Merge "separate transactions from updates"

11 files changed, 257 insertions, 172 deletions

diff --git a/include/gui/DisplayEventReceiver.h b/include/gui/DisplayEventReceiver.h
index a281377..7bca8d6 100644
--- a/include/gui/DisplayEventReceiver.h
+++ b/include/gui/DisplayEventReceiver.h
@@ -95,6 +95,8 @@ public:
      * should be destroyed and getEvents() shouldn't be called again.
      */
     ssize_t getEvents(Event* events, size_t count);
+    static ssize_t getEvents(const sp<BitTube>& dataChannel,
+            Event* events, size_t count);
 
     /*
      * setVsyncRate() sets the Event::VSync delivery rate. A value of
diff --git a/libs/gui/DisplayEventReceiver.cpp b/libs/gui/DisplayEventReceiver.cpp
index 3b3ccaa..6a4763d 100644
--- a/libs/gui/DisplayEventReceiver.cpp
+++ b/libs/gui/DisplayEventReceiver.cpp
@@ -80,7 +80,13 @@ status_t DisplayEventReceiver::requestNextVsync() {
 
 ssize_t DisplayEventReceiver::getEvents(DisplayEventReceiver::Event* events,
         size_t count) {
-    ssize_t size = mDataChannel->read(events, sizeof(events[0])*count);
+    return DisplayEventReceiver::getEvents(mDataChannel, events, count);
+}
+
+ssize_t DisplayEventReceiver::getEvents(const sp<BitTube>& dataChannel,
+        Event* events, size_t count)
+{
+    ssize_t size = dataChannel->read(events, sizeof(events[0])*count);
     ALOGE_IF(size<0,
             "DisplayEventReceiver::getEvents error (%s)",
             strerror(-size));
diff --git a/services/surfaceflinger/Android.mk b/services/surfaceflinger/Android.mk
index fc211e5..8b4c074 100644
--- a/services/surfaceflinger/Android.mk
+++ b/services/surfaceflinger/Android.mk
@@ -32,7 +32,6 @@ ifeq ($(TARGET_BOARD_PLATFORM), omap3)
 endif
 ifeq ($(TARGET_BOARD_PLATFORM), omap4)
 	LOCAL_CFLAGS += -DHAS_CONTEXT_PRIORITY
-	LOCAL_CFLAGS += -DUSE_TRIPLE_BUFFERING=1
 endif
 ifeq ($(TARGET_BOARD_PLATFORM), s5pc110)
 	LOCAL_CFLAGS += -DHAS_CONTEXT_PRIORITY -DNEVER_DEFAULT_TO_ASYNC_MODE
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 9c04d59..64f72d5 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -55,6 +55,7 @@ Layer::Layer(SurfaceFlinger* flinger,
         mCurrentTransform(0),
         mCurrentScalingMode(NATIVE_WINDOW_SCALING_MODE_FREEZE),
         mCurrentOpacity(true),
+        mRefreshPending(0),
         mFrameLatencyNeeded(false),
         mFrameLatencyOffset(0),
         mFormat(PIXEL_FORMAT_NONE),
@@ -97,12 +98,7 @@ void Layer::onFirstRef()
     mSurfaceTexture = new SurfaceTextureLayer(mTextureName, this);
     mSurfaceTexture->setFrameAvailableListener(new FrameQueuedListener(this));
     mSurfaceTexture->setSynchronousMode(true);
-#ifdef USE_TRIPLE_BUFFERING
-#warning "using triple buffering"
-    mSurfaceTexture->setBufferCountServer(3);
-#else
     mSurfaceTexture->setBufferCountServer(2);
-#endif
 }
 
 Layer::~Layer()
@@ -113,7 +109,7 @@ Layer::~Layer()
 
 void Layer::onFrameQueued() {
     android_atomic_inc(&mQueuedFrames);
-    mFlinger->signalEvent();
+    mFlinger->signalLayerUpdate();
 }
 
 // called with SurfaceFlinger::mStateLock as soon as the layer is entered
@@ -407,16 +403,37 @@ bool Layer::isCropped() const {
 // pageflip handling...
 // ----------------------------------------------------------------------------
 
