1/*
2 * Copyright (C) 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.server;
18
19import android.os.Handler;
20import android.os.Trace;
21
22/**
23 * Shared singleton foreground thread for the system.  This is a thread for
24 * operations that affect what's on the display, which needs to have a minimum
25 * of latency.  This thread should pretty much only be used by the WindowManager,
26 * DisplayManager, and InputManager to perform quick operations in real time.
27 */
28public final class DisplayThread extends ServiceThread {
29    private static DisplayThread sInstance;
30    private static Handler sHandler;
31
32    private DisplayThread() {
33        super("android.display", android.os.Process.THREAD_PRIORITY_DISPLAY, false /*allowIo*/);
34    }
35
36    private static void ensureThreadLocked() {
37        if (sInstance == null) {
38            sInstance = new DisplayThread();
39            sInstance.start();
40            sInstance.getLooper().setTraceTag(Trace.TRACE_TAG_ACTIVITY_MANAGER);
41            sHandler = new Handler(sInstance.getLooper());
42        }
43    }
44
45    public static DisplayThread get() {
46        synchronized (DisplayThread.class) {
47            ensureThreadLocked();
48            return sInstance;
49        }
50    }
51
52    public static Handler getHandler() {
53        synchronized (DisplayThread.class) {
54            ensureThreadLocked();
55            return sHandler;
56        }
57    }
58}
59