From 501ff9acfe9dd656c1fb6d82ec0533c3244fd88b Mon Sep 17 00:00:00 2001
From: John Reck <jreck@google.com>
Date: Fri, 17 Jun 2016 12:57:12 -0700
Subject: [PATCH] Avoid re-calculating vsync mid-frame

Fixes: 29072773

By using computeFrameTime AnimationContext would
potentially end up modifying the latest vsync if
a very-slow frame was received from the UI thread.

This could potentially desync animations that were
RT & UI thread 'synchronized', but more significantly
it would confuse the swap chain which tries to only
draw one frame per vsync causing unneccessary frame
drops.

Change-Id: Ibd2ec3157ce32fee1eec8d56837c45a35e622895
---
 libs/hwui/AnimationContext.cpp      | 2 +-
 libs/hwui/renderthread/TimeLord.cpp | 4 ----
 libs/hwui/renderthread/TimeLord.h   | 1 -
 3 files changed, 1 insertion(+), 6 deletions(-)

diff --git a/libs/hwui/AnimationContext.cpp b/libs/hwui/AnimationContext.cpp
index 097be08faaad4..5759ccd85464f 100644
--- a/libs/hwui/AnimationContext.cpp
+++ b/libs/hwui/AnimationContext.cpp
@@ -63,7 +63,7 @@ void AnimationContext::startFrame(TreeInfo::TraversalMode mode) {
         mCurrentFrameAnimations.mNextHandle = head;
         head->mPreviousHandle = &mCurrentFrameAnimations;
     }
-    mFrameTimeMs = mClock.computeFrameTimeMs();
+    mFrameTimeMs = ns2ms(mClock.latestVsync());
 }
 
 void AnimationContext::runRemainingAnimations(TreeInfo& info) {
diff --git a/libs/hwui/renderthread/TimeLord.cpp b/libs/hwui/renderthread/TimeLord.cpp
index f846d6a44473b..6c2575f699bb9 100644
--- a/libs/hwui/renderthread/TimeLord.cpp
+++ b/libs/hwui/renderthread/TimeLord.cpp
@@ -43,10 +43,6 @@ nsecs_t TimeLord::computeFrameTimeNanos() {
     return mFrameTimeNanos;
 }
 
-nsecs_t TimeLord::computeFrameTimeMs() {
-    return nanoseconds_to_milliseconds(computeFrameTimeNanos());
-}
-
 } /* namespace renderthread */
 } /* namespace uirenderer */
 } /* namespace android */
diff --git a/libs/hwui/renderthread/TimeLord.h b/libs/hwui/renderthread/TimeLord.h
index 5464399234fb3..68a0f7f971b96 100644
--- a/libs/hwui/renderthread/TimeLord.h
+++ b/libs/hwui/renderthread/TimeLord.h
@@ -34,7 +34,6 @@ public:
     // returns true if the vsync is newer, false if it was rejected for staleness
     bool vsyncReceived(nsecs_t vsync);
     nsecs_t latestVsync() { return mFrameTimeNanos; }
-    nsecs_t computeFrameTimeMs();
     nsecs_t computeFrameTimeNanos();
 
 private: