Rename "leader" display to "pacesetter"

"Leader" became ambiguous once we began to consider that there are two
orthogonal concepts that "leader" seems to imply:
- The display with the highest refresh rate (originally called "leader")
- The display that is refreshed first in a given update (assuming it's
  being updated)

To better distinguish between the two, we've come up with new names:
- pacesetter
- front runner (for the second concept)

Change uses of "leader" to "pacesetter" throughout SF and Scheduler.

Bug: 255635821
Bug: 256196556
Test: m
Change-Id: Ia02c35dd442d310695f1ce873fbaf30910c12419
diff --git a/services/surfaceflinger/Scheduler/Scheduler.cpp b/services/surfaceflinger/Scheduler/Scheduler.cpp
index 064f853..bc3a1a0 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.cpp
+++ b/services/surfaceflinger/Scheduler/Scheduler.cpp
@@ -81,7 +81,7 @@
     mTouchTimer.reset();
 
     // Stop idle timer and clear callbacks, as the RefreshRateSelector may outlive the Scheduler.
-    demoteLeaderDisplay();
+    demotePacesetterDisplay();
 }
 
 void Scheduler::startTimers() {
@@ -106,11 +106,11 @@
     }
 }
 
-void Scheduler::setLeaderDisplay(std::optional<PhysicalDisplayId> leaderIdOpt) {
-    demoteLeaderDisplay();
+void Scheduler::setPacesetterDisplay(std::optional<PhysicalDisplayId> pacesetterIdOpt) {
+    demotePacesetterDisplay();
 
     std::scoped_lock lock(mDisplayLock);
-    promoteLeaderDisplay(leaderIdOpt);
+    promotePacesetterDisplay(pacesetterIdOpt);
 }
 
 void Scheduler::registerDisplay(PhysicalDisplayId displayId, RefreshRateSelectorPtr selectorPtr) {
@@ -121,17 +121,17 @@
 void Scheduler::registerDisplayInternal(PhysicalDisplayId displayId,
                                         RefreshRateSelectorPtr selectorPtr,
                                         std::shared_ptr<VsyncSchedule> vsyncSchedule) {
-    demoteLeaderDisplay();
+    demotePacesetterDisplay();
 
     std::scoped_lock lock(mDisplayLock);
     mRefreshRateSelectors.emplace_or_replace(displayId, std::move(selectorPtr));
     mVsyncSchedules.emplace_or_replace(displayId, std::move(vsyncSchedule));
 
-    promoteLeaderDisplay();
+    promotePacesetterDisplay();
 }
 
 void Scheduler::unregisterDisplay(PhysicalDisplayId displayId) {
-    demoteLeaderDisplay();
+    demotePacesetterDisplay();
 
     std::scoped_lock lock(mDisplayLock);
     mRefreshRateSelectors.erase(displayId);
@@ -142,7 +142,7 @@
     // headless virtual display.)
     LOG_ALWAYS_FATAL_IF(mRefreshRateSelectors.empty(), "Cannot unregister all displays!");
 
-    promoteLeaderDisplay();
+    promotePacesetterDisplay();
 }
 
 void Scheduler::run() {
@@ -165,7 +165,7 @@
 
 std::optional<Fps> Scheduler::getFrameRateOverride(uid_t uid) const {
     const bool supportsFrameRateOverrideByContent =
-            leaderSelectorPtr()->supportsAppFrameRateOverrideByContent();
+            pacesetterSelectorPtr()->supportsAppFrameRateOverrideByContent();
     return mFrameRateOverrideMappings
             .getFrameRateOverrideForUid(uid, supportsFrameRateOverrideByContent);
 }
@@ -192,7 +192,7 @@
 
 impl::EventThread::GetVsyncPeriodFunction Scheduler::makeGetVsyncPeriodFunction() const {
     return [this](uid_t uid) {
-        const Fps refreshRate = leaderSelectorPtr()->getActiveMode().fps;
+        const Fps refreshRate = pacesetterSelectorPtr()->getActiveMode().fps;
         const nsecs_t currentPeriod =
                 getVsyncSchedule()->period().ns() ?: refreshRate.getPeriodNsecs();
 
