diff --git a/services/surfaceflinger/Scheduler/MessageQueue.cpp b/services/surfaceflinger/Scheduler/MessageQueue.cpp
index 4d51125..043a536 100644
--- a/services/surfaceflinger/Scheduler/MessageQueue.cpp
+++ b/services/surfaceflinger/Scheduler/MessageQueue.cpp
@@ -27,49 +27,55 @@
 #include "EventThread.h"
 #include "FrameTimeline.h"
 #include "MessageQueue.h"
-#include "SurfaceFlinger.h"
 
 namespace android::impl {
 
-void MessageQueue::Handler::dispatchRefresh() {
-    if ((mEventMask.fetch_or(eventMaskRefresh) & eventMaskRefresh) == 0) {
-        mQueue.mLooper->sendMessage(this, Message(MessageQueue::REFRESH));
+void MessageQueue::Handler::dispatchComposite() {
+    if ((mEventMask.fetch_or(kComposite) & kComposite) == 0) {
+        mQueue.mLooper->sendMessage(this, Message(kComposite));
     }
 }
 
-void MessageQueue::Handler::dispatchInvalidate(int64_t vsyncId, nsecs_t expectedVSyncTimestamp) {
-    if ((mEventMask.fetch_or(eventMaskInvalidate) & eventMaskInvalidate) == 0) {
+void MessageQueue::Handler::dispatchCommit(int64_t vsyncId, nsecs_t expectedVsyncTime) {
+    if ((mEventMask.fetch_or(kCommit) & kCommit) == 0) {
         mVsyncId = vsyncId;
-        mExpectedVSyncTime = expectedVSyncTimestamp;
-        mQueue.mLooper->sendMessage(this, Message(MessageQueue::INVALIDATE));
+        mExpectedVsyncTime = expectedVsyncTime;
+        mQueue.mLooper->sendMessage(this, Message(kCommit));
     }
 }
 
-bool MessageQueue::Handler::invalidatePending() {
-    constexpr auto pendingMask = eventMaskInvalidate | eventMaskRefresh;
-    return (mEventMask.load() & pendingMask) != 0;
+bool MessageQueue::Handler::isFramePending() const {
+    constexpr auto kPendingMask = kCommit | kComposite;
+    return (mEventMask.load() & kPendingMask) != 0;
 }
 
 void MessageQueue::Handler::handleMessage(const Message& message) {
+    const nsecs_t frameTime = systemTime();
     switch (message.what) {
-        case INVALIDATE:
-            mEventMask.fetch_and(~eventMaskInvalidate);
-            mQueue.mFlinger->onMessageReceived(message.what, mVsyncId, mExpectedVSyncTime);
-            break;
-        case REFRESH:
-            mEventMask.fetch_and(~eventMaskRefresh);
-            mQueue.mFlinger->onMessageReceived(message.what, mVsyncId, mExpectedVSyncTime);
+        case kCommit:
+            mEventMask.fetch_and(~kCommit);
+            if (!mQueue.mCompositor.commit(frameTime, mVsyncId, mExpectedVsyncTime)) {
+                return;
+            }
+            // Composite immediately, rather than after pending tasks through scheduleComposite.
+            [[fallthrough]];
+        case kComposite:
+            mEventMask.fetch_and(~kComposite);
+            mQueue.mCompositor.composite(frameTime);
+            mQueue.mCompositor.sample();
             break;
     }
 }
 
-// ---------------------------------------------------------------------------
+MessageQueue::MessageQueue(ICompositor& compositor)
+      : MessageQueue(compositor, sp<Handler>::make(*this)) {}
 
-void MessageQueue::init(const sp<SurfaceFlinger>& flinger) {
-    mFlinger = flinger;
-    mLooper = new Looper(true);
-    mHandler = new Handler(*this);
-}
+constexpr bool kAllowNonCallbacks = true;
+
+MessageQueue::MessageQueue(ICompositor& compositor, sp<Handler> handler)
+      : mCompositor(compositor),
+        mLooper(sp<Looper>::make(kAllowNonCallbacks)),
+        mHandler(std::move(handler)) {}
 
