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      1 /*
      2  * Copyright (C) 2017 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 
     17 package com.android.internal.view;
     18 
     19 import android.os.Handler;
     20 import android.os.Message;
     21 import android.view.Choreographer;
     22 import android.view.Display;
     23 
     24 /**
     25  * Utility class to schedule things at vsync-sf instead of vsync-app
     26  * @hide
     27  */
     28 public class SurfaceFlingerVsyncChoreographer {
     29 
     30     private static final long ONE_MS_IN_NS = 1000000;
     31     private static final long ONE_S_IN_NS = ONE_MS_IN_NS * 1000;
     32 
     33     private final Handler mHandler;
     34     private final Choreographer mChoreographer;
     35 
     36     /**
     37      * The offset between vsync-app and vsync-surfaceflinger. See
     38      * {@link #calculateAppSurfaceFlingerVsyncOffsetMs} why this is necessary.
     39      */
     40     private long mSurfaceFlingerOffsetMs;
     41 
     42     public SurfaceFlingerVsyncChoreographer(Handler handler, Display display,
     43             Choreographer choreographer) {
     44         mHandler = handler;
     45         mChoreographer = choreographer;
     46         mSurfaceFlingerOffsetMs = calculateAppSurfaceFlingerVsyncOffsetMs(display);
     47     }
     48 
     49     public long getSurfaceFlingerOffsetMs() {
     50         return mSurfaceFlingerOffsetMs;
     51     }
     52 
     53     /**
     54      * This method calculates the offset between vsync-surfaceflinger and vsync-app. If vsync-app
     55      * is a couple of milliseconds before vsync-sf, a touch or animation event that causes a surface
     56      * flinger transaction are sometimes processed before the vsync-sf tick, and sometimes after,
     57      * which leads to jank. Figure out this difference here and then post all the touch/animation
     58      * events to start being processed at vsync-sf.
     59      *
     60      * @return The offset between vsync-app and vsync-sf, or 0 if vsync app happens after vsync-sf.
     61      */
     62     private long calculateAppSurfaceFlingerVsyncOffsetMs(Display display) {
     63 
     64         // Calculate vsync offset from SurfaceFlinger.
     65         // See frameworks/native/services/surfaceflinger/SurfaceFlinger.cpp:getDisplayConfigs
     66         long vsyncPeriod = (long) (ONE_S_IN_NS / display.getRefreshRate());
     67         long sfVsyncOffset = vsyncPeriod - (display.getPresentationDeadlineNanos() - ONE_MS_IN_NS);
     68         return Math.max(0, (sfVsyncOffset - display.getAppVsyncOffsetNanos()) / ONE_MS_IN_NS);
     69     }
     70 
     71     public void scheduleAtSfVsync(Runnable r) {
     72         final long delay = calculateDelay();
     73         if (delay <= 0) {
     74             r.run();
     75         } else {
     76             mHandler.postDelayed(r, delay);
     77         }
     78     }
     79 
     80     public void scheduleAtSfVsync(Handler h, Message m) {
     81         final long delay = calculateDelay();
     82         if (delay <= 0) {
     83             h.handleMessage(m);
     84         } else {
     85             m.setAsynchronous(true);
     86             h.sendMessageDelayed(m, delay);
     87         }
     88     }
     89 
     90     private long calculateDelay() {
     91         final long sinceFrameStart = System.nanoTime() - mChoreographer.getLastFrameTimeNanos();
     92         return mSurfaceFlingerOffsetMs - sinceFrameStart / 1000000;
     93     }
     94 }
     95