Merge "[flexiglass] Scroll the shade with TalkBack" into main

11 files changed, 270 insertions, 57 deletions

diff --git a/packages/SystemUI/compose/features/src/com/android/systemui/notifications/ui/composable/Notifications.kt b/packages/SystemUI/compose/features/src/com/android/systemui/notifications/ui/composable/Notifications.kt
index 4c6834cf6bea..834a7f5220ab 100644
--- a/packages/SystemUI/compose/features/src/com/android/systemui/notifications/ui/composable/Notifications.kt
+++ b/packages/SystemUI/compose/features/src/com/android/systemui/notifications/ui/composable/Notifications.kt
@@ -50,9 +50,11 @@ import androidx.compose.material3.MaterialTheme
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.derivedStateOf
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableFloatStateOf
 import androidx.compose.runtime.mutableIntStateOf
+import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.runtime.setValue
@@ -60,6 +62,7 @@ import androidx.compose.runtime.snapshotFlow
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.drawBehind
+import androidx.compose.ui.geometry.Rect
 import androidx.compose.ui.graphics.BlendMode
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.graphicsLayer
@@ -95,13 +98,17 @@ import com.android.systemui.scene.shared.model.Overlays
 import com.android.systemui.scene.shared.model.Scenes
 import com.android.systemui.shade.shared.flag.DualShade
 import com.android.systemui.shade.ui.composable.ShadeHeader
+import com.android.systemui.statusbar.notification.stack.shared.model.AccessibilityScrollEvent
 import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrimBounds
 import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrimRounding
+import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrollState
 import com.android.systemui.statusbar.notification.stack.ui.view.NotificationScrollView
 import com.android.systemui.statusbar.notification.stack.ui.viewmodel.NotificationTransitionThresholds.EXPANSION_FOR_MAX_CORNER_RADIUS
 import com.android.systemui.statusbar.notification.stack.ui.viewmodel.NotificationTransitionThresholds.EXPANSION_FOR_MAX_SCRIM_ALPHA
 import com.android.systemui.statusbar.notification.stack.ui.viewmodel.NotificationsPlaceholderViewModel
+import kotlin.math.max
 import kotlin.math.roundToInt
+import kotlinx.coroutines.awaitCancellation
 import kotlinx.coroutines.coroutineScope
 import kotlinx.coroutines.launch
 
@@ -315,6 +322,12 @@ fun SceneScope.NotificationScrollingStack(
      */
     val stackHeight = remember { mutableIntStateOf(0) }
 
+    /**
+     * Space available for the notification stack on the screen. These bounds don't scroll off the
+     * screen, and respect the scrim paddings, scrim clipping.
+     */
+    val stackBoundsOnScreen = remember { mutableStateOf(Rect.Zero) }
+
     val scrimRounding =
         viewModel.shadeScrimRounding.collectAsStateWithLifecycle(ShadeScrimRounding())
 
@@ -348,12 +361,19 @@ fun SceneScope.NotificationScrollingStack(
     // The top y bound of the IME.
     val imeTop = remember { mutableFloatStateOf(0f) }
 
-    // we are not scrolled to the top unless the scrim is at its maximum offset.
-    LaunchedEffect(viewModel, scrimOffset) {
-        snapshotFlow { scrimOffset.value >= 0f }
-            .collect { isScrolledToTop -> viewModel.setScrolledToTop(isScrolledToTop) }
+    val shadeScrollState by remember {
+        derivedStateOf {
+            ShadeScrollState(
+                // we are not scrolled to the top unless the scrim is at its maximum offset.
+                isScrolledToTop = scrimOffset.value >= 0f,
+                scrollPosition = scrollState.value,
+                maxScrollPosition = scrollState.maxValue,
+            )
+        }
     }
 
+    LaunchedEffect(shadeScrollState) { viewModel.setScrollState(shadeScrollState) }
+
     // if contentHeight drops below minimum visible scrim height while scrim is
     // expanded, reset scrim offset.
     LaunchedEffect(stackHeight, scrimOffset) {
@@ -395,6 +415,38 @@ fun SceneScope.NotificationScrollingStack(
             }
     }
 
