From 0b19a7370a1121219cef2d34b69676e1dee4c547 Mon Sep 17 00:00:00 2001
From: John Reck <jreck@google.com>
Date: Thu, 7 Mar 2019 17:18:25 -0800
Subject: [PATCH] Re-enable empty damage drop optimization

Fixes: 113796161
Test: device seemed to behave correctly?
Change-Id: Id43e1eaad29d07c06c1003c0653e5d1ee7084cfe
---
 libs/hwui/renderthread/CanvasContext.cpp | 23 ++++++++++++++++++-----
 libs/hwui/renderthread/CanvasContext.h   |  1 +
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/libs/hwui/renderthread/CanvasContext.cpp b/libs/hwui/renderthread/CanvasContext.cpp
index 8e57a3a119e3b..091775dbe7908 100644
--- a/libs/hwui/renderthread/CanvasContext.cpp
+++ b/libs/hwui/renderthread/CanvasContext.cpp
@@ -401,11 +401,11 @@ void CanvasContext::draw() {
     SkRect dirty;
     mDamageAccumulator.finish(&dirty);
 
-    // TODO: Re-enable after figuring out cause of b/22592975
-    //    if (dirty.isEmpty() && Properties::skipEmptyFrames) {
-    //        mCurrentFrameInfo->addFlag(FrameInfoFlags::SkippedFrame);
-    //        return;
-    //    }
+    if (dirty.isEmpty() && Properties::skipEmptyFrames
+            && !surfaceRequiresRedraw()) {
+        mCurrentFrameInfo->addFlag(FrameInfoFlags::SkippedFrame);
+        return;
+    }
 
     mCurrentFrameInfo->markIssueDrawCommandsStart();
 
@@ -638,6 +638,19 @@ int64_t CanvasContext::getFrameNumber() {
     return mFrameNumber;
 }
 
+bool CanvasContext::surfaceRequiresRedraw() {
+    if (!mNativeSurface) return false;
+    if (mHaveNewSurface) return true;
+
+    int width = -1;
+    int height = -1;
+    ReliableSurface* surface = mNativeSurface.get();
+    surface->query(NATIVE_WINDOW_WIDTH, &width);
+    surface->query(NATIVE_WINDOW_HEIGHT, &height);
+
+    return width == mLastFrameWidth && height == mLastFrameHeight;
+}
+
 SkRect CanvasContext::computeDirtyRect(const Frame& frame, SkRect* dirty) {
     if (frame.width() != mLastFrameWidth || frame.height() != mLastFrameHeight) {
         // can't rely on prior content of window if viewport size changes
diff --git a/libs/hwui/renderthread/CanvasContext.h b/libs/hwui/renderthread/CanvasContext.h
index db97763acd8bc..4da0eac85bb0d 100644
--- a/libs/hwui/renderthread/CanvasContext.h
+++ b/libs/hwui/renderthread/CanvasContext.h
@@ -217,6 +217,7 @@ private:
     void freePrefetchedLayers();
 
     bool isSwapChainStuffed();
+    bool surfaceRequiresRedraw();
 
     SkRect computeDirtyRect(const Frame& frame, SkRect* dirty);