diff --git a/res/layout/app_widget_resize_frame.xml b/res/layout/app_widget_resize_frame.xml
index 2e476df..671dbc6 100644
--- a/res/layout/app_widget_resize_frame.xml
+++ b/res/layout/app_widget_resize_frame.xml
@@ -26,6 +26,7 @@
 
         <!-- Frame -->
         <ImageView
+            android:id="@+id/widget_resize_frame"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
             android:layout_gravity="center"
diff --git a/res/values/dimens.xml b/res/values/dimens.xml
index 8d160c4..cf830c7 100644
--- a/res/values/dimens.xml
+++ b/res/values/dimens.xml
@@ -283,4 +283,7 @@
 <!-- Taskbar related (placeholders to compile in Launcher3 without Quickstep) -->
     <dimen name="taskbar_size">0dp</dimen>
 
+    <!-- Size of the maximum radius for the enforced rounded rectangles. -->
+    <dimen name="enforced_rounded_corner_max_radius">16dp</dimen>
+
 </resources>
diff --git a/src/com/android/launcher3/AppWidgetResizeFrame.java b/src/com/android/launcher3/AppWidgetResizeFrame.java
index d02efb0..ab91785 100644
--- a/src/com/android/launcher3/AppWidgetResizeFrame.java
+++ b/src/com/android/launcher3/AppWidgetResizeFrame.java
@@ -14,12 +14,15 @@
 import android.content.Context;
 import android.graphics.Point;
 import android.graphics.Rect;
+import android.graphics.drawable.Drawable;
+import android.graphics.drawable.GradientDrawable;
 import android.os.Bundle;
 import android.util.AttributeSet;
 import android.util.SizeF;
 import android.view.KeyEvent;
 import android.view.MotionEvent;
 import android.view.View;
+import android.widget.ImageView;
 
 import androidx.annotation.Nullable;
 
@@ -166,6 +169,15 @@
         DragLayer dl = launcher.getDragLayer();
         AppWidgetResizeFrame frame = (AppWidgetResizeFrame) launcher.getLayoutInflater()
                 .inflate(R.layout.app_widget_resize_frame, dl, false);
+        if (widget.hasEnforcedCornerRadius()) {
+            float enforcedCornerRadius = widget.getEnforcedCornerRadius();
+            ImageView imageView = frame.findViewById(R.id.widget_resize_frame);
+            Drawable d = imageView.getDrawable();
+            if (d instanceof GradientDrawable) {
+                GradientDrawable gd = (GradientDrawable) d.mutate();
+                gd.setCornerRadius(enforcedCornerRadius);
+            }
+        }
         frame.setupForWidget(widget, cellLayout, dl);
         ((DragLayer.LayoutParams) frame.getLayoutParams()).customPosition = true;
 
diff --git a/src/com/android/launcher3/config/FeatureFlags.java b/src/com/android/launcher3/config/FeatureFlags.java
index 96251f0..7f76d27 100644
--- a/src/com/android/launcher3/config/FeatureFlags.java
+++ b/src/com/android/launcher3/config/FeatureFlags.java
@@ -215,6 +215,9 @@
     public static final BooleanFlag ENABLE_SPLIT_SELECT = getDebugFlag(
             "ENABLE_SPLIT_SELECT", false, "Uses new split screen selection overview UI");
 
+    public static final BooleanFlag ENABLE_ENFORCED_ROUNDED_CORNERS = new DeviceFlag(
+            "ENABLE_ENFORCED_ROUNDED_CORNERS", true, "Enforce rounded corners on all App Widgets");
+
     public static void initialize(Context context) {
         synchronized (sDebugFlags) {
             for (DebugFlag flag : sDebugFlags) {
diff --git a/src/com/android/launcher3/dragndrop/AppWidgetHostViewDrawable.java b/src/com/android/launcher3/dragndrop/AppWidgetHostViewDrawable.java
index 92ae670..5cd95dc 100644
--- a/src/com/android/launcher3/dragndrop/AppWidgetHostViewDrawable.java
+++ b/src/com/android/launcher3/dragndrop/AppWidgetHostViewDrawable.java
@@ -17,8 +17,12 @@
 