+    // TalkBack sends a scroll event, when it wants to navigate to an item that is not displayed in
+    // the current viewport.
+    LaunchedEffect(viewModel) {
+        viewModel.setAccessibilityScrollEventConsumer { event ->
+            // scroll up, or down by the height of the visible portion of the notification stack
+            val direction =
+                when (event) {
+                    AccessibilityScrollEvent.SCROLL_UP -> -1
+                    AccessibilityScrollEvent.SCROLL_DOWN -> 1
+                }
+            val viewPortHeight = stackBoundsOnScreen.value.height
+            val scrollStep = max(0f, viewPortHeight - stackScrollView.stackBottomInset)
+            val scrollPosition = scrollState.value.toFloat()
+            val scrollRange = scrollState.maxValue.toFloat()
+            val targetScroll = (scrollPosition + direction * scrollStep).coerceIn(0f, scrollRange)
+            coroutineScope.launch {
+                scrollNotificationStack(
+                    delta = targetScroll - scrollPosition,
+                    animate = false,
+                    scrimOffset = scrimOffset,
+                    minScrimOffset = minScrimOffset,
+                    scrollState = scrollState,
+                )
+            }
+        }
+        try {
+            awaitCancellation()
+        } finally {
+            viewModel.setAccessibilityScrollEventConsumer(null)
+        }
+    }
+
     val scrimNestedScrollConnection =
         shadeSession.rememberSession(
             scrimOffset,
@@ -520,6 +572,9 @@ fun SceneScope.NotificationScrollingStack(
                         .verticalScroll(scrollState)
                         .padding(top = topPadding)
                         .fillMaxWidth()
+                        .onGloballyPositioned { coordinates ->
+                            stackBoundsOnScreen.value = coordinates.boundsInWindow()
+                        }
             ) {
                 NotificationPlaceholder(
                     stackScrollView = stackScrollView,
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/NotificationStackScrollLayout.java b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/NotificationStackScrollLayout.java
index d828a6700ee6..ec1dc0a77118 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/NotificationStackScrollLayout.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/NotificationStackScrollLayout.java
@@ -25,6 +25,8 @@ import static com.android.internal.jank.InteractionJankMonitor.CUJ_SHADE_CLEAR_A
 import static com.android.systemui.Flags.notificationOverExpansionClippingFix;
 import static com.android.systemui.statusbar.notification.stack.NotificationPriorityBucketKt.BUCKET_SILENT;
 import static com.android.systemui.statusbar.notification.stack.StackStateAnimator.ANIMATION_DURATION_SWIPE;
+import static com.android.systemui.statusbar.notification.stack.shared.model.AccessibilityScrollEvent.SCROLL_DOWN;
+import static com.android.systemui.statusbar.notification.stack.shared.model.AccessibilityScrollEvent.SCROLL_UP;
 import static com.android.systemui.util.DumpUtilsKt.println;
 import static com.android.systemui.util.DumpUtilsKt.visibilityString;
 
@@ -118,8 +120,10 @@ import com.android.systemui.statusbar.notification.shared.NotificationHeadsUpCyc
 import com.android.systemui.statusbar.notification.shared.NotificationThrottleHun;
 import com.android.systemui.statusbar.notification.shared.NotificationsImprovedHunAnimation;
 import com.android.systemui.statusbar.notification.shared.NotificationsLiveDataStoreRefactor;
+import com.android.systemui.statusbar.notification.stack.shared.model.AccessibilityScrollEvent;
 import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrimBounds;
 import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrimShape;
+import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrollState;
 import com.android.systemui.statusbar.notification.stack.ui.view.NotificationScrollView;
 import com.android.systemui.statusbar.phone.HeadsUpAppearanceController;
 import com.android.systemui.statusbar.phone.ScreenOffAnimationController;
@@ -609,7 +613,7 @@ public class NotificationStackScrollLayout
         @Override
         public boolean isScrolledToTop() {
             if (SceneContainerFlag.isEnabled()) {
-                return mScrollViewFields.isScrolledToTop();
+                return mScrollViewFields.getScrollState().isScrolledToTop();
             } else {
                 return mOwnScrollY == 0;
             }
@@ -1247,9 +1251,25 @@ public class NotificationStackScrollLayout
     }
 