+bool Layer::onPreComposition()
+{
+    // if there was more than one pending update, request a refresh
+    if (mRefreshPending >= 2) {
+        mRefreshPending = 0;
+        return true;
+    }
+    mRefreshPending = 0;
+    return false;
+}
+
 void Layer::lockPageFlip(bool& recomputeVisibleRegions)
 {
     if (mQueuedFrames > 0) {
+
+        // if we've already called updateTexImage() without going through
+        // a composition step, we have to skip this layer at this point
+        // because we cannot call updateTeximage() without a corresponding
+        // compositionComplete() call.
+        // we'll trigger an update in onPreComposition().
+        if (mRefreshPending++) {
+            return;
+        }
+
         // Capture the old state of the layer for comparisons later
         const bool oldOpacity = isOpaque();
         sp<GraphicBuffer> oldActiveBuffer = mActiveBuffer;
 
         // signal another event if we have more frames pending
         if (android_atomic_dec(&mQueuedFrames) > 1) {
-            mFlinger->signalEvent();
+            mFlinger->signalLayerUpdate();
         }
 
         if (mSurfaceTexture->updateTexImage() < NO_ERROR) {
@@ -519,6 +536,10 @@ void Layer::lockPageFlip(bool& recomputeVisibleRegions)
 void Layer::unlockPageFlip(
         const Transform& planeTransform, Region& outDirtyRegion)
 {
+    if (mRefreshPending >= 2) {
+        return;
+    }
+
     Region dirtyRegion(mPostedDirtyRegion);
     if (!dirtyRegion.isEmpty()) {
         mPostedDirtyRegion.clear();
@@ -552,9 +573,9 @@ void Layer::dump(String8& result, char* buffer, size_t SIZE) const
     snprintf(buffer, SIZE,
             "      "
             "format=%2d, activeBuffer=[%4ux%4u:%4u,%3X],"
-            " transform-hint=0x%02x, queued-frames=%d\n",
+            " transform-hint=0x%02x, queued-frames=%d, mRefreshPending=%d\n",
             mFormat, w0, h0, s0,f0,
-            getTransformHint(), mQueuedFrames);
+            getTransformHint(), mQueuedFrames, mRefreshPending);
 
     result.append(buffer);
 
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 2dd4da1..bf30608 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -80,6 +80,7 @@ public:
     virtual wp<IBinder> getSurfaceTextureBinder() const;
 
     virtual void onLayerDisplayed();
+    virtual bool onPreComposition();
 
     // only for debugging
     inline const sp<GraphicBuffer>& getActiveBuffer() const { return mActiveBuffer; }
@@ -115,14 +116,17 @@ private:
     uint32_t mCurrentTransform;
     uint32_t mCurrentScalingMode;
     bool mCurrentOpacity;
+    size_t mRefreshPending;
     bool mFrameLatencyNeeded;
     int mFrameLatencyOffset;
+
     struct Statistics {
         Statistics() : timestamp(0), set(0), vsync(0) { }
         nsecs_t timestamp;  // buffer timestamp
         nsecs_t set;        // buffer displayed timestamp
         nsecs_t vsync;      // vsync immediately before set
     };
+
     // protected by mLock
     Statistics mFrameStats[128];
 
diff --git a/services/surfaceflinger/LayerBase.cpp b/services/surfaceflinger/LayerBase.cpp
index d32fcdd..44aafdf 100644
--- a/services/surfaceflinger/LayerBase.cpp
+++ b/services/surfaceflinger/LayerBase.cpp
@@ -47,8 +47,7 @@ LayerBase::LayerBase(SurfaceFlinger* flinger, DisplayID display)
       mOrientation(0),
       mPlaneOrientation(0),
       mTransactionFlags(0),
-      mPremultipliedAlpha(true), mName("unnamed"), mDebug(false),
-      mInvalidate(0)
+      mPremultipliedAlpha(true), mName("unnamed"), mDebug(false)
 {
     const DisplayHardware& hw(flinger->graphicPlane(0).displayHardware());
     mFlags = hw.getFlags();
@@ -262,23 +261,11 @@ void LayerBase::validateVisibility(const Transform& planeTransform)
     mTransformedBounds = tr.makeBounds(w, h);
 }
 