 // TODO(b/169865816): refactor VSyncInjections to use MessageQueue directly
 // and remove the EventThread from MessageQueue
@@ -110,11 +116,13 @@
     {
         std::lock_guard lock(mVsync.mutex);
         mVsync.lastCallbackTime = std::chrono::nanoseconds(vsyncTime);
-        mVsync.scheduled = false;
+        mVsync.scheduledFrameTime.reset();
     }
-    mHandler->dispatchInvalidate(mVsync.tokenManager->generateTokenForPredictions(
-                                         {targetWakeupTime, readyTime, vsyncTime}),
-                                 vsyncTime);
+
+    const auto vsyncId = mVsync.tokenManager->generateTokenForPredictions(
+            {targetWakeupTime, readyTime, vsyncTime});
+
+    mHandler->dispatchCommit(vsyncId, vsyncTime);
 }
 
 void MessageQueue::initVsync(scheduler::VSyncDispatch& dispatch,
@@ -135,8 +143,8 @@
     ATRACE_CALL();
     std::lock_guard lock(mVsync.mutex);
     mVsync.workDuration = workDuration;
-    if (mVsync.scheduled) {
-        mVsync.expectedWakeupTime = mVsync.registration->schedule(
+    if (mVsync.scheduledFrameTime) {
+        mVsync.scheduledFrameTime = mVsync.registration->schedule(
                 {mVsync.workDuration.get().count(),
                  /*readyDuration=*/0, mVsync.lastCallbackTime.count()});
     }
@@ -168,7 +176,7 @@
     mLooper->sendMessage(handler, Message());
 }
 
-void MessageQueue::invalidate() {
+void MessageQueue::scheduleCommit() {
     ATRACE_CALL();
 
     {
@@ -181,15 +189,14 @@
     }
 
     std::lock_guard lock(mVsync.mutex);
-    mVsync.scheduled = true;
-    mVsync.expectedWakeupTime =
+    mVsync.scheduledFrameTime =
             mVsync.registration->schedule({.workDuration = mVsync.workDuration.get().count(),
                                            .readyDuration = 0,
                                            .earliestVsync = mVsync.lastCallbackTime.count()});
 }
 
-void MessageQueue::refresh() {
-    mHandler->dispatchRefresh();
+void MessageQueue::scheduleComposite() {
+    mHandler->dispatchComposite();
 }
 
 void MessageQueue::injectorCallback() {
@@ -198,24 +205,22 @@
     while ((n = DisplayEventReceiver::getEvents(&mInjector.tube, buffer, 8)) > 0) {
         for (int i = 0; i < n; i++) {
             if (buffer[i].header.type == DisplayEventReceiver::DISPLAY_EVENT_VSYNC) {
-                mHandler->dispatchInvalidate(buffer[i].vsync.vsyncId,
-                                             buffer[i].vsync.expectedVSyncTimestamp);
+                mHandler->dispatchCommit(buffer[i].vsync.vsyncId,
+                                         buffer[i].vsync.expectedVSyncTimestamp);
                 break;
             }
         }
     }
 }
 
-std::optional<std::chrono::steady_clock::time_point> MessageQueue::nextExpectedInvalidate() {
-    if (mHandler->invalidatePending()) {
-        return std::chrono::steady_clock::now();
+auto MessageQueue::getScheduledFrameTime() const -> std::optional<Clock::time_point> {
+    if (mHandler->isFramePending()) {
+        return Clock::now();
     }
 
     std::lock_guard lock(mVsync.mutex);
-    if (mVsync.scheduled) {
-        LOG_ALWAYS_FATAL_IF(!mVsync.expectedWakeupTime.has_value(), "callback was never scheduled");
-        const auto expectedWakeupTime = std::chrono::nanoseconds(*mVsync.expectedWakeupTime);
-        return std::optional<std::chrono::steady_clock::time_point>(expectedWakeupTime);
+    if (const auto time = mVsync.scheduledFrameTime) {
+        return Clock::time_point(std::chrono::nanoseconds(*time));
     }
 
     return std::nullopt;
diff --git a/services/surfaceflinger/Scheduler/MessageQueue.h b/services/surfaceflinger/Scheduler/MessageQueue.h
index 58ce9b9..2c908a6 100644
--- a/services/surfaceflinger/Scheduler/MessageQueue.h
+++ b/services/surfaceflinger/Scheduler/MessageQueue.h
@@ -33,7 +33,14 @@
 
 namespace android {
 
-class SurfaceFlinger;
+struct ICompositor {
+    virtual bool commit(nsecs_t frameTime, int64_t vsyncId, nsecs_t expectedVsyncTime) = 0;
+    virtual void composite(nsecs_t frameTime) = 0;
+    virtual void sample() = 0;
+
+protected:
+    ~ICompositor() = default;
+};
 
 template <typename F>
 class Task : public MessageHandler {
@@ -56,65 +63,65 @@
 
 class MessageQueue {
 public:
-    enum {
-        INVALIDATE = 0,
-        REFRESH = 1,
-    };
-
     virtual ~MessageQueue() = default;
 