 import android.graphics.Canvas;
 import android.graphics.ColorFilter;
+import android.graphics.Outline;
 import android.graphics.Paint;
+import android.graphics.Path;
 import android.graphics.PixelFormat;
+import android.graphics.Rect;
+import android.graphics.RectF;
 import android.graphics.drawable.Drawable;
 
 import com.android.launcher3.widget.LauncherAppWidgetHostView;
@@ -28,14 +32,30 @@
 
     private final LauncherAppWidgetHostView mAppWidgetHostView;
     private Paint mPaint = new Paint();
+    private final Path mClipPath;
 
     public AppWidgetHostViewDrawable(LauncherAppWidgetHostView appWidgetHostView) {
         mAppWidgetHostView = appWidgetHostView;
+        Path clipPath = null;
+        if (appWidgetHostView.getClipToOutline()) {
+            Outline outline = new Outline();
+            mAppWidgetHostView.getOutlineProvider().getOutline(mAppWidgetHostView, outline);
+            Rect rect = new Rect();
+            if (outline.getRect(rect)) {
+                float radius = outline.getRadius();
+                clipPath = new Path();
+                clipPath.addRoundRect(new RectF(rect), radius, radius, Path.Direction.CCW);
+            }
+        }
+        mClipPath = clipPath;
     }
 
     @Override
     public void draw(Canvas canvas) {
         int saveCount = canvas.saveLayer(0, 0, getIntrinsicWidth(), getIntrinsicHeight(), mPaint);
+        if (mClipPath != null) {
+            canvas.clipPath(mClipPath);
+        }
         mAppWidgetHostView.draw(canvas);
         canvas.restoreToCount(saveCount);
     }
diff --git a/src/com/android/launcher3/widget/LauncherAppWidgetHostView.java b/src/com/android/launcher3/widget/LauncherAppWidgetHostView.java
index 5c18faf..2e542ed 100644
--- a/src/com/android/launcher3/widget/LauncherAppWidgetHostView.java
+++ b/src/com/android/launcher3/widget/LauncherAppWidgetHostView.java
@@ -20,6 +20,7 @@
 import android.content.Context;
 import android.content.res.Configuration;
 import android.graphics.Canvas;
+import android.graphics.Outline;
 import android.graphics.Rect;
 import android.graphics.RectF;
 import android.os.Handler;
@@ -32,12 +33,14 @@
 import android.view.View;
 import android.view.ViewDebug;
 import android.view.ViewGroup;
+import android.view.ViewOutlineProvider;
 import android.view.accessibility.AccessibilityNodeInfo;
 import android.widget.AdapterView;
 import android.widget.Advanceable;
 import android.widget.RemoteViews;
 
 import androidx.annotation.Nullable;
+import androidx.annotation.UiThread;
 
 import com.android.launcher3.CheckLongPressHelper;
 import com.android.launcher3.Launcher;
@@ -95,6 +98,18 @@
     private final Rect mWidgetSizeAtDrag = new Rect();
     private final RectF mTempRectF = new RectF();
     private final boolean mIsRtl;
+    private final Rect mEnforcedRectangle = new Rect();
+    private final float mEnforcedCornerRadius;
+    private final ViewOutlineProvider mCornerRadiusEnforcementOutline = new ViewOutlineProvider() {
+        @Override
+        public void getOutline(View view, Outline outline) {
+            if (mEnforcedRectangle.isEmpty() || mEnforcedCornerRadius <= 0) {
+                outline.setEmpty();
+            } else {
+                outline.setRoundRect(mEnforcedRectangle, mEnforcedCornerRadius);
+            }
+        }
+    };
 
     public LauncherAppWidgetHostView(Context context) {
         super(context);
@@ -112,6 +127,8 @@
         mIsRtl = Utilities.isRtl(context.getResources());
         mColorExtractor = LocalColorExtractor.newInstance(getContext());
         mColorExtractor.setListener(this);
+
+        mEnforcedCornerRadius = RoundedCornerEnforcement.computeEnforcedRadius(getContext());
     }
 