@@ -285,7 +285,7 @@
 
 void Scheduler::onFrameRateOverridesChanged(ConnectionHandle handle, PhysicalDisplayId displayId) {
     const bool supportsFrameRateOverrideByContent =
-            leaderSelectorPtr()->supportsAppFrameRateOverrideByContent();
+            pacesetterSelectorPtr()->supportsAppFrameRateOverrideByContent();
 
     std::vector<FrameRateOverride> overrides =
             mFrameRateOverrideMappings.getAllFrameRateOverrides(supportsFrameRateOverrideByContent);
@@ -326,7 +326,7 @@
     // If the mode is not the current mode, this means that a
     // mode change is in progress. In that case we shouldn't dispatch an event
     // as it will be dispatched when the current mode changes.
-    if (leaderSelectorPtr()->getActiveMode() != mPolicy.modeOpt) {
+    if (pacesetterSelectorPtr()->getActiveMode() != mPolicy.modeOpt) {
         return;
     }
 
@@ -489,7 +489,7 @@
 
 void Scheduler::recordLayerHistory(Layer* layer, nsecs_t presentTime,
                                    LayerHistory::LayerUpdateType updateType) {
-    if (leaderSelectorPtr()->canSwitch()) {
+    if (pacesetterSelectorPtr()->canSwitch()) {
         mLayerHistory.record(layer, presentTime, systemTime(), updateType);
     }
 }
@@ -504,7 +504,7 @@
 }
 
 void Scheduler::chooseRefreshRateForContent() {
-    const auto selectorPtr = leaderSelectorPtr();
+    const auto selectorPtr = pacesetterSelectorPtr();
     if (!selectorPtr->canSwitch()) return;
 
     ATRACE_CALL();
@@ -514,22 +514,22 @@
 }
 
 void Scheduler::resetIdleTimer() {
-    leaderSelectorPtr()->resetIdleTimer();
+    pacesetterSelectorPtr()->resetIdleTimer();
 }
 
 void Scheduler::onTouchHint() {
     if (mTouchTimer) {
         mTouchTimer->reset();
-        leaderSelectorPtr()->resetKernelIdleTimer();
+        pacesetterSelectorPtr()->resetKernelIdleTimer();
     }
 }
 
 void Scheduler::setDisplayPowerMode(PhysicalDisplayId id, hal::PowerMode powerMode) {
-    const bool isLeader = [this, id]() REQUIRES(kMainThreadContext) {
+    const bool isPacesetter = [this, id]() REQUIRES(kMainThreadContext) {
         ftl::FakeGuard guard(mDisplayLock);
-        return id == mLeaderDisplayId;
+        return id == mPacesetterDisplayId;
     }();
-    if (isLeader) {
+    if (isPacesetter) {
         // TODO (b/255657128): This needs to be handled per display.
         std::lock_guard<std::mutex> lock(mPolicyLock);
         mPolicy.displayPowerMode = powerMode;
@@ -539,7 +539,7 @@
         auto vsyncSchedule = getVsyncScheduleLocked(id);
         vsyncSchedule->getController().setDisplayPowerMode(powerMode);
     }
-    if (!isLeader) return;
+    if (!isPacesetter) return;
 
     if (mDisplayPowerTimer) {
         mDisplayPowerTimer->reset();
@@ -560,8 +560,8 @@
         std::optional<PhysicalDisplayId> idOpt) const {
     ftl::FakeGuard guard(kMainThreadContext);
     if (!idOpt) {
-        LOG_ALWAYS_FATAL_IF(!mLeaderDisplayId, "Missing a leader!");
-        idOpt = mLeaderDisplayId;
+        LOG_ALWAYS_FATAL_IF(!mPacesetterDisplayId, "Missing a pacesetter!");
+        idOpt = mPacesetterDisplayId;
     }
     auto scheduleOpt = mVsyncSchedules.get(*idOpt);
     LOG_ALWAYS_FATAL_IF(!scheduleOpt);
@@ -573,7 +573,7 @@
 
