lawnchair/res/drawable/rounded_action_button.xml

<?xml version="1.0" encoding="utf-8"?><!--
  ~ 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, soft]ware
  ~ distributed under the License is distributed on an "AS IS" BASIS,
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  ~ See the License for the specific language governing permissions and
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  -->


<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <solid android:color="@color/materialColorSurfaceContainerLow" />
    <corners android:radius="@dimen/rounded_button_radius" />
    <stroke
        android:width="1dp"
        android:color="@color/materialColorSurfaceContainerLow" />
</shape>