-    virtual void init(const sp<SurfaceFlinger>& flinger) = 0;
     virtual void initVsync(scheduler::VSyncDispatch&, frametimeline::TokenManager&,
                            std::chrono::nanoseconds workDuration) = 0;
     virtual void setDuration(std::chrono::nanoseconds workDuration) = 0;
     virtual void setInjector(sp<EventThreadConnection>) = 0;
     virtual void waitMessage() = 0;
     virtual void postMessage(sp<MessageHandler>&&) = 0;
-    virtual void invalidate() = 0;
-    virtual void refresh() = 0;
-    virtual std::optional<std::chrono::steady_clock::time_point> nextExpectedInvalidate() = 0;
-};
+    virtual void scheduleCommit() = 0;
+    virtual void scheduleComposite() = 0;
 
-// ---------------------------------------------------------------------------
+    using Clock = std::chrono::steady_clock;
+    virtual std::optional<Clock::time_point> getScheduledFrameTime() const = 0;
+};
 
 namespace impl {
 
 class MessageQueue : public android::MessageQueue {
 protected:
     class Handler : public MessageHandler {
-        enum : uint32_t {
-            eventMaskInvalidate = 0x1,
-            eventMaskRefresh = 0x2,
-            eventMaskTransaction = 0x4
-        };
+        static constexpr uint32_t kCommit = 0b1;
+        static constexpr uint32_t kComposite = 0b10;
+
         MessageQueue& mQueue;
-        std::atomic<uint32_t> mEventMask;
-        std::atomic<int64_t> mVsyncId;
-        std::atomic<nsecs_t> mExpectedVSyncTime;
+        std::atomic<uint32_t> mEventMask = 0;
+        std::atomic<int64_t> mVsyncId = 0;
+        std::atomic<nsecs_t> mExpectedVsyncTime = 0;
 
     public:
-        explicit Handler(MessageQueue& queue) : mQueue(queue), mEventMask(0) {}
+        explicit Handler(MessageQueue& queue) : mQueue(queue) {}
         void handleMessage(const Message& message) override;
-        virtual void dispatchRefresh();
-        virtual void dispatchInvalidate(int64_t vsyncId, nsecs_t expectedVSyncTimestamp);
-        virtual bool invalidatePending();
+
+        bool isFramePending() const;
+
+        virtual void dispatchCommit(int64_t vsyncId, nsecs_t expectedVsyncTime);
+        void dispatchComposite();
     };
 
     friend class Handler;
 
-    sp<SurfaceFlinger> mFlinger;
-    sp<Looper> mLooper;
+    // For tests.
+    MessageQueue(ICompositor&, sp<Handler>);
+
+    void vsyncCallback(nsecs_t vsyncTime, nsecs_t targetWakeupTime, nsecs_t readyTime);
+
+private:
+    ICompositor& mCompositor;
+    const sp<Looper> mLooper;
+    const sp<Handler> mHandler;
 
     struct Vsync {
         frametimeline::TokenManager* tokenManager = nullptr;
         std::unique_ptr<scheduler::VSyncCallbackRegistration> registration;
 
-        std::mutex mutex;
+        mutable std::mutex mutex;
         TracedOrdinal<std::chrono::nanoseconds> workDuration
                 GUARDED_BY(mutex) = {"VsyncWorkDuration-sf", std::chrono::nanoseconds(0)};
         std::chrono::nanoseconds lastCallbackTime GUARDED_BY(mutex) = std::chrono::nanoseconds{0};
-        bool scheduled GUARDED_BY(mutex) = false;
-        std::optional<nsecs_t> expectedWakeupTime GUARDED_BY(mutex);
+        std::optional<nsecs_t> scheduledFrameTime GUARDED_BY(mutex);
         TracedOrdinal<int> value = {"VSYNC-sf", 0};
     };
 
@@ -127,14 +134,11 @@
     Vsync mVsync;
     Injector mInjector;
 