     @Override
-    public void setScrolledToTop(boolean scrolledToTop) {
-        if (SceneContainerFlag.isUnexpectedlyInLegacyMode()) return;
-        mScrollViewFields.setScrolledToTop(scrolledToTop);
+    public void setScrollState(@NonNull ShadeScrollState scrollState) {
+        if (SceneContainerFlag.isUnexpectedlyInLegacyMode()) {
+            return;
+        }
+
+        boolean forwardScrollable =
+                scrollState.getScrollPosition() < scrollState.getMaxScrollPosition();
+        boolean backwardScrollable = scrollState.getScrollPosition() > 0;
+        mScrollable = forwardScrollable || backwardScrollable;
+        mForwardScrollable = forwardScrollable;
+        mBackwardScrollable = backwardScrollable;
+
+        boolean scrollPositionChanged = mScrollViewFields.getScrollState().getScrollPosition()
+                != scrollState.getScrollPosition();
+        mScrollViewFields.setScrollState(scrollState);
+
+        if (scrollPositionChanged) {
+            sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_SCROLLED);
+        }
     }
 
     @Override
@@ -1295,6 +1315,12 @@ public class NotificationStackScrollLayout
     }
 
     @Override
+    public void setAccessibilityScrollEventConsumer(
+            @Nullable Consumer<AccessibilityScrollEvent> consumer) {
+        mScrollViewFields.setAccessibilityScrollEventConsumer(consumer);
+    }
+
+    @Override
     public void setCurrentGestureOverscrollConsumer(@Nullable Consumer<Boolean> consumer) {
         if (SceneContainerFlag.isUnexpectedlyInLegacyMode()) return;
         mScrollViewFields.setCurrentGestureOverscrollConsumer(consumer);
@@ -2645,6 +2671,11 @@ public class NotificationStackScrollLayout
         return mHeadsUpInset;
     }
 
+    @Override
+    public int getStackBottomInset() {
+        return mPaddingBetweenElements + mShelf.getIntrinsicHeight();
+    }
+
     /**
      * Calculate the gap height between two different views
      *
@@ -4243,17 +4274,27 @@ public class NotificationStackScrollLayout
      */
     @Override
     public boolean performAccessibilityActionInternal(int action, Bundle arguments) {
-        // Don't handle scroll accessibility events from the NSSL, when SceneContainer enabled.
-        if (SceneContainerFlag.isEnabled()) {
-            return super.performAccessibilityActionInternal(action, arguments);
-        }
-
         if (super.performAccessibilityActionInternal(action, arguments)) {
             return true;
         }
         if (!isEnabled()) {
             return false;
         }
+
+        if (SceneContainerFlag.isEnabled()) {
+            switch (action) {
+                case AccessibilityNodeInfo.ACTION_SCROLL_FORWARD:
+                case android.R.id.accessibilityActionScrollDown:
+                    mScrollViewFields.sendAccessibilityScrollEvent(SCROLL_DOWN);
+                    return true;
+                case AccessibilityNodeInfo.ACTION_SCROLL_BACKWARD:
+                case android.R.id.accessibilityActionScrollUp:
+                    mScrollViewFields.sendAccessibilityScrollEvent(SCROLL_UP);
+                    return true;
+            }
+            return false;
+        }
+
         int direction = -1;
         switch (action) {
             case AccessibilityNodeInfo.ACTION_SCROLL_FORWARD:
@@ -5029,25 +5070,21 @@ public class NotificationStackScrollLayout
     @Override
     public void onInitializeAccessibilityEventInternal(AccessibilityEvent event) {
         super.onInitializeAccessibilityEventInternal(event);
-        // Don't handle scroll accessibility events from the NSSL, when SceneContainer enabled.
-        if (SceneContainerFlag.isEnabled()) {
-            return;
-        }
-
         event.setScrollable(mScrollable);
         event.setMaxScrollX(mScrollX);
-        event.setScrollY(mOwnScrollY);
-        event.setMaxScrollY(getScrollRange());
+
+        if (SceneContainerFlag.isEnabled()) {
+            event.setScrollY(mScrollViewFields.getScrollState().getScrollPosition());
+            event.setMaxScrollY(mScrollViewFields.getScrollState().getMaxScrollPosition());
+        } else {
+            event.setScrollY(mOwnScrollY);
+            event.setMaxScrollY(getScrollRange());
+        }
     }
 