     @Override
@@ -169,7 +186,7 @@
         if (viewGroup instanceof AdapterView) {
             return true;
         } else {
-            for (int i=0; i < viewGroup.getChildCount(); i++) {
+            for (int i = 0; i < viewGroup.getChildCount(); i++) {
                 View child = viewGroup.getChildAt(i);
                 if (child instanceof ViewGroup) {
                     if (checkScrollableRecursively((ViewGroup) child)) {
@@ -272,6 +289,8 @@
             int pageId = mWorkspace.getPageIndexForScreenId(info.screenId);
             updateColorExtraction(mCurrentWidgetSize, pageId);
         }
+
+        enforceRoundedCorners();
     }
 
     /** Starts the drag mode. */
@@ -469,4 +488,39 @@
         }
         return false;
     }
+
+    @UiThread
+    private void resetRoundedCorners() {
+        setOutlineProvider(ViewOutlineProvider.BACKGROUND);
+        setClipToOutline(false);
+    }
+
+    @UiThread
+    private void enforceRoundedCorners() {
+        if (mEnforcedCornerRadius <= 0 || !RoundedCornerEnforcement.isRoundedCornerEnabled(this)) {
+            resetRoundedCorners();
+            return;
+        }
+        View background = RoundedCornerEnforcement.findBackground(this);
+        if (RoundedCornerEnforcement.hasAppWidgetOptedOut(this, background)) {
+            resetRoundedCorners();
+            return;
+        }
+        RoundedCornerEnforcement.computeRoundedRectangle(this,
+                background,
+                mEnforcedRectangle);
+        setOutlineProvider(mCornerRadiusEnforcementOutline);
+        setClipToOutline(true);
+    }
+
+    /** Returns the corner radius currently enforced, in pixels. */
+    public float getEnforcedCornerRadius() {
+        return mEnforcedCornerRadius;
+    }
+
+    /** Returns true if the corner radius are enforced for this App Widget. */
+    public boolean hasEnforcedCornerRadius() {
+        return getClipToOutline();
+    }
+
 }
diff --git a/src/com/android/launcher3/widget/RoundedCornerEnforcement.java b/src/com/android/launcher3/widget/RoundedCornerEnforcement.java
new file mode 100644
index 0000000..99eccd1
--- /dev/null
+++ b/src/com/android/launcher3/widget/RoundedCornerEnforcement.java
@@ -0,0 +1,170 @@
+/*
+ * Copyright (C) 2021 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.launcher3.widget;
+
+import android.appwidget.AppWidgetHostView;
+import android.content.Context;
+import android.content.res.Resources;
+import android.graphics.Rect;
+import android.view.View;
+import android.view.ViewGroup;
+
+import androidx.annotation.IdRes;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+import com.android.launcher3.R;
+import com.android.launcher3.Utilities;
+import com.android.launcher3.config.FeatureFlags;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Utilities to compute the enforced the use of rounded corners on App Widgets.
+ */
+public class RoundedCornerEnforcement {
+    // This class is only a namespace and not meant to be instantiated.
+    private RoundedCornerEnforcement() {
+    }
+
+    /**
+     * Find the background view for a widget.
+     *
+     * @param appWidget the view containing the App Widget (typically the instance of
+     * {@link AppWidgetHostView}).
+     */
+    @Nullable
+    public static View findBackground(@NonNull View appWidget) {
+        List<View> backgrounds = findViewsWithId(appWidget, android.R.id.background);
+        if (backgrounds.size() == 1) {
+            return backgrounds.get(0);
+        }
+        // Really, the argument should contain the widget, so it cannot be the background.
+        if (appWidget instanceof ViewGroup) {
+            ViewGroup vg = (ViewGroup) appWidget;
+            if (vg.getChildCount() > 0) {
+                return findUndefinedBackground(vg.getChildAt(0));
+            }
+        }
+        return appWidget;
+    }
+
+    /**
+     * Check whether the app widget has opted out of the enforcement.
+     */
+    public static boolean hasAppWidgetOptedOut(@NonNull View appWidget, @NonNull View background) {
