Support the ability to force-show navigation for GKS

GKS requested to force show nav bar except for Launcher apps.

Returns null in InsetsPolicy.getNavControlTarget() to forcibly
show the nav bar when:
  - The feature is enabled.
  - The activity type of the focus window is ACTIVITY_TYPE_STANDARD.

Bug: 161689887
Test: manual:
      1. adb shell settings put secure "nav_bar_kids_mode" "1"
      2. choose 3-buttons navigation mode in
         Settings>System>Gestures>System navigation
      2. open an app that hides nav bar and check if the nav bar is
         still visible.
Change-Id: I7679da7d8b0892317d04cdc3553fe9a8fcdb2292

core/java/com/android/internal/policy/ForceShowNavigationBarSettingsObserver.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright (C) 2022 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.internal.policy;
+
+import android.content.ContentResolver;
+import android.content.Context;
+import android.database.ContentObserver;
+import android.os.Handler;
+import android.os.UserHandle;
+import android.provider.Settings;
+
+/**
+ * A ContentObserver for listening force show navigation bar relative setting keys:
+ *  - {@link Settings.Secure#NAVIGATION_MODE}
+ *  - {@link Settings.Secure#NAV_BAR_KIDS_MODE}
+ *
+ * @hide
+ */
+public class ForceShowNavigationBarSettingsObserver extends ContentObserver {
+    private Context mContext;
+    private Runnable mOnChangeRunnable;
+
+    public ForceShowNavigationBarSettingsObserver(Handler handler, Context context) {
+        super(handler);
+        mContext = context;
+    }
+
+    public void setOnChangeRunnable(Runnable r) {
+        mOnChangeRunnable = r;
+    }
+
+    /**
+     * Registers the observer.
+     */
+    public void register() {
+        final ContentResolver r = mContext.getContentResolver();
+        r.registerContentObserver(
+                Settings.Secure.getUriFor(Settings.Secure.NAVIGATION_MODE),
+                false, this, UserHandle.USER_ALL);
+        r.registerContentObserver(
+                Settings.Secure.getUriFor(Settings.Secure.NAV_BAR_KIDS_MODE),
+                false, this, UserHandle.USER_ALL);
+    }
+
+    /**
+     * Unregisters the observer.
+     */
+    public void unregister() {
+        mContext.getContentResolver().unregisterContentObserver(this);
+    }
+
+    @Override
+    public void onChange(boolean selfChange) {
+        if (mOnChangeRunnable != null) {
+            mOnChangeRunnable.run();
+        }
+    }
+
+    /**
+     * Returns true only when it's in three button nav mode and the kid nav bar mode is enabled.
+     * Otherwise, return false.
+     */
+    public boolean isEnabled() {
+        return Settings.Secure.getIntForUser(mContext.getContentResolver(),
+                Settings.Secure.NAVIGATION_MODE, 0, UserHandle.USER_CURRENT) == 0
+                && Settings.Secure.getIntForUser(mContext.getContentResolver(),
+                Settings.Secure.NAV_BAR_KIDS_MODE, 0, UserHandle.USER_CURRENT) == 1;
+    }
+}

services/core/java/com/android/server/wm/DisplayPolicy.java

@@ -139,6 +139,7 @@ import android.view.accessibility.AccessibilityManager;
 
 import com.android.internal.R;
 import com.android.internal.annotations.VisibleForTesting;
+import com.android.internal.policy.ForceShowNavigationBarSettingsObserver;
 import com.android.internal.policy.GestureNavigationSettingsObserver;
 import com.android.internal.policy.ScreenDecorationsUtils;
 import com.android.internal.policy.SystemBarUtils;
@@ -381,6 +382,9 @@ public class DisplayPolicy {
 
     private final WindowManagerInternal.AppTransitionListener mAppTransitionListener;
 
+    private final ForceShowNavigationBarSettingsObserver mForceShowNavigationBarSettingsObserver;
+    private boolean mForceShowNavigationBarEnabled;
+
     private class PolicyHandler extends Handler {
 