     // TODO(145561154): cleanup the kernel idle timer implementation and the refresh rate
     // magic number
-    const Fps refreshRate = leaderSelectorPtr()->getActiveMode().modePtr->getFps();
+    const Fps refreshRate = pacesetterSelectorPtr()->getActiveMode().modePtr->getFps();
 
     constexpr Fps FPS_THRESHOLD_FOR_KERNEL_TIMER = 65_Hz;
     using namespace fps_approx_ops;
@@ -637,7 +637,7 @@
         {
             std::scoped_lock lock(mDisplayLock);
             ftl::FakeGuard guard(kMainThreadContext);
-            dumper.dump("leaderDisplayId"sv, mLeaderDisplayId);
+            dumper.dump("pacesetterDisplayId"sv, mPacesetterDisplayId);
         }
         dumper.dump("layerHistory"sv, mLayerHistory.dump());
         dumper.dump("touchTimer"sv, mTouchTimer.transform(&OneShotTimer::interval));
@@ -651,13 +651,13 @@
 void Scheduler::dumpVsync(std::string& out) const {
     std::scoped_lock lock(mDisplayLock);
     ftl::FakeGuard guard(kMainThreadContext);
-    if (mLeaderDisplayId) {
-        base::StringAppendF(&out, "VsyncSchedule for leader %s:\n",
-                            to_string(*mLeaderDisplayId).c_str());
+    if (mPacesetterDisplayId) {
+        base::StringAppendF(&out, "VsyncSchedule for pacesetter %s:\n",
+                            to_string(*mPacesetterDisplayId).c_str());
         getVsyncScheduleLocked()->dump(out);
     }
     for (auto& [id, vsyncSchedule] : mVsyncSchedules) {
-        if (id == mLeaderDisplayId) {
+        if (id == mPacesetterDisplayId) {
             continue;
         }
         base::StringAppendF(&out, "VsyncSchedule for follower %s:\n", to_string(id).c_str());
@@ -669,31 +669,31 @@
     if (consideredSignals.idle) return false;
 
     const auto frameRateOverrides =
-            leaderSelectorPtr()->getFrameRateOverrides(mPolicy.contentRequirements,
-                                                       displayRefreshRate, consideredSignals);
+            pacesetterSelectorPtr()->getFrameRateOverrides(mPolicy.contentRequirements,
+                                                           displayRefreshRate, consideredSignals);
 
     // Note that RefreshRateSelector::supportsFrameRateOverrideByContent is checked when querying
     // the FrameRateOverrideMappings rather than here.
     return mFrameRateOverrideMappings.updateFrameRateOverridesByContent(frameRateOverrides);
 }
 
-void Scheduler::promoteLeaderDisplay(std::optional<PhysicalDisplayId> leaderIdOpt) {
-    // TODO(b/241286431): Choose the leader display.
-    mLeaderDisplayId = leaderIdOpt.value_or(mRefreshRateSelectors.begin()->first);
-    ALOGI("Display %s is the leader", to_string(*mLeaderDisplayId).c_str());
+void Scheduler::promotePacesetterDisplay(std::optional<PhysicalDisplayId> pacesetterIdOpt) {
+    // TODO(b/241286431): Choose the pacesetter display.
+    mPacesetterDisplayId = pacesetterIdOpt.value_or(mRefreshRateSelectors.begin()->first);
+    ALOGI("Display %s is the pacesetter", to_string(*mPacesetterDisplayId).c_str());
 
-    auto vsyncSchedule = getVsyncScheduleLocked(*mLeaderDisplayId);
-    if (const auto leaderPtr = leaderSelectorPtrLocked()) {
-        leaderPtr->setIdleTimerCallbacks(
+    auto vsyncSchedule = getVsyncScheduleLocked(*mPacesetterDisplayId);
+    if (const auto pacesetterPtr = pacesetterSelectorPtrLocked()) {
+        pacesetterPtr->setIdleTimerCallbacks(
                 {.platform = {.onReset = [this] { idleTimerCallback(TimerState::Reset); },
                               .onExpired = [this] { idleTimerCallback(TimerState::Expired); }},
                  .kernel = {.onReset = [this] { kernelIdleTimerCallback(TimerState::Reset); },
                             .onExpired =
                                     [this] { kernelIdleTimerCallback(TimerState::Expired); }}});
 