     @Override
     public void onInitializeAccessibilityNodeInfoInternal(AccessibilityNodeInfo info) {
         super.onInitializeAccessibilityNodeInfoInternal(info);
-        // Don't handle scroll accessibility events from the NSSL, when SceneContainer enabled.
-        if (SceneContainerFlag.isEnabled()) {
-            return;
-        }
-
         if (mScrollable) {
             info.setScrollable(true);
             if (mBackwardScrollable) {
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ScrollViewFields.kt b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ScrollViewFields.kt
index f6e8b8f0166b..cf6d45a8938e 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ScrollViewFields.kt
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ScrollViewFields.kt
@@ -17,7 +17,9 @@
 package com.android.systemui.statusbar.notification.stack
 
 import android.util.IndentingPrintWriter
+import com.android.systemui.statusbar.notification.stack.shared.model.AccessibilityScrollEvent
 import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrimShape
+import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrollState
 import com.android.systemui.util.printSection
 import com.android.systemui.util.println
 import java.util.function.Consumer
@@ -32,8 +34,9 @@ import java.util.function.Consumer
 class ScrollViewFields {
     /** Used to produce the clipping path */
     var scrimClippingShape: ShadeScrimShape? = null
-    /** Whether the notifications are scrolled all the way to the top (i.e. when freshly opened) */
-    var isScrolledToTop: Boolean = true
+
+    /** Scroll state of the notification shade. */
+    var scrollState: ShadeScrollState = ShadeScrollState()
 
     /**
      * Height in view pixels at which the Notification Stack would like to be laid out, including
@@ -47,6 +50,13 @@ class ScrollViewFields {
      * placeholder
      */
     var syntheticScrollConsumer: Consumer<Float>? = null
+
+    /**
+     * When the NSSL navigates through the notifications with TalkBack, it can send scroll events
+     * here, to be able to browse through the whole list of notifications in the shade.
+     */
+    var accessibilityScrollEventConsumer: Consumer<AccessibilityScrollEvent>? = null
+
     /**
      * When a gesture is consumed internally by NSSL but needs to be handled by other elements (such
      * as the notif scrim) as overscroll, we can notify the placeholder through here.
@@ -86,10 +96,15 @@ class ScrollViewFields {
     fun sendRemoteInputRowBottomBound(bottomY: Float?) =
         remoteInputRowBottomBoundConsumer?.accept(bottomY)
 
+    /** send an [AccessibilityScrollEvent] to the [accessibilityScrollEventConsumer] if present */
+    fun sendAccessibilityScrollEvent(event: AccessibilityScrollEvent) {
+        accessibilityScrollEventConsumer?.accept(event)
+    }
+
     fun dump(pw: IndentingPrintWriter) {
         pw.printSection("StackViewStates") {
             pw.println("scrimClippingShape", scrimClippingShape)
-            pw.println("isScrolledToTop", isScrolledToTop)
+            pw.println("scrollState", scrollState)
         }
     }
 }
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/data/repository/NotificationPlaceholderRepository.kt b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/data/repository/NotificationPlaceholderRepository.kt
index c0f1a5619140..5ec4c8988697 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/data/repository/NotificationPlaceholderRepository.kt
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/data/repository/NotificationPlaceholderRepository.kt
@@ -17,7 +17,10 @@
 package com.android.systemui.statusbar.notification.stack.data.repository
 
 import com.android.systemui.dagger.SysUISingleton
+import com.android.systemui.statusbar.notification.stack.shared.model.AccessibilityScrollEvent
 import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrimBounds
+import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrollState
+import java.util.function.Consumer
 import javax.inject.Inject
 import kotlinx.coroutines.flow.MutableStateFlow
 