-void LayerBase::lockPageFlip(bool& recomputeVisibleRegions)
-{
+void LayerBase::lockPageFlip(bool& recomputeVisibleRegions) {
 }
 
 void LayerBase::unlockPageFlip(
-        const Transform& planeTransform, Region& outDirtyRegion)
-{
-    if ((android_atomic_and(~1, &mInvalidate)&1) == 1) {
-        outDirtyRegion.orSelf(visibleRegionScreen);
-    }
-}
-
-void LayerBase::invalidate()
-{
-    if ((android_atomic_or(1, &mInvalidate)&1) == 0) {
-        mFlinger->signalEvent();
-    }
+        const Transform& planeTransform, Region& outDirtyRegion) {
 }
 
 void LayerBase::drawRegion(const Region& reg) const
diff --git a/services/surfaceflinger/LayerBase.h b/services/surfaceflinger/LayerBase.h
index 6b62c9d..b8f7680 100644
--- a/services/surfaceflinger/LayerBase.h
+++ b/services/surfaceflinger/LayerBase.h
@@ -103,8 +103,6 @@ public:
             Rect visibleBounds() const;
             void drawRegion(const Region& reg) const;
 
-            void invalidate();
-
     virtual sp<LayerBaseClient> getLayerBaseClient() const { return 0; }
     virtual sp<Layer> getLayer() const { return 0; }
 
@@ -204,9 +202,16 @@ public:
 
     /** called with the state lock when the surface is removed from the
      *  current list */
-    virtual void onRemoved() { };
+    virtual void onRemoved() { }
 
-    virtual void onLayerDisplayed() { };
+    /** called after page-flip
+     */
+    virtual void onLayerDisplayed() { }
+
+    /** called before composition.
+     * returns true if the layer has pending updates.
+     */
+    virtual bool onPreComposition() { return false; }
 
     /** always call base class first */
     virtual void dump(String8& result, char* scratch, size_t size) const;
@@ -275,10 +280,6 @@ protected:
     mutable     bool            mDebug;
 
 
-                // atomic
-    volatile    int32_t         mInvalidate;
-                
-
 public:
     // called from class SurfaceFlinger
     virtual ~LayerBase();
diff --git a/services/surfaceflinger/MessageQueue.cpp b/services/surfaceflinger/MessageQueue.cpp
index 70711e7..1ff3567 100644
--- a/services/surfaceflinger/MessageQueue.cpp
+++ b/services/surfaceflinger/MessageQueue.cpp
@@ -29,6 +29,7 @@
 
 #include "MessageQueue.h"
 #include "EventThread.h"
+#include "SurfaceFlinger.h"
 
 namespace android {
 
@@ -48,14 +49,47 @@ void MessageBase::handleMessage(const Message&) {
 
 // ---------------------------------------------------------------------------
 
+void MessageQueue::Handler::signalRefresh() {
+    if ((android_atomic_or(eventMaskRefresh, &mEventMask) & eventMaskRefresh) == 0) {
+        mQueue.mLooper->sendMessage(this, Message(MessageQueue::REFRESH));
+    }
+}
+
+void MessageQueue::Handler::signalInvalidate() {
+    if ((android_atomic_or(eventMaskInvalidate, &mEventMask) & eventMaskInvalidate) == 0) {
+        mQueue.mLooper->sendMessage(this, Message(MessageQueue::INVALIDATE));
+    }
+}
+
+void MessageQueue::Handler::handleMessage(const Message& message) {
+    switch (message.what) {
+        case INVALIDATE:
+            android_atomic_and(~eventMaskInvalidate, &mEventMask);
+            mQueue.mFlinger->onMessageReceived(message.what);
+            break;
+        case REFRESH:
+            android_atomic_and(~eventMaskRefresh, &mEventMask);
+            mQueue.mFlinger->onMessageReceived(message.what);
+            break;
+    }
+}
+
+// ---------------------------------------------------------------------------
+
 MessageQueue::MessageQueue()
-    : mLooper(new Looper(true)), mWorkPending(0)
 {
 }
 
