com/android/wm/shell/common/DisplayChangeController.java

/*
 * Copyright (C) 2019 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.wm.shell.common;

import android.os.RemoteException;
import android.view.IDisplayWindowRotationCallback;
import android.view.IDisplayWindowRotationController;
import android.view.IWindowManager;
import android.window.WindowContainerTransaction;

import androidx.annotation.BinderThread;

import com.android.wm.shell.common.annotations.ShellMainThread;

import java.util.ArrayList;

/**
 * This module deals with display rotations coming from WM. When WM starts a rotation: after it has
 * frozen the screen, it will call into this class. This will then call all registered local
 * controllers and give them a chance to queue up task changes to be applied synchronously with that
 * rotation.
 */
public class DisplayChangeController {

    private final ShellExecutor mMainExecutor;
    private final IWindowManager mWmService;
    private final IDisplayWindowRotationController mControllerImpl;

    private final ArrayList<OnDisplayChangingListener> mRotationListener =
            new ArrayList<>();
    private final ArrayList<OnDisplayChangingListener> mTmpListeners = new ArrayList<>();

    public DisplayChangeController(IWindowManager wmService, ShellExecutor mainExecutor) {
        mMainExecutor = mainExecutor;
        mWmService = wmService;
        mControllerImpl = new DisplayWindowRotationControllerImpl();
        try {
            mWmService.setDisplayWindowRotationController(mControllerImpl);
        } catch (RemoteException e) {
            throw new RuntimeException("Unable to register rotation controller");
        }
    }

    /**
     * Adds a display rotation controller.
     */
    public void addRotationListener(OnDisplayChangingListener listener) {
        synchronized (mRotationListener) {
            mRotationListener.add(listener);
        }
    }

    /**
     * Removes a display rotation controller.
     */
    public void removeRotationListener(OnDisplayChangingListener listener) {
        synchronized (mRotationListener) {
            mRotationListener.remove(listener);
        }
    }

    private void onRotateDisplay(int displayId, final int fromRotation, final int toRotation,
            IDisplayWindowRotationCallback callback) {
        WindowContainerTransaction t = new WindowContainerTransaction();
        synchronized (mRotationListener) {
            mTmpListeners.clear();
            // Make a local copy in case the handlers add/remove themselves.
            mTmpListeners.addAll(mRotationListener);
        }
        for (OnDisplayChangingListener c : mTmpListeners) {
            c.onRotateDisplay(displayId, fromRotation, toRotation, t);
        }
        try {
            callback.continueRotateDisplay(toRotation, t);
        } catch (RemoteException e) {
        }
    }

    @BinderThread
    private class DisplayWindowRotationControllerImpl
            extends IDisplayWindowRotationController.Stub {
        @Override
        public void onRotateDisplay(int displayId, final int fromRotation,
                final int toRotation, IDisplayWindowRotationCallback callback) {
            mMainExecutor.execute(() -> {
                DisplayChangeController.this.onRotateDisplay(displayId, fromRotation, toRotation,
                        callback);
            });
        }
    }

    /**
     * Give a listener a chance to queue up configuration changes to execute as part of a
     * display rotation. The contents of {@link #onRotateDisplay} must run synchronously.
     */
    @ShellMainThread
    public interface OnDisplayChangingListener {
        /**
         * Called before the display is rotated. Contents of this method must run synchronously.
         * @param displayId Id of display that is rotating.
         * @param fromRotation starting rotation of the display.
         * @param toRotation target rotation of the display (after rotating).
         * @param t A task transaction to populate.
         */
        void onRotateDisplay(int displayId, int fromRotation, int toRotation,
                WindowContainerTransaction t);
    }
}