modifier = Modifier.size(32.dp),
-                    )
-                }
-
-                UserSwitcherDropdownMenu(
-                    isExpanded = isDropdownExpanded,
-                    items = dropdownItems,
-                    onDismissed = { setDropdownExpanded(false) },
-                )
-            }
-        }
-    }
-}
-
-/**
- * Renders the dropdowm menu that displays the actual users and/or user actions that can be
- * selected.
- */
-@Composable
-private fun UserSwitcherDropdownMenu(
-    isExpanded: Boolean,
-    items: List<BouncerViewModel.UserSwitcherDropdownItemViewModel>,
-    onDismissed: () -> Unit,
-) {
-    val context = LocalContext.current
-
-    // TODO(b/303071855): once the FR is fixed, remove this composition local override.
-    MaterialTheme(
-        colorScheme =
-            MaterialTheme.colorScheme.copy(
-                surface = MaterialTheme.colorScheme.surfaceContainerHighest,
-            ),
-        shapes = MaterialTheme.shapes.copy(extraSmall = RoundedCornerShape(28.dp)),
-    ) {
-        DropdownMenu(
-            expanded = isExpanded,
-            onDismissRequest = onDismissed,
-            offset =
-                DpOffset(
-                    x = 0.dp,
-                    y = -UserSwitcherDropdownHeight,
-                ),
-            modifier = Modifier.width(UserSwitcherDropdownWidth),
-        ) {
-            items.forEach { userSwitcherDropdownItem ->
-                DropdownMenuItem(
-                    leadingIcon = {
-                        Icon(
-                            icon = userSwitcherDropdownItem.icon,
-                            tint = MaterialTheme.colorScheme.primary,
-                            modifier = Modifier.size(28.dp),
-                        )
-                    },
-                    text = {
-                        Text(
-                            text = checkNotNull(userSwitcherDropdownItem.text.loadText(context)),
-                            style = MaterialTheme.typography.bodyLarge,
-                            color = MaterialTheme.colorScheme.onSurface,
-                        )
-                    },
-                    onClick = {
-                        onDismissed()
-                        userSwitcherDropdownItem.onClick()
-                    },
-                )
-            }
-        }
-    }
-}
-
-/**
- * Renders the bouncer UI in split mode, with half on one side and half on the other side, swappable
- * by double-tapping on the side.
- */
-@Composable
-private fun SplitLayout(
-    viewModel: BouncerViewModel,
-    dialogFactory: BouncerSceneDialogFactory,
-    modifier: Modifier = Modifier,
-) {
-    SwappableLayout(
-        startContent = { startContentModifier ->
-            StandardLayout(
-                viewModel = viewModel,
-                dialogFactory = dialogFactory,
-                outputOnly = true,
-                modifier = startContentModifier,
-            )
-        },
-        endContent = { endContentModifier ->
-            UserInputArea(
-                viewModel = viewModel,
-                visibility = UserInputAreaVisibility.INPUT_ONLY,
-                modifier = endContentModifier,
-            )
-        },
-        modifier = modifier
-    )
-}
-
-/**
- * Arranges the given two contents side-by-side, supporting a double tap anywhere on the background
- * to flip their positions.
- */
-@Composable
-private fun SwappableLayout(
-    startContent: @Composable (Modifier) -> Unit,
-    endContent: @Composable (Modifier) -> Unit,
-    modifier: Modifier = Modifier,
-) {
-    val layoutDirection = LocalLayoutDirection.current
-    val isLeftToRight = layoutDirection == LayoutDirection.Ltr
-    val (isSwapped, setSwapped) = rememberSaveable(isLeftToRight) { mutableStateOf(!isLeftToRight) }
-
-    Row(
-        modifier =
-            modifier.pointerInput(Unit) {
-                detectTapGestures(
-                    onDoubleTap = { offset ->
-                        // Depending on where the user double tapped, switch the elements such that
-                        // the endContent is closer to the side that was double tapped.
-                        setSwapped(offset.x < size.width / 2)
-                    }
-                )
-            },
-    ) {
-        val animatedOffset by
-            animateFloatAsState(
-                targetValue =
-                    if (!isSwapped) {
-                        // When startContent is first, both elements have their natural placement so
-                        // they are not offset in any way.
-                        0f
-                    } else if (isLeftToRight) {
-                        // Since startContent is not first, the elements have to be swapped
-                        // horizontally. In the case of LTR locales, this means pushing startContent
-                        // to the right, hence the positive number.
-                        1f
-                    } else {
-                        // Since startContent is not first, the elements have to be swapped
-                        // horizontally. In the case of RTL locales, this means pushing startContent
-                        // to the left, hence the negative number.
-                        -1f
-                    },
-                label = "offset",
-            )
-
-        startContent(
-            Modifier.fillMaxHeight().weight(1f).graphicsLayer {
-                translationX = size.width * animatedOffset
-                alpha = animatedAlpha(animatedOffset)
-            }
-        )
-
-        Box(
-            modifier =
-                Modifier.fillMaxHeight().weight(1f).graphicsLayer {
-                    // A negative sign is used to make sure this is offset in the direction that's
-                    // opposite of the direction that the user switcher is pushed in.