 MessageQueue::~MessageQueue() {
 }
 
+void MessageQueue::init(const sp<SurfaceFlinger>& flinger)
+{
+    mFlinger = flinger;
+    mLooper = new Looper(true);
+    mHandler = new Handler(*this);
+}
+
 void MessageQueue::setEventThread(const sp<EventThread>& eventThread)
 {
     mEventThread = eventThread;
@@ -68,25 +102,16 @@ void MessageQueue::setEventThread(const sp<EventThread>& eventThread)
 void MessageQueue::waitMessage() {
     do {
         IPCThreadState::self()->flushCommands();
-
         int32_t ret = mLooper->pollOnce(-1);
         switch (ret) {
             case ALOOPER_POLL_WAKE:
             case ALOOPER_POLL_CALLBACK:
-                // callback and/or wake
-                if (android_atomic_and(0, &mWorkPending)) {
-                    return;
-                }
                 continue;
-
-            case ALOOPER_POLL_TIMEOUT:
-                // timeout (should not happen)
-                continue;
-
             case ALOOPER_POLL_ERROR:
                 ALOGE("ALOOPER_POLL_ERROR");
+            case ALOOPER_POLL_TIMEOUT:
+                // timeout (should not happen)
                 continue;
-
             default:
                 // should not happen
                 ALOGE("Looper::pollOnce() returned unknown status %d", ret);
@@ -107,15 +132,12 @@ status_t MessageQueue::postMessage(
     return NO_ERROR;
 }
 
-void MessageQueue::scheduleWorkASAP() {
-    if (android_atomic_or(1, &mWorkPending) == 0) {
-        mLooper->wake();
-   }
+void MessageQueue::invalidate() {
+    mHandler->signalInvalidate();
 }
 
-status_t MessageQueue::invalidate() {
+void MessageQueue::refresh() {
     mEvents->requestNextVsync();
-    return NO_ERROR;
 }
 
 int MessageQueue::cb_eventReceiver(int fd, int events, void* data) {
@@ -126,10 +148,10 @@ int MessageQueue::cb_eventReceiver(int fd, int events, void* data) {
 int MessageQueue::eventReceiver(int fd, int events) {
     ssize_t n;
     DisplayEventReceiver::Event buffer[8];
-    while ((n = getEvents(buffer, 8)) > 0) {
+    while ((n = DisplayEventReceiver::getEvents(mEventTube, buffer, 8)) > 0) {
         for (int i=0 ; i<n ; i++) {
             if (buffer[i].header.type == DisplayEventReceiver::DISPLAY_EVENT_VSYNC) {
-                scheduleWorkASAP();
+                mHandler->signalRefresh();
                 break;
             }
         }
@@ -137,24 +159,6 @@ int MessageQueue::eventReceiver(int fd, int events) {
     return 1;
 }
 
-ssize_t MessageQueue::getEvents(
-        DisplayEventReceiver::Event* events, size_t count)
-{
-    ssize_t size = mEventTube->read(events, sizeof(events[0])*count);
-    ALOGE_IF(size<0, "MessageQueue::getEvents error (%s)", strerror(-size));
-    if (size >= 0) {
-        // Note: if (size % sizeof(events[0])) != 0, we've got a
-        // partial read. This can happen if the queue filed up (ie: if we
-        // didn't pull from it fast enough).
-        // We discard the partial event and rely on the sender to
-        // re-send the event if appropriate (some events, like VSYNC
-        // can be lost forever).
-        // returns number of events read
-        size /= sizeof(events[0]);
-    }
-    return size;
-}
-
 // ---------------------------------------------------------------------------
 
 }; // namespace android
diff --git a/services/surfaceflinger/MessageQueue.h b/services/surfaceflinger/MessageQueue.h
index 5ea197d..ea29e7e 100644
--- a/services/surfaceflinger/MessageQueue.h
+++ b/services/surfaceflinger/MessageQueue.h
@@ -33,6 +33,7 @@ namespace android {
 
 class IDisplayEventConnection;
 class EventThread;
+class SurfaceFlinger;
 
 // ---------------------------------------------------------------------------
 
@@ -59,25 +60,48 @@ private:
 // ---------------------------------------------------------------------------
 
 class MessageQueue {
+    class Handler : public MessageHandler {
+        enum {
+            eventMaskInvalidate = 0x1,
+            eventMaskRefresh    = 0x2
+        };
+        MessageQueue& mQueue;
+        int32_t mEventMask;
+    public:
+        Handler(MessageQueue& queue) : mQueue(queue), mEventMask(0) { }
+        virtual void handleMessage(const Message& message);
+        void signalRefresh();
+        void signalInvalidate();
+    };
+
+    friend class Handler;
+
+    sp<SurfaceFlinger> mFlinger;
     sp<Looper> mLooper;
     sp<EventThread> mEventThread;
     sp<IDisplayEventConnection> mEvents;
     sp<BitTube> mEventTube;
-    int32_t mWorkPending;
+    sp<Handler> mHandler;
+
 