         PolicyHandler(Looper looper) {
@@ -652,6 +656,18 @@ public class DisplayPolicy {
             }
         });
         mHandler.post(mGestureNavigationSettingsObserver::register);
+
+        mForceShowNavigationBarSettingsObserver = new ForceShowNavigationBarSettingsObserver(
+                mHandler, mContext);
+        mForceShowNavigationBarSettingsObserver.setOnChangeRunnable(() -> {
+            synchronized (mLock) {
+                mForceShowNavigationBarEnabled =
+                        mForceShowNavigationBarSettingsObserver.isEnabled();
+                updateSystemBarAttributes();
+            }
+        });
+        mForceShowNavigationBarEnabled = mForceShowNavigationBarSettingsObserver.isEnabled();
+        mHandler.post(mForceShowNavigationBarSettingsObserver::register);
     }
 
     /**
@@ -791,6 +807,10 @@ public class DisplayPolicy {
         return mWindowManagerDrawComplete;
     }
 
+    public boolean isForceShowNavigationBarEnabled() {
+        return mForceShowNavigationBarEnabled;
+    }
+
     public ScreenOnListener getScreenOnListener() {
         return mScreenOnListener;
     }
@@ -2755,6 +2775,8 @@ public class DisplayPolicy {
         }
         pw.print(prefix); pw.print("mTopIsFullscreen="); pw.println(mTopIsFullscreen);
         pw.print(prefix); pw.print("mForceStatusBar="); pw.print(mForceStatusBar);
+        pw.print(prefix); pw.print("mForceShowNavigationBarEnabled=");
+        pw.print(mForceShowNavigationBarEnabled);
         pw.print(" mAllowLockscreenWhenOn="); pw.println(mAllowLockscreenWhenOn);
         pw.print(prefix); pw.print("mRemoteInsetsControllerControlsSystemBars=");
         pw.println(mDisplayContent.getInsetsPolicy().getRemoteInsetsControllerControlsSystemBars());
@@ -2832,6 +2854,7 @@ public class DisplayPolicy {
     void release() {
         mDisplayContent.mTransitionController.unregisterLegacyListener(mAppTransitionListener);
         mHandler.post(mGestureNavigationSettingsObserver::unregister);
+        mHandler.post(mForceShowNavigationBarSettingsObserver::unregister);
         mImmersiveModeConfirmation.release();
     }
 

services/core/java/com/android/server/wm/InsetsPolicy.java

@@ -18,6 +18,7 @@ package com.android.server.wm;
 
 import static android.app.StatusBarManager.WINDOW_STATE_HIDDEN;
 import static android.app.StatusBarManager.WINDOW_STATE_SHOWING;
+import static android.app.WindowConfiguration.ACTIVITY_TYPE_STANDARD;
 import static android.view.InsetsController.ANIMATION_TYPE_HIDE;
 import static android.view.InsetsController.ANIMATION_TYPE_SHOW;
 import static android.view.InsetsController.LAYOUT_INSETS_DURING_ANIMATION_HIDDEN;
@@ -424,6 +425,14 @@ class InsetsPolicy {
             // Notification shade has control anyways, no reason to force anything.
             return focusedWin;
         }
+        if (mPolicy.isForceShowNavigationBarEnabled()
+                && focusedWin.getActivityType() == ACTIVITY_TYPE_STANDARD) {
+            // When "force show navigation bar" is enabled, it means we are in kid navigation bar
+            // and 3-button navigation bar mode. In this mode, the navigation bar is forcibly shown
+            // when activity type is ACTIVITY_TYPE_STANDARD which means Launcher or Recent could
+            // still control the navigation bar in this mode.
+            return null;
+        }
         if (remoteInsetsControllerControlsSystemBars(focusedWin)) {
             mDisplayContent.mRemoteInsetsControlTarget.topFocusedWindowChanged(
                     focusedWin.mAttrs.packageName);