-                    translationX = -size.width * animatedOffset
-                    alpha = animatedAlpha(animatedOffset)
-                }
-        ) {
-            endContent(Modifier.widthIn(max = 400.dp).align(Alignment.BottomCenter))
-        }
-    }
-}
-
-/**
- * Arranges the bouncer contents and user switcher contents side-by-side, supporting a double tap
- * anywhere on the background to flip their positions.
- *
- * In situations when [isUserSwitcherVisible] is `false`, one of two things may happen: either the
- * UI for the bouncer will be shown on its own, taking up one side, with the other side just being
- * empty space or, if that kind of "stand-alone side-by-side" isn't supported, the standard
- * rendering of the bouncer will be used instead of the side-by-side layout.
- */
-@Composable
-private fun SideBySideLayout(
-    viewModel: BouncerViewModel,
-    dialogFactory: BouncerSceneDialogFactory,
-    isUserSwitcherVisible: Boolean,
-    modifier: Modifier = Modifier,
-) {
-    SwappableLayout(
-        startContent = { startContentModifier ->
-            if (isUserSwitcherVisible) {
-                UserSwitcher(
-                    viewModel = viewModel,
-                    modifier = startContentModifier,
-                )
-            } else {
-                Box(
-                    modifier = startContentModifier,
-                )
-            }
-        },
-        endContent = { endContentModifier ->
-            StandardLayout(
-                viewModel = viewModel,
-                dialogFactory = dialogFactory,
-                modifier = endContentModifier,
-            )
-        },
-        modifier = modifier,
-    )
-}
-
-/** Arranges the bouncer contents and user switcher contents one on top of the other, vertically. */
-@Composable
-private fun StackedLayout(
-    viewModel: BouncerViewModel,
-    dialogFactory: BouncerSceneDialogFactory,
-    isUserSwitcherVisible: Boolean,
-    modifier: Modifier = Modifier,
-) {
-    Column(
-        modifier = modifier,
-    ) {
-        if (isUserSwitcherVisible) {
-            UserSwitcher(
-                viewModel = viewModel,
-                modifier = Modifier.fillMaxWidth().weight(1f),
-            )
-        }
-
-        StandardLayout(
-            viewModel = viewModel,
-            dialogFactory = dialogFactory,
-            modifier = Modifier.fillMaxWidth().weight(1f),
-        )
-    }
-}
-
-interface BouncerSceneDialogFactory {
-    operator fun invoke(): AlertDialog
-}
-
-/** Enumerates all supported user-input area visibilities. */
-private enum class UserInputAreaVisibility {
-    /**
-     * Only the area where the user enters the input is shown; the area where the input is reflected
-     * back to the user is not shown.
-     */
-    INPUT_ONLY,
-    /**
-     * Only the area where the input is reflected back to the user is shown; the area where the
-     * input is entered by the user is not shown.
-     */
-    OUTPUT_ONLY,
-}
-
-/**
- * Calculates an alpha for the user switcher and bouncer such that it's at `1` when the offset of
- * the two reaches a stopping point but `0` in the middle of the transition.
- */
-private fun animatedAlpha(
-    offset: Float,
-): Float {
-    // Describes a curve that is made of two parabolic U-shaped curves mirrored horizontally around
-    // the y-axis. The U on the left runs between x = -1 and x = 0 while the U on the right runs
-    // between x = 0 and x = 1.
-    //
-    // The minimum values of the curves are at -0.5 and +0.5.
-    //
-    // Both U curves are vertically scaled such that they reach the points (-1, 1) and (1, 1).
-    //
-    // Breaking it down, it's y = a×(|x|-m)²+b, where:
-    // x: the offset
-    // y: the alpha
-    // m: x-axis center of the parabolic curves, where the minima are.
-    // b: y-axis offset to apply to the entire curve so the animation spends more time with alpha =
-    // 0.
-    // a: amplitude to scale the parabolic curves to reach y = 1 at x = -1, x = 0, and x = +1.
-    val m = 0.5f
-    val b = -0.25
-    val a = (1 - b) / m.pow(2)
-
-    return max(0f, (a * (abs(offset) - m).pow(2) + b).toFloat())
-}
-
-private val SelectedUserImageSize = 190.dp
-private val UserSwitcherDropdownWidth = SelectedUserImageSize + 2 * 29.dp
-private val UserSwitcherDropdownHeight = 60.dp
-
-private object SceneKeys {
-    val ContiguousSceneKey = SceneTransitionLayoutSceneKey("default")
-    val SplitSceneKey = SceneTransitionLayoutSceneKey("split")
-}
-
-private object SceneElements {
-    val AboveFold = ElementKey("above_fold")
-    val BelowFold = ElementKey("below_fold")
-}
-
-private val SceneTransitions = transitions {
-    from(SceneKeys.ContiguousSceneKey, to = SceneKeys.SplitSceneKey) { spec = tween() }
-}