content: /*
   * Copyright (C) 2013 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.server;
  
  import android.os.Handler;
  import android.os.Process;
  import android.os.Trace;
  
  /**
   * Shared singleton foreground thread for the system.  This is a thread for
   * operations that affect what's on the display, which needs to have a minimum
   * of latency.  This thread should pretty much only be used by the WindowManager,
   * DisplayManager, and InputManager to perform quick operations in real time.
   */
  public final class DisplayThread extends ServiceThread {
      private static DisplayThread sInstance;
      private static Handler sHandler;
  
      private DisplayThread() {
          // DisplayThread runs important stuff, but these are not as important as things running in
          // AnimationThread. Thus, set the priority to one lower.
          super("android.display", Process.THREAD_PRIORITY_DISPLAY + 1, false /*allowIo*/);
      }
  
      private static void ensureThreadLocked() {
          if (sInstance == null) {
              sInstance = new DisplayThread();
              sInstance.start();
              sInstance.getLooper().setTraceTag(Trace.TRACE_TAG_SYSTEM_SERVER);
              sHandler = new Handler(sInstance.getLooper());
          }
      }
  
      public static DisplayThread get() {
          synchronized (DisplayThread.class) {
              ensureThreadLocked();
              return sInstance;
          }
      }
  
      public static Handler getHandler() {
          synchronized (DisplayThread.class) {
              ensureThreadLocked();
              return sHandler;
          }
      }
  }
  