-    sp<Handler> mHandler;
-
-    void vsyncCallback(nsecs_t vsyncTime, nsecs_t targetWakeupTime, nsecs_t readyTime);
     void injectorCallback();
 
 public:
-    ~MessageQueue() override = default;
-    void init(const sp<SurfaceFlinger>& flinger) override;
+    explicit MessageQueue(ICompositor&);
+
     void initVsync(scheduler::VSyncDispatch&, frametimeline::TokenManager&,
                    std::chrono::nanoseconds workDuration) override;
     void setDuration(std::chrono::nanoseconds workDuration) override;
@@ -143,13 +147,10 @@
     void waitMessage() override;
     void postMessage(sp<MessageHandler>&&) override;
 
-    // sends INVALIDATE message at next VSYNC
-    void invalidate() override;
+    void scheduleCommit() override;
+    void scheduleComposite() override;
 
-    // sends REFRESH message at next VSYNC
-    void refresh() override;
-
-    std::optional<std::chrono::steady_clock::time_point> nextExpectedInvalidate() override;
+    std::optional<Clock::time_point> getScheduledFrameTime() const override;
 };
 
 } // namespace impl
diff --git a/services/surfaceflinger/Scheduler/Scheduler.cpp b/services/surfaceflinger/Scheduler/Scheduler.cpp
index 12e741b..c6a19de 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.cpp
+++ b/services/surfaceflinger/Scheduler/Scheduler.cpp
@@ -870,7 +870,7 @@
 
 void Scheduler::onNewVsyncPeriodChangeTimeline(const hal::VsyncPeriodChangeTimeline& timeline) {
     if (timeline.refreshRequired) {
-        mSchedulerCallback.scheduleRefresh(FrameHint::kNone);
+        mSchedulerCallback.scheduleComposite(FrameHint::kNone);
     }
 
     std::lock_guard<std::mutex> lock(mVsyncTimelineLock);
@@ -882,12 +882,12 @@
     }
 }
 
-void Scheduler::onDisplayRefreshed(nsecs_t timestamp) {
-    const bool refresh = [=] {
+void Scheduler::onPostComposition(nsecs_t presentTime) {
+    const bool recomposite = [=] {
         std::lock_guard<std::mutex> lock(mVsyncTimelineLock);
         if (mLastVsyncPeriodChangeTimeline && mLastVsyncPeriodChangeTimeline->refreshRequired) {
-            if (timestamp < mLastVsyncPeriodChangeTimeline->refreshTimeNanos) {
-                // We need to schedule another refresh as refreshTimeNanos is still in the future.
+            if (presentTime < mLastVsyncPeriodChangeTimeline->refreshTimeNanos) {
+                // We need to composite again as refreshTimeNanos is still in the future.
                 return true;
             }
 
@@ -896,8 +896,8 @@
         return false;
     }();
 
-    if (refresh) {
-        mSchedulerCallback.scheduleRefresh(FrameHint::kNone);
+    if (recomposite) {
+        mSchedulerCallback.scheduleComposite(FrameHint::kNone);
     }
 }
 
diff --git a/services/surfaceflinger/Scheduler/Scheduler.h b/services/surfaceflinger/Scheduler/Scheduler.h
index 3f3debe..0a33dbb 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.h
+++ b/services/surfaceflinger/Scheduler/Scheduler.h
@@ -59,7 +59,7 @@
     // Indicates frame activity, i.e. whether commit and/or composite is taking place.
     enum class FrameHint { kNone, kActive };
 
-    virtual void scheduleRefresh(FrameHint) = 0;
+    virtual void scheduleComposite(FrameHint) = 0;
     virtual void setVsyncEnabled(bool) = 0;
     virtual void changeRefreshRate(const scheduler::RefreshRateConfigs::RefreshRate&,
                                    scheduler::RefreshRateConfigEvent) = 0;
@@ -162,8 +162,8 @@
     // Notifies the scheduler about a refresh rate timeline change.
     void onNewVsyncPeriodChangeTimeline(const hal::VsyncPeriodChangeTimeline& timeline);
 
-    // Notifies the scheduler when the display was refreshed
-    void onDisplayRefreshed(nsecs_t timestamp);
+    // Notifies the scheduler post composition.
+    void onPostComposition(nsecs_t presentTime);
 
     // Notifies the scheduler when the display size has changed. Called from SF's main thread
     void onActiveDisplayAreaChanged(uint32_t displayArea);