     static int cb_eventReceiver(int fd, int events, void* data);
     int eventReceiver(int fd, int events);
-    ssize_t getEvents(DisplayEventReceiver::Event* events, size_t count);
-    void scheduleWorkASAP();
 
 public:
+    enum {
+        INVALIDATE = 0,
+        REFRESH    = 1,
+    };
+
     MessageQueue();
     ~MessageQueue();
+    void init(const sp<SurfaceFlinger>& flinger);
     void setEventThread(const sp<EventThread>& events);
 
     void waitMessage();
     status_t postMessage(const sp<MessageBase>& message, nsecs_t reltime=0);
-    status_t invalidate();
+    void invalidate();
+    void refresh();
 };
 
 // ---------------------------------------------------------------------------
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index ff70ec3..870235b 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -125,11 +125,34 @@ void SurfaceFlinger::init()
     ALOGI_IF(mDebugDDMS,         "DDMS debugging enabled");
 }
 
+void SurfaceFlinger::onFirstRef()
+{
+    mEventQueue.init(this);
+
+    run("SurfaceFlinger", PRIORITY_URGENT_DISPLAY);
+
+    // Wait for the main thread to be done with its initialization
+    mReadyToRunBarrier.wait();
+}
+
+
 SurfaceFlinger::~SurfaceFlinger()
 {
     glDeleteTextures(1, &mWormholeTexName);
 }
 
+void SurfaceFlinger::binderDied(const wp<IBinder>& who)
+{
+    // the window manager died on us. prepare its eulogy.
+
+    // reset screen orientation
+    Vector<ComposerState> state;
+    setTransactionState(state, eOrientationDefault, 0);
+
+    // restart the boot-animation
+    property_set("ctl.start", "bootanim");
+}
+
 sp<IMemoryHeap> SurfaceFlinger::getCblk() const
 {
     return mServerHeap;
@@ -183,26 +206,6 @@ void SurfaceFlinger::bootFinished()
     property_set("ctl.stop", "bootanim");
 }
 
-void SurfaceFlinger::binderDied(const wp<IBinder>& who)
-{
-    // the window manager died on us. prepare its eulogy.
-
-    // reset screen orientation
-    Vector<ComposerState> state;
-    setTransactionState(state, eOrientationDefault, 0);
-
-    // restart the boot-animation
-    property_set("ctl.start", "bootanim");
-}
-
-void SurfaceFlinger::onFirstRef()
-{
-    run("SurfaceFlinger", PRIORITY_URGENT_DISPLAY);
-
-    // Wait for the main thread to be done with its initialization
-    mReadyToRunBarrier.wait();
-}
-
 static inline uint16_t pack565(int r, int g, int b) {
     return (r<<11)|(g<<5)|b;
 }
@@ -311,34 +314,6 @@ status_t SurfaceFlinger::readyToRun()
 }
 
 // ----------------------------------------------------------------------------
-#if 0
-#pragma mark -
-#pragma mark Events Handler
-#endif
-
-void SurfaceFlinger::waitForEvent() {
-    mEventQueue.waitMessage();
-}
-
-void SurfaceFlinger::signalEvent() {
-    mEventQueue.invalidate();
-}
-
-status_t SurfaceFlinger::postMessageAsync(const sp<MessageBase>& msg,
-        nsecs_t reltime, uint32_t flags) {
-    return mEventQueue.postMessage(msg, reltime);
-}
-
-status_t SurfaceFlinger::postMessageSync(const sp<MessageBase>& msg,
-        nsecs_t reltime, uint32_t flags) {
-    status_t res = mEventQueue.postMessage(msg, reltime);
-    if (res == NO_ERROR) {
-        msg->wait();
-    }
-    return res;
-}
-
-// ----------------------------------------------------------------------------
 
 bool SurfaceFlinger::authenticateSurfaceTexture(
         const sp<ISurfaceTexture>& surfaceTexture) const {
@@ -388,52 +363,91 @@ sp<IDisplayEventConnection> SurfaceFlinger::createDisplayEventConnection() {
 }
 
