From f3f7db6346323ca3ec4ec449a2622adddc6306b4 Mon Sep 17 00:00:00 2001
From: Jeff Brown <jeffbrown@google.com>
Date: Fri, 31 Aug 2012 02:18:38 -0700
Subject: Allow global transactions to nest.

This change fixes a number of small glitches that can occur when
multiple components in the same process are updating surfaces.
One would expect that updates to disjoint sets of surfaces would
not collide but this is not the case.  The first component to
close the global transaction causes all pending updates to
be applied, including those that another component might not
have finished setting up if it also had an open transaction
at the same time.

Change-Id: I99345958581abbe0e1e325a5bcba37e8941a313a
---
 libs/gui/SurfaceComposerClient.cpp | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

(limited to 'libs/gui/SurfaceComposerClient.cpp')

diff --git a/libs/gui/SurfaceComposerClient.cpp b/libs/gui/SurfaceComposerClient.cpp
index 80dd6ee96a..746057b429 100644
--- a/libs/gui/SurfaceComposerClient.cpp
+++ b/libs/gui/SurfaceComposerClient.cpp
@@ -115,13 +115,15 @@ class Composer : public Singleton<Composer>
     SortedVector<ComposerState> mComposerStates;
     SortedVector<DisplayState > mDisplayStates;
     uint32_t                    mForceSynchronous;
+    uint32_t                    mTransactionNestCount;
     bool                        mAnimation;
 
     Composer() : Singleton<Composer>(),
-        mForceSynchronous(0),
+        mForceSynchronous(0), mTransactionNestCount(0),
         mAnimation(false)
     { }
 
+    void openGlobalTransactionImpl();
     void closeGlobalTransactionImpl(bool synchronous);
     void setAnimationTransactionImpl();
 
@@ -166,6 +168,10 @@ public:
         Composer::getInstance().setAnimationTransactionImpl();
     }
 
+    static void openGlobalTransaction() {
+        Composer::getInstance().openGlobalTransactionImpl();
+    }
+
     static void closeGlobalTransaction(bool synchronous) {
         Composer::getInstance().closeGlobalTransactionImpl(synchronous);
     }
@@ -184,6 +190,13 @@ sp<IBinder> Composer::getBuiltInDisplay(int32_t id) {
     return ComposerService::getComposerService()->getBuiltInDisplay(id);
 }
 
+void Composer::openGlobalTransactionImpl() {
+    { // scope for the lock
+        Mutex::Autolock _l(mLock);
+        mTransactionNestCount += 1;
+    }
+}
+
 void Composer::closeGlobalTransactionImpl(bool synchronous) {
     sp<ISurfaceComposer> sm(ComposerService::getComposerService());
 
@@ -193,13 +206,21 @@ void Composer::closeGlobalTransactionImpl(bool synchronous) {
 
     { // scope for the lock
         Mutex::Autolock _l(mLock);
+        mForceSynchronous |= synchronous;
+        if (!mTransactionNestCount) {
+            ALOGW("At least one call to closeGlobalTransaction() was not matched by a prior "
+                    "call to openGlobalTransaction().");
+        } else if (--mTransactionNestCount) {
+            return;
+        }
+
         transaction = mComposerStates;
         mComposerStates.clear();
 
         displayTransaction = mDisplayStates;
         mDisplayStates.clear();
 
-        if (synchronous || mForceSynchronous) {
+        if (mForceSynchronous) {
             flags |= ISurfaceComposer::eSynchronous;
         }
         if (mAnimation) {
@@ -483,7 +504,7 @@ inline Composer& SurfaceComposerClient::getComposer() {
 // ----------------------------------------------------------------------------
 
 void SurfaceComposerClient::openGlobalTransaction() {
-    // Currently a no-op
+    Composer::openGlobalTransaction();
 }
 
 void SurfaceComposerClient::closeGlobalTransaction(bool synchronous) {
-- 
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