From 503d2bd9a0c64f90fc321f9d65fc65e592f1fa2b Mon Sep 17 00:00:00 2001
From: Robert Carr <racarr@google.com>
Date: Mon, 4 Dec 2017 15:49:47 -0800
Subject: Correct setLayer variants.

Correct a legitimate bug in setLayer where it would fail
to clear a relative layer equal to the new absolute layer. Optimize
all the other variants to not trigger rebuilding of layer stacks in
the case of redundant Z setting.

Test: Existing tests pass.
Change-Id: I6559322017a7b8c5510f8ff265216af3d414696a
---
 services/surfaceflinger/Layer.cpp | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 298f597f34..ff5e6f6e36 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -1109,8 +1109,9 @@ bool Layer::setChildLayer(const sp<Layer>& childLayer, int32_t z) {
     if (childLayer->setLayer(z)) {
         mCurrentChildren.removeAt(idx);
         mCurrentChildren.add(childLayer);
+        return true;
     }
-    return true;
+    return false;
 }
 
 bool Layer::setChildRelativeLayer(const sp<Layer>& childLayer,
@@ -1122,12 +1123,13 @@ bool Layer::setChildRelativeLayer(const sp<Layer>& childLayer,
     if (childLayer->setRelativeLayer(relativeToHandle, relativeZ)) {
         mCurrentChildren.removeAt(idx);
         mCurrentChildren.add(childLayer);
+        return true;
     }
-    return true;
+    return false;
 }
 
 bool Layer::setLayer(int32_t z) {
-    if (mCurrentState.z == z) return false;
+    if (mCurrentState.z == z && !usingRelativeZ(LayerVector::StateSet::Current)) return false;
     mCurrentState.sequence++;
     mCurrentState.z = z;
     mCurrentState.modified = true;
@@ -1158,7 +1160,7 @@ void Layer::addZOrderRelative(const wp<Layer>& relative) {
     setTransactionFlags(eTransactionNeeded);
 }
 
-bool Layer::setRelativeLayer(const sp<IBinder>& relativeToHandle, int32_t z) {
+bool Layer::setRelativeLayer(const sp<IBinder>& relativeToHandle, int32_t relativeZ) {
     sp<Handle> handle = static_cast<Handle*>(relativeToHandle.get());
     if (handle == nullptr) {
         return false;
@@ -1168,9 +1170,14 @@ bool Layer::setRelativeLayer(const sp<IBinder>& relativeToHandle, int32_t z) {
         return false;
     }
 
+    if (mCurrentState.z == relativeZ && usingRelativeZ(LayerVector::StateSet::Current) &&
+            mCurrentState.zOrderRelativeOf == relative) {
+        return false;
+    }
+
     mCurrentState.sequence++;
     mCurrentState.modified = true;
-    mCurrentState.z = z;
+    mCurrentState.z = relativeZ;
 
     auto oldZOrderRelativeOf = mCurrentState.zOrderRelativeOf.promote();
     if (oldZOrderRelativeOf != nullptr) {
-- 
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