+        return background.getId() == android.R.id.background && background.getClipToOutline();
+    }
+
+    /** Check if the app widget is in the deny list. */
+    public static boolean isRoundedCornerEnabled(@NonNull View view) {
+        if (!Utilities.ATLEAST_S || !FeatureFlags.ENABLE_ENFORCED_ROUNDED_CORNERS.get()) {
+            return false;
+        }
+        // Here we need to test if the view's component is in the (to be created) deny list.
+        return true;
+    }
+
+    /**
+     * Computes the rounded rectangle needed for this app widget.
+     *
+     * @param appWidget View onto which the rounded rectangle will be applied.
+     * @param background Background view. This must be either {@code appWidget} or a descendant
+     *                  of {@code appWidget}.
+     * @param outRect Rectangle set to the rounded rectangle coordinates, in the reference frame
+     *                of {@code appWidget}.
+     */
+    public static void computeRoundedRectangle(@NonNull View appWidget, @NonNull View background,
+            @NonNull Rect outRect) {
+        outRect.left = 0;
+        outRect.right = background.getWidth();
+        outRect.top = 0;
+        outRect.bottom = background.getHeight();
+        while (background != appWidget) {
+            outRect.offset(background.getLeft(), background.getTop());
+            background = (View) background.getParent();
+        }
+    }
+
+    /**
+     * Computes the radius of the rounded rectangle that should be applied to a widget expanded
+     * in the given context.
+     */
+    public static float computeEnforcedRadius(@NonNull Context context) {
+        if (!Utilities.ATLEAST_S) {
+            return 0;
+        }
+        Resources res = context.getResources();
+        float systemRadius = res.getDimension(android.R.dimen.system_app_widget_background_radius);
+        float defaultRadius = res.getDimension(R.dimen.enforced_rounded_corner_max_radius);
+        return Math.min(defaultRadius, systemRadius);
+    }
+
+    private static List<View> findViewsWithId(View view, @IdRes int viewId) {
+        List<View> output = new ArrayList<>();
+        accumulateViewsWithId(view, viewId, output);
+        return output;
+    }
+
+    // Traverse views. If the predicate returns true, continue on the children, otherwise, don't.
+    private static void accumulateViewsWithId(View view, @IdRes int viewId, List<View> output) {
+        if (view.getId() == viewId) {
+            output.add(view);
+            return;
+        }
+        if (view instanceof ViewGroup) {
+            ViewGroup vg = (ViewGroup) view;
+            for (int i = 0; i < vg.getChildCount(); i++) {
+                accumulateViewsWithId(vg.getChildAt(i), viewId, output);
+            }
+        }
+    }
+
+    private static boolean isViewVisible(View view) {
+        if (view.getVisibility() != View.VISIBLE) {
+            return false;
+        }
+        return !view.willNotDraw() || view.getForeground() != null || view.getBackground() != null;
+    }
+
+    @Nullable
+    private static View findUndefinedBackground(View current) {
+        if (current.getVisibility() != View.VISIBLE) {
+            return null;
+        }
+        if (isViewVisible(current)) {
+            return current;
+        }
+        View lastVisibleView = null;
+        // Find the first view that is either not a ViewGroup, or a ViewGroup which will draw
+        // something, or a ViewGroup that contains more than one view.
+        if (current instanceof ViewGroup) {
+            ViewGroup vg = (ViewGroup) current;
+            for (int i = 0; i < vg.getChildCount(); i++) {
+                View visibleView = findUndefinedBackground(vg.getChildAt(i));
+                if (visibleView != null) {
+                    if (lastVisibleView != null) {
+                        return current; // At least two visible children
+                    }
+                    lastVisibleView = visibleView;
+                }
+            }
+        }
+        return lastVisibleView;
+    }
+}