xref: /frameworks/base/core/java/android/provider/FontsContract.java

/*
 * Copyright (C) 2017 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 android.provider;

import android.app.ActivityThread;
import android.content.ContentResolver;
import android.content.ContentUris;
import android.content.Context;
import android.content.pm.PackageManager;
import android.content.pm.ProviderInfo;
import android.database.Cursor;
import android.graphics.fonts.FontRequest;
import android.graphics.fonts.FontResult;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.ParcelFileDescriptor;
import android.os.Process;
import android.os.ResultReceiver;
import android.util.Log;

import com.android.internal.annotations.GuardedBy;

import java.io.FileNotFoundException;
import java.util.ArrayList;

/**
 * Utility class to deal with Font ContentProviders.
 */
public class FontsContract {
    private static final String TAG = "FontsContract";

    /**
     * Defines the constants used in a response from a Font Provider. The cursor returned from the
     * query should have the ID column populated with the content uri ID for the resulting font.
     * This should point to a real file or shared memory, as the client will mmap the given file
     * descriptor. Pipes, sockets and other non-mmap-able file descriptors will fail to load in the
     * client application.
     */
    public static final class Columns implements BaseColumns {
        /**
         * Constant used to request data from a font provider. The cursor returned from the query
         * should have this column populated with an int for the ttc index for the resulting font.
         */
        public static final String TTC_INDEX = "font_ttc_index";
        /**
         * Constant used to request data from a font provider. The cursor returned from the query
         * may populate this column with the font variation settings String information for the
         * font.
         */
        public static final String VARIATION_SETTINGS = "font_variation_settings";
        /**
         * Constant used to request data from a font provider. The cursor returned from the query
         * should have this column populated with the int style for the resulting font. This should
         * be one of {@link android.graphics.Typeface#NORMAL},
         * {@link android.graphics.Typeface#BOLD}, {@link android.graphics.Typeface#ITALIC} or
         * {@link android.graphics.Typeface#BOLD_ITALIC}
         */
        public static final String STYLE = "font_style";
    }

    /**
     * Constant used to identify the List of {@link ParcelFileDescriptor} item in the Bundle
     * returned to the ResultReceiver in getFont.
     * @hide
     */
    public static final String PARCEL_FONT_RESULTS = "font_results";

    /** @hide */
    public static final int RESULT_CODE_OK = 0;
    /** @hide */
    public static final int RESULT_CODE_FONT_NOT_FOUND = 1;
    /** @hide */
    public static final int RESULT_CODE_PROVIDER_NOT_FOUND = 2;

    private static final int THREAD_RENEWAL_THRESHOLD_MS = 10000;

    private final Context mContext;
    private final PackageManager mPackageManager;
    private final Object mLock = new Object();
    @GuardedBy("mLock")
    private Handler mHandler;
    @GuardedBy("mLock")
    private HandlerThread mThread;

    /** @hide */
    public FontsContract() {
        // TODO: investigate if the system context is the best option here. ApplicationContext or
        // the one passed by developer?
        // TODO: Looks like ActivityThread.currentActivityThread() can return null. Check when it
        // returns null and check if we need to handle null case.
        mContext = ActivityThread.currentActivityThread().getSystemContext();
        mPackageManager = mContext.getPackageManager();
    }

    // We use a background thread to post the content resolving work for all requests on. This
    // thread should be quit/stopped after all requests are done.
    private final Runnable mReplaceDispatcherThreadRunnable = new Runnable() {
        @Override
        public void run() {
            synchronized (mLock) {
                if (mThread != null) {
                    mThread.quitSafely();
                    mThread = null;
                    mHandler = null;
                }
            }
        }
    };

    /**
     * @hide
     */
    public void getFont(FontRequest request, ResultReceiver receiver) {
        synchronized (mLock) {
            if (mHandler == null) {
                mThread = new HandlerThread("fonts", Process.THREAD_PRIORITY_BACKGROUND);
                mThread.start();
                mHandler = new Handler(mThread.getLooper());
            }
            mHandler.post(() -> {
                String providerAuthority = request.getProviderAuthority();
                // TODO: Implement cert checking for non-system apps
                ProviderInfo providerInfo = mPackageManager.resolveContentProvider(
                        providerAuthority, PackageManager.MATCH_SYSTEM_ONLY);
                if (providerInfo == null) {
                    receiver.send(RESULT_CODE_PROVIDER_NOT_FOUND, null);
                    return;
                }
                Bundle result = getFontFromProvider(request, receiver, providerInfo);
                if (result == null) {
                    receiver.send(RESULT_CODE_FONT_NOT_FOUND, null);
                    return;
                }
                receiver.send(RESULT_CODE_OK, result);
            });
            mHandler.removeCallbacks(mReplaceDispatcherThreadRunnable);
            mHandler.postDelayed(mReplaceDispatcherThreadRunnable, THREAD_RENEWAL_THRESHOLD_MS);
        }
    }

    private Bundle getFontFromProvider(FontRequest request, ResultReceiver receiver,
            ProviderInfo providerInfo) {
        ArrayList<FontResult> result = null;
        Uri uri = new Uri.Builder().scheme(ContentResolver.SCHEME_CONTENT)
                .authority(providerInfo.authority)
                .build();
        try (Cursor cursor = mContext.getContentResolver().query(uri, new String[] { Columns._ID,
                        Columns.TTC_INDEX, Columns.VARIATION_SETTINGS, Columns.STYLE },
                "query = ?", new String[] { request.getQuery() }, null);) {
            // TODO: Should we restrict the amount of fonts that can be returned?
            // TODO: Write documentation explaining that all results should be from the same family.
            if (cursor != null && cursor.getCount() > 0) {
                result = new ArrayList<>();
                final int idColumnIndex = cursor.getColumnIndex(Columns._ID);
                final int ttcIndexColumnIndex = cursor.getColumnIndex(Columns.TTC_INDEX);
                final int vsColumnIndex = cursor.getColumnIndex(Columns.VARIATION_SETTINGS);
                final int styleColumnIndex = cursor.getColumnIndex(Columns.STYLE);
                while (cursor.moveToNext()) {
                    long id = cursor.getLong(idColumnIndex);
                    Uri fileUri = ContentUris.withAppendedId(uri, id);
                    try {
                        ParcelFileDescriptor pfd =
                                mContext.getContentResolver().openFileDescriptor(fileUri, "r");
                        final int ttcIndex = cursor.getInt(ttcIndexColumnIndex);
                        final String variationSettings = cursor.getString(vsColumnIndex);
                        final int style = cursor.getInt(styleColumnIndex);
                        result.add(new FontResult(pfd, ttcIndex, variationSettings, style));
                    } catch (FileNotFoundException e) {
                        Log.e(TAG, "FileNotFoundException raised when interacting with content "
                                + "provider " + providerInfo.authority, e);
                    }
                }
            }
        }
        if (result != null && !result.isEmpty()) {
            Bundle bundle = new Bundle();
            bundle.putParcelableArrayList(PARCEL_FONT_RESULTS, result);
            return bundle;
        }
        return null;
    }
}