 // ----------------------------------------------------------------------------
-#if 0
-#pragma mark -
-#pragma mark Main loop
-#endif
+
+void SurfaceFlinger::waitForEvent() {
+    mEventQueue.waitMessage();
+}
+
+void SurfaceFlinger::signalTransaction() {
+    mEventQueue.invalidate();
+}
+
+void SurfaceFlinger::signalLayerUpdate() {
+    mEventQueue.invalidate();
+}
+
+void SurfaceFlinger::signalRefresh() {
+    mEventQueue.refresh();
+}
+
+status_t SurfaceFlinger::postMessageAsync(const sp<MessageBase>& msg,
+        nsecs_t reltime, uint32_t flags) {
+    return mEventQueue.postMessage(msg, reltime);
+}
+
+status_t SurfaceFlinger::postMessageSync(const sp<MessageBase>& msg,
+        nsecs_t reltime, uint32_t flags) {
+    status_t res = mEventQueue.postMessage(msg, reltime);
+    if (res == NO_ERROR) {
+        msg->wait();
+    }
+    return res;
+}
 
 bool SurfaceFlinger::threadLoop()
 {
     waitForEvent();
+    return true;
+}
 
-    // check for transactions
-    if (CC_UNLIKELY(mConsoleSignals)) {
-        handleConsoleEvents();
-    }
+void SurfaceFlinger::onMessageReceived(int32_t what)
+{
+    switch (what) {
+        case MessageQueue::INVALIDATE: {
+            // check for transactions
+            if (CC_UNLIKELY(mConsoleSignals)) {
+                handleConsoleEvents();
+            }
 
-    // if we're in a global transaction, don't do anything.
-    const uint32_t mask = eTransactionNeeded | eTraversalNeeded;
-    uint32_t transactionFlags = peekTransactionFlags(mask);
-    if (CC_UNLIKELY(transactionFlags)) {
-        handleTransaction(transactionFlags);
-    }
+            // if we're in a global transaction, don't do anything.
+            const uint32_t mask = eTransactionNeeded | eTraversalNeeded;
+            uint32_t transactionFlags = peekTransactionFlags(mask);
+            if (CC_UNLIKELY(transactionFlags)) {
+                handleTransaction(transactionFlags);
+            }
 
-    // post surfaces (if needed)
-    handlePageFlip();
+            // post surfaces (if needed)
+            handlePageFlip();
 
-    if (mDirtyRegion.isEmpty()) {
-        // nothing new to do.
-        return true;
-    }
+            if (!mDirtyRegion.isEmpty()) {
+                signalRefresh();
+            }
+        } break;
 
-    if (CC_UNLIKELY(mHwWorkListDirty)) {
-        // build the h/w work list
-        handleWorkList();
-    }
+        case MessageQueue::REFRESH: {
+            if (!mDirtyRegion.isEmpty()) {
+                // NOTE: it is mandatory to call hw.compositionComplete()
+                // after handleRefresh()
+                handleRefresh();
 
-    const DisplayHardware& hw(graphicPlane(0).displayHardware());
-    if (CC_LIKELY(hw.canDraw())) {
-        // repaint the framebuffer (if needed)
-        handleRepaint();
-        // inform the h/w that we're done compositing
-        hw.compositionComplete();
-        postFramebuffer();
-    } else {
-        // pretend we did the post
-        hw.compositionComplete();
+                const DisplayHardware& hw(graphicPlane(0).displayHardware());
+                if (CC_UNLIKELY(mHwWorkListDirty)) {
+                    // build the h/w work list
+                    handleWorkList();
+                }
+                if (CC_LIKELY(hw.canDraw())) {
+                    // repaint the framebuffer (if needed)
+                    handleRepaint();
+                    // inform the h/w that we're done compositing
+                    hw.compositionComplete();
+                    postFramebuffer();
+                } else {
+                    // pretend we did the post
+                    hw.compositionComplete();
+                }
+            }
+        } break;
     }
-    return true;
 }
 
 void SurfaceFlinger::postFramebuffer()
@@ -717,13 +731,13 @@ void SurfaceFlinger::commitTransaction()
 
 void SurfaceFlinger::handlePageFlip()
 {
-    bool visibleRegions = mVisibleRegionsDirty;
+    const DisplayHardware& hw = graphicPlane(0).displayHardware();
+    const Region screenRegion(hw.bounds());
+
     const LayerVector& currentLayers(mDrawingState.layersSortedByZ);
-    visibleRegions |= lockPageFlip(currentLayers);
+    const bool visibleRegions = lockPageFlip(currentLayers);
 