@@ -44,9 +47,9 @@ class NotificationPlaceholderRepository @Inject constructor() {
     /** height made available to the notifications in the size-constrained mode of lock screen. */
     val constrainedAvailableSpace = MutableStateFlow(0)
 
-    /**
-     * Whether the notification stack is scrolled to the top; i.e., it cannot be scrolled down any
-     * further.
-     */
-    val scrolledToTop = MutableStateFlow(true)
+    /** Scroll state of the notification shade. */
+    val shadeScrollState = MutableStateFlow(ShadeScrollState())
+
+    /** A consumer of [AccessibilityScrollEvent]s. */
+    var accessibilityScrollEventConsumer: Consumer<AccessibilityScrollEvent>? = null
 }
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/domain/interactor/NotificationStackAppearanceInteractor.kt b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/domain/interactor/NotificationStackAppearanceInteractor.kt
index 32e092bcdf4d..d4dd1d4b9e0b 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/domain/interactor/NotificationStackAppearanceInteractor.kt
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/domain/interactor/NotificationStackAppearanceInteractor.kt
@@ -23,8 +23,11 @@ import com.android.systemui.shade.domain.interactor.ShadeInteractor
 import com.android.systemui.shade.shared.model.ShadeMode
 import com.android.systemui.statusbar.notification.stack.data.repository.NotificationPlaceholderRepository
 import com.android.systemui.statusbar.notification.stack.data.repository.NotificationViewHeightRepository
+import com.android.systemui.statusbar.notification.stack.shared.model.AccessibilityScrollEvent
 import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrimBounds
 import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrimRounding
+import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrollState
+import java.util.function.Consumer
 import javax.inject.Inject
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.StateFlow
@@ -78,11 +81,9 @@ constructor(
     val constrainedAvailableSpace: StateFlow<Int> =
         placeholderRepository.constrainedAvailableSpace.asStateFlow()
 
-    /**
-     * Whether the notification stack is scrolled to the top; i.e., it cannot be scrolled down any
-     * further.
-     */
-    val scrolledToTop: StateFlow<Boolean> = placeholderRepository.scrolledToTop.asStateFlow()
+    /** Scroll state of the notification shade. */
+    val shadeScrollState: StateFlow<ShadeScrollState> =
+        placeholderRepository.shadeScrollState.asStateFlow()
 
     /**
      * The amount in px that the notification stack should scroll due to internal expansion. This
@@ -123,9 +124,9 @@ constructor(
         placeholderRepository.shadeScrimBounds.value = bounds
     }
 
-    /** Sets whether the notification stack is scrolled to the top. */
-    fun setScrolledToTop(scrolledToTop: Boolean) {
-        placeholderRepository.scrolledToTop.value = scrolledToTop
+    /** Updates the current scroll state of the notification shade. */
+    fun setScrollState(shadeScrollState: ShadeScrollState) {
+        placeholderRepository.shadeScrollState.value = shadeScrollState
     }
 
     /** Sets the amount (px) that the notification stack should scroll due to internal expansion. */
@@ -133,6 +134,16 @@ constructor(
         viewHeightRepository.syntheticScroll.value = delta
     }
 
