commit 05289c2b78d21308a95ea6ef8f1d8f24359147cd
author Pablo Ceballos <pceballos@google.com> Thu Apr 14 15:49:55 2016 -0700
committer Pablo Ceballos <pceballos@google.com> Thu Apr 14 16:01:23 2016 -0700
tree 4f17199a81080babed45f380464b21e205fb0c57
parent 9ffa1a4da16edc23067070f5605917ddd57739e8

SF: Don't pop pending state into mCurrentState

Let mCurrentState always represent the most up to date state, even if
there are transactions we don't want to commit yet. Past snapshots of
the state are kept in mPendingState. In doTransaction(), grab the
correct pending state from mPendingState, but save it to a local copy
that gets committed rather than overriding mCurrentState.

Bug 27205755

Change-Id: Ib0ea809da1954409787c52b8f41d7963a57a6a4c

services/surfaceflinger/Layer.cpp

diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index a2c0462..90ab70d 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -1309,16 +1309,16 @@
     mPendingStates.push_back(mCurrentState);
 }
 
-void Layer::popPendingState() {
-    auto oldFlags = mCurrentState.flags;
-    mCurrentState = mPendingStates[0];
-    mCurrentState.flags = (oldFlags & ~mCurrentState.mask) |
-            (mCurrentState.flags & mCurrentState.mask);
+void Layer::popPendingState(State* stateToCommit) {
+    auto oldFlags = stateToCommit->flags;
+    *stateToCommit = mPendingStates[0];
+    stateToCommit->flags = (oldFlags & ~stateToCommit->mask) |
+            (stateToCommit->flags & stateToCommit->mask);
 
     mPendingStates.removeAt(0);
 }
 
-bool Layer::applyPendingStates() {
+bool Layer::applyPendingStates(State* stateToCommit) {
     bool stateUpdateAvailable = false;
     while (!mPendingStates.empty()) {
         if (mPendingStates[0].handle != nullptr) {
@@ -1327,7 +1327,7 @@
                 // will be visually wrong, but it should keep us from getting
                 // into too much trouble.
                 ALOGE("[%s] No local sync point found", mName.string());
-                popPendingState();
+                popPendingState(stateToCommit);
                 stateUpdateAvailable = true;
                 continue;
             }
@@ -1345,7 +1345,7 @@
 
             if (mRemoteSyncPoints.front()->frameIsAvailable()) {
                 // Apply the state update
-                popPendingState();
+                popPendingState(stateToCommit);
                 stateUpdateAvailable = true;
 
                 // Signal our end of the sync point and then dispose of it
@@ -1355,7 +1355,7 @@
                 break;
             }
         } else {
-            popPendingState();
+            popPendingState(stateToCommit);
             stateUpdateAvailable = true;
         }
     }
@@ -1385,12 +1385,12 @@
     ATRACE_CALL();
 
     pushPendingState();
-    if (!applyPendingStates()) {
+    Layer::State c = getCurrentState();
+    if (!applyPendingStates(&c)) {
         return 0;
     }
 
     const Layer::State& s(getDrawingState());
-    const Layer::State& c(getCurrentState());
 
     const bool sizeChanged = (c.requested.w != s.requested.w) ||
                              (c.requested.h != s.requested.h);
@@ -1454,8 +1454,7 @@
     // this is used by Layer, which special cases resizes.
     if (flags & eDontUpdateGeometryState)  {
     } else {
-        Layer::State& editCurrentState(getCurrentState());
-        editCurrentState.active = c.requested;
+        c.active = c.requested;
     }
 
     if (s.active != c.active) {
@@ -1475,12 +1474,12 @@
     }
 
     // Commit the transaction
-    commitTransaction();
+    commitTransaction(c);
     return flags;
 }
 
-void Layer::commitTransaction() {
-    mDrawingState = mCurrentState;
+void Layer::commitTransaction(const State& stateToCommit) {
+    mDrawingState = stateToCommit;
 }
 
 uint32_t Layer::getTransactionFlags(uint32_t flags) {