-        const DisplayHardware& hw = graphicPlane(0).displayHardware();
-        const Region screenRegion(hw.bounds());
-        if (visibleRegions) {
+        if (visibleRegions || mVisibleRegionsDirty) {
             Region opaqueRegion;
             computeVisibleRegions(currentLayers, mDirtyRegion, opaqueRegion);
 
@@ -770,7 +784,7 @@ void SurfaceFlinger::unlockPageFlip(const LayerVector& currentLayers)
 {
     const GraphicPlane& plane(graphicPlane(0));
     const Transform& planeTransform(plane.transform());
-    size_t count = currentLayers.size();
+    const size_t count = currentLayers.size();
     sp<LayerBase> const* layers = currentLayers.array();
     for (size_t i=0 ; i<count ; i++) {
         const sp<LayerBase>& layer(layers[i]);
@@ -778,6 +792,23 @@ void SurfaceFlinger::unlockPageFlip(const LayerVector& currentLayers)
     }
 }
 
+void SurfaceFlinger::handleRefresh()
+{
+    bool needInvalidate = false;
+    const LayerVector& currentLayers(mDrawingState.layersSortedByZ);
+    const size_t count = currentLayers.size();
+    for (size_t i=0 ; i<count ; i++) {
+        const sp<LayerBase>& layer(currentLayers[i]);
+        if (layer->onPreComposition()) {
+            needInvalidate = true;
+        }
+    }
+    if (needInvalidate) {
+        signalLayerUpdate();
+    }
+}
+
+
 void SurfaceFlinger::handleWorkList()
 {
     mHwWorkListDirty = false;
@@ -1175,7 +1206,7 @@ uint32_t SurfaceFlinger::setTransactionFlags(uint32_t flags)
 {
     uint32_t old = android_atomic_or(flags, &mTransactionFlags);
     if ((old & flags)==0) { // wake the server up
-        signalEvent();
+        signalTransaction();
     }
     return old;
 }
@@ -1426,14 +1457,14 @@ void SurfaceFlinger::screenReleased(int dpy)
 {
     // this may be called by a signal handler, we can't do too much in here
     android_atomic_or(eConsoleReleased, &mConsoleSignals);
-    signalEvent();
+    signalTransaction();
 }
 
 void SurfaceFlinger::screenAcquired(int dpy)
 {
     // this may be called by a signal handler, we can't do too much in here
     android_atomic_or(eConsoleAcquired, &mConsoleSignals);
-    signalEvent();
+    signalTransaction();
 }
 
 status_t SurfaceFlinger::dump(int fd, const Vector<String16>& args)
@@ -1769,7 +1800,7 @@ void SurfaceFlinger::repaintEverything() {
     const DisplayHardware& hw(graphicPlane(0).displayHardware());
     const Rect bounds(hw.getBounds());
     setInvalidateRegion(Region(bounds));
-    signalEvent();
+    signalTransaction();
 }
 
 void SurfaceFlinger::setInvalidateRegion(const Region& reg) {
@@ -2245,7 +2276,7 @@ status_t SurfaceFlinger::turnElectronBeamOnImplLocked(int32_t mode)
 
     // make sure to redraw the whole screen when the animation is done
     mDirtyRegion.set(hw.bounds());
-    signalEvent();
+    signalTransaction();
 
     return NO_ERROR;
 }
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index c24a9de..fcd9361 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -190,6 +190,8 @@ public:
             status_t renderScreenToTextureLocked(DisplayID dpy,
                     GLuint* textureName, GLfloat* uOut, GLfloat* vOut);
 
+            void onMessageReceived(int32_t what);
+
             status_t postMessageAsync(const sp<MessageBase>& msg,
                     nsecs_t reltime=0, uint32_t flags = 0);
 
@@ -283,7 +285,10 @@ private:
 public:     // hack to work around gcc 4.0.3 bug
     const GraphicPlane&     graphicPlane(int dpy) const;
           GraphicPlane&     graphicPlane(int dpy);
-          void              signalEvent();
+
+          void              signalTransaction();
+          void              signalLayerUpdate();
+          void              signalRefresh();
           void              repaintEverything();
 
 private:
@@ -300,6 +305,7 @@ private:
             void        handlePageFlip();
             bool        lockPageFlip(const LayerVector& currentLayers);
             void        unlockPageFlip(const LayerVector& currentLayers);
+            void        handleRefresh();
             void        handleWorkList();
             void        handleRepaint();
             void        postFramebuffer();