+    /** Sends an [AccessibilityScrollEvent] to scroll the stack up or down. */
+    fun sendAccessibilityScrollEvent(accessibilityScrollEvent: AccessibilityScrollEvent) {
+        placeholderRepository.accessibilityScrollEventConsumer?.accept(accessibilityScrollEvent)
+    }
+
+    /** Set a consumer for the [AccessibilityScrollEvent]s to be handled by the placeholder. */
+    fun setAccessibilityScrollEventConsumer(consumer: Consumer<AccessibilityScrollEvent>?) {
+        placeholderRepository.accessibilityScrollEventConsumer = consumer
+    }
+
     /** Sets whether the current touch gesture is overscroll. */
     fun setCurrentGestureOverscroll(isOverscroll: Boolean) {
         viewHeightRepository.isCurrentGestureOverscroll.value = isOverscroll
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/shared/model/AccessibilityScrollEvent.kt b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/shared/model/AccessibilityScrollEvent.kt
new file mode 100644
index 000000000000..01341e1d056d
--- /dev/null
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/shared/model/AccessibilityScrollEvent.kt
@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2024 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.statusbar.notification.stack.shared.model
+
+/**
+ * An event to be sent by the NotificationStackScrollLayout to the NotificationsPlaceholder, when
+ * TalkBack runs out of visible notifications, and wants to scroll the shade to access more.
+ */
+enum class AccessibilityScrollEvent {
+    SCROLL_UP,
+    SCROLL_DOWN,
+}
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/shared/model/ShadeScrollState.kt b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/shared/model/ShadeScrollState.kt
new file mode 100644
index 000000000000..3963286094f8
--- /dev/null
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/shared/model/ShadeScrollState.kt
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2024 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.statusbar.notification.stack.shared.model
+
+data class ShadeScrollState(
+    /**
+     * Whether the notification stack is scrolled to the top (i.e. when freshly opened). It also
+     * returns true, when scrolling is not possible because all the content fits in the current
+     * viewport.
+     */
+    val isScrolledToTop: Boolean = true,
+
+    /**
+     * Current scroll position of the shade. 0 when scrolled to the top, [maxScrollPosition] when
+     * scrolled all the way to the bottom.
+     */
+    val scrollPosition: Int = 0,
+
+    /**
+     * Max scroll position of the shade. 0, when no scrolling is possible e.g. all the content fits
+     * in the current viewport.
+     */
+    val maxScrollPosition: Int = 0,
+)
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/view/NotificationScrollView.kt b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/view/NotificationScrollView.kt
index 6ad9f01ca4ff..5249a6d304ec 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/view/NotificationScrollView.kt
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/view/NotificationScrollView.kt
@@ -17,7 +17,9 @@
 package com.android.systemui.statusbar.notification.stack.ui.view
 
 import android.view.View
+import com.android.systemui.statusbar.notification.stack.shared.model.AccessibilityScrollEvent
 import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrimShape
+import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrollState
 import java.util.function.Consumer
 
 /**
@@ -35,6 +37,9 @@ interface NotificationScrollView {
     /** Height in pixels required to display the top HeadsUp Notification. */
     val topHeadsUpHeight: Int
 
+    /** Bottom inset of the Notification Stack that us used to display the Shelf. */
+    val stackBottomInset: Int
+
     /**
      * Since this is an interface rather than a literal View, this provides cast-like access to the
      * underlying view.
@@ -62,12 +67,15 @@ interface NotificationScrollView {
     /** set the bottom-most y position in px, where we can draw HUNs in this view's coordinates */
     fun setHeadsUpBottom(headsUpBottom: Float)
 
-    /** set whether the view has been scrolled all the way to the top */
-    fun setScrolledToTop(scrolledToTop: Boolean)
+    /** Updates the current scroll state of the notification shade. */
+    fun setScrollState(scrollState: ShadeScrollState)
 
     /** Set a consumer for synthetic scroll events */
     fun setSyntheticScrollConsumer(consumer: Consumer<Float>?)
 
+    /** Set a consumer for accessibility actions to be handled by the placeholder. */
+    fun setAccessibilityScrollEventConsumer(consumer: Consumer<AccessibilityScrollEvent>?)
+
     /** Set a consumer for current gesture overscroll events */
     fun setCurrentGestureOverscrollConsumer(consumer: Consumer<Boolean>?)
 
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/viewbinder/NotificationScrollViewBinder.kt b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/viewbinder/NotificationScrollViewBinder.kt
index fb42ee7908b2..4a768714b84f 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/viewbinder/NotificationScrollViewBinder.kt
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/viewbinder/NotificationScrollViewBinder.kt
@@ -83,9 +83,11 @@ constructor(
             }
 
             launch { viewModel.maxAlpha.collectTraced { view.setMaxAlpha(it) } }
-            launch { viewModel.scrolledToTop.collectTraced { view.setScrolledToTop(it) } }
+            launch { viewModel.shadeScrollState.collect { view.setScrollState(it) } }
             launch {
-                viewModel.expandFraction.collectTraced { view.setExpandFraction(it.coerceIn(0f, 1f)) }
+                viewModel.expandFraction.collectTraced {
+                    view.setExpandFraction(it.coerceIn(0f, 1f))
+                }
             }
             launch { viewModel.qsExpandFraction.collectTraced { view.setQsExpandFraction(it) } }
             launch {
@@ -94,7 +96,9 @@ constructor(
                 }
             }
             launch {
-                viewModel.alphaForLockscreenFadeIn.collectTraced { view.setAlphaForLockscreenFadeIn(it) }
+                viewModel.alphaForLockscreenFadeIn.collectTraced {
+                    view.setAlphaForLockscreenFadeIn(it)
+                }
             }
             launch { viewModel.isScrollable.collectTraced { view.setScrollingEnabled(it) } }
             launch { viewModel.isDozing.collectTraced { isDozing -> view.setDozing(isDozing) } }
@@ -109,9 +113,13 @@ constructor(
                     .collectTraced { view.setStackTop(-(view.getHeadsUpInset().toFloat())) }
             }
             launch {
-                viewModel.shouldCloseGuts.filter { it }.collectTraced { view.closeGutsOnSceneTouch() }
+                viewModel.shouldCloseGuts
+                    .filter { it }
+                    .collectTraced { view.closeGutsOnSceneTouch() }
+            }
+            launch {
+                viewModel.suppressHeightUpdates.collectTraced { view.suppressHeightUpdates(it) }
             }
-            launch { viewModel.suppressHeightUpdates.collectTraced { view.suppressHeightUpdates(it) } }
 
             launchAndDispose {
                 view.setSyntheticScrollConsumer(viewModel.syntheticScrollConsumer)
@@ -120,11 +128,13 @@ constructor(
                 view.setRemoteInputRowBottomBoundConsumer(
                     viewModel.remoteInputRowBottomBoundConsumer
                 )
+                view.setAccessibilityScrollEventConsumer(viewModel.accessibilityScrollEventConsumer)
                 DisposableHandle {
                     view.setSyntheticScrollConsumer(null)
                     view.setCurrentGestureOverscrollConsumer(null)
                     view.setCurrentGestureInGutsConsumer(null)
                     view.setRemoteInputRowBottomBoundConsumer(null)
+                    view.setAccessibilityScrollEventConsumer(null)
                 }
             }
         }
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/viewmodel/NotificationScrollViewModel.kt b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/viewmodel/NotificationScrollViewModel.kt
index aec81b0241a2..574ca3ffe5b6 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/viewmodel/NotificationScrollViewModel.kt
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/viewmodel/NotificationScrollViewModel.kt
@@ -34,8 +34,10 @@ import com.android.systemui.shade.domain.interactor.ShadeInteractor
 import com.android.systemui.shade.shared.model.ShadeMode
 import com.android.systemui.statusbar.domain.interactor.RemoteInputInteractor
 import com.android.systemui.statusbar.notification.stack.domain.interactor.NotificationStackAppearanceInteractor
+import com.android.systemui.statusbar.notification.stack.shared.model.AccessibilityScrollEvent
 import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrimClipping
 import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrimShape
+import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrollState
 import com.android.systemui.statusbar.notification.stack.ui.viewmodel.NotificationTransitionThresholds.EXPANSION_FOR_DELAYED_STACK_FADE_IN
 import com.android.systemui.statusbar.notification.stack.ui.viewmodel.NotificationTransitionThresholds.EXPANSION_FOR_MAX_SCRIM_ALPHA
 import com.android.systemui.util.kotlin.ActivatableFlowDumper
@@ -255,16 +257,16 @@ constructor(
     val maxAlpha: Flow<Float> =
         stackAppearanceInteractor.alphaForBrightnessMirror.dumpValue("maxAlpha")
 
-    /**
-     * Whether the notification stack is scrolled to the top; i.e., it cannot be scrolled down any
-     * further.
-     */
-    val scrolledToTop: Flow<Boolean> =
-        stackAppearanceInteractor.scrolledToTop.dumpValue("scrolledToTop")
+    /** Scroll state of the notification shade. */
+    val shadeScrollState: Flow<ShadeScrollState> = stackAppearanceInteractor.shadeScrollState
 
     /** Receives the amount (px) that the stack should scroll due to internal expansion. */
     val syntheticScrollConsumer: (Float) -> Unit = stackAppearanceInteractor::setSyntheticScroll
 
+    /** Receives an event to scroll the stack up or down. */
+    val accessibilityScrollEventConsumer: (AccessibilityScrollEvent) -> Unit =
+        stackAppearanceInteractor::sendAccessibilityScrollEvent
+
     /**
      * Receives whether the current touch gesture is overscroll as it has already been consumed by
      * the stack.
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/viewmodel/NotificationsPlaceholderViewModel.kt b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/viewmodel/NotificationsPlaceholderViewModel.kt
index c8e83581e831..a8ce47cf2dd3 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/viewmodel/NotificationsPlaceholderViewModel.kt
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/notification/stack/ui/viewmodel/NotificationsPlaceholderViewModel.kt
@@ -27,12 +27,15 @@ import com.android.systemui.shade.domain.interactor.ShadeInteractor
 import com.android.systemui.statusbar.domain.interactor.RemoteInputInteractor
 import com.android.systemui.statusbar.notification.domain.interactor.HeadsUpNotificationInteractor
 import com.android.systemui.statusbar.notification.stack.domain.interactor.NotificationStackAppearanceInteractor
+import com.android.systemui.statusbar.notification.stack.shared.model.AccessibilityScrollEvent
 import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrimBounds
 import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrimRounding
+import com.android.systemui.statusbar.notification.stack.shared.model.ShadeScrollState
 import com.android.systemui.util.kotlin.ActivatableFlowDumper
 import com.android.systemui.util.kotlin.ActivatableFlowDumperImpl
 import dagger.assisted.AssistedFactory
 import dagger.assisted.AssistedInject
+import java.util.function.Consumer
 import kotlinx.coroutines.coroutineScope
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.filter
@@ -140,9 +143,9 @@ constructor(
     /** The bottom bound of the currently focused remote input notification row. */
     val remoteInputRowBottomBound = remoteInputInteractor.remoteInputRowBottomBound
 
-    /** Sets whether the notification stack is scrolled to the top. */
-    fun setScrolledToTop(scrolledToTop: Boolean) {
-        interactor.setScrolledToTop(scrolledToTop)
+    /** Updates the current scroll state of the notification shade. */
+    fun setScrollState(scrollState: ShadeScrollState) {
+        interactor.setScrollState(scrollState)
     }
 
     /** Sets whether the heads up notification is animating away. */
@@ -155,6 +158,11 @@ constructor(
         headsUpNotificationInteractor.snooze()
     }
 
+    /** Set a consumer for accessibility events to be handled by the placeholder. */
+    fun setAccessibilityScrollEventConsumer(consumer: Consumer<AccessibilityScrollEvent>?) {
+        interactor.setAccessibilityScrollEventConsumer(consumer)
+    }
+
     @AssistedFactory
     interface Factory {
         fun create(): NotificationsPlaceholderViewModel