-        leaderPtr->startIdleTimer();
+        pacesetterPtr->startIdleTimer();
 
-        const Fps refreshRate = leaderPtr->getActiveMode().modePtr->getFps();
+        const Fps refreshRate = pacesetterPtr->getActiveMode().modePtr->getFps();
         vsyncSchedule->startPeriodTransition(mSchedulerCallback, refreshRate.getPeriod(),
                                              true /* force */);
     }
@@ -707,14 +707,14 @@
     }
 }
 
-void Scheduler::demoteLeaderDisplay() {
+void Scheduler::demotePacesetterDisplay() {
     // No need to lock for reads on kMainThreadContext.
-    if (const auto leaderPtr = FTL_FAKE_GUARD(mDisplayLock, leaderSelectorPtrLocked())) {
-        leaderPtr->stopIdleTimer();
-        leaderPtr->clearIdleTimerCallbacks();
+    if (const auto pacesetterPtr = FTL_FAKE_GUARD(mDisplayLock, pacesetterSelectorPtrLocked())) {
+        pacesetterPtr->stopIdleTimer();
+        pacesetterPtr->clearIdleTimerCallbacks();
     }
 
-    // Clear state that depends on the leader's RefreshRateSelector.
+    // Clear state that depends on the pacesetter's RefreshRateSelector.
     std::scoped_lock lock(mPolicyLock);
     mPolicy = {};
 }
@@ -743,10 +743,11 @@
 
             modeChoices = chooseDisplayModes();
 
-            // TODO(b/240743786): The leader display's mode must change for any DisplayModeRequest
-            // to go through. Fix this by tracking per-display Scheduler::Policy and timers.
+            // TODO(b/240743786): The pacesetter display's mode must change for any
+            // DisplayModeRequest to go through. Fix this by tracking per-display Scheduler::Policy
+            // and timers.
             std::tie(modeOpt, consideredSignals) =
-                    modeChoices.get(*mLeaderDisplayId)
+                    modeChoices.get(*mPacesetterDisplayId)
                             .transform([](const DisplayModeChoice& choice) {
                                 return std::make_pair(choice.mode, choice.consideredSignals);
                             })
@@ -879,7 +880,7 @@
 FrameRateMode Scheduler::getPreferredDisplayMode() {
     std::lock_guard<std::mutex> lock(mPolicyLock);
     const auto frameRateMode =
-            leaderSelectorPtr()
+            pacesetterSelectorPtr()
                     ->getRankedFrameRates(mPolicy.contentRequirements, makeGlobalSignals())
                     .ranking.front()
                     .frameRateMode;
diff --git a/services/surfaceflinger/Scheduler/Scheduler.h b/services/surfaceflinger/Scheduler/Scheduler.h
index 7374054..3e93ef4 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.h
+++ b/services/surfaceflinger/Scheduler/Scheduler.h
@@ -102,8 +102,8 @@
 
     void startTimers();
 
-    // TODO(b/241285191): Remove this API by promoting leader in onScreen{Acquired,Released}.
-    void setLeaderDisplay(std::optional<PhysicalDisplayId>) REQUIRES(kMainThreadContext)
+    // TODO(b/241285191): Remove this API by promoting pacesetter in onScreen{Acquired,Released}.
+    void setPacesetterDisplay(std::optional<PhysicalDisplayId>) REQUIRES(kMainThreadContext)
             EXCLUDES(mDisplayLock);
 
     using RefreshRateSelectorPtr = std::shared_ptr<RefreshRateSelector>;
@@ -167,9 +167,9 @@
 
     const VsyncModulator& vsyncModulator() const { return *mVsyncModulator; }
 
-    // In some cases, we should only modulate for the leader display. In those
+    // In some cases, we should only modulate for the pacesetter display. In those
     // cases, the caller should pass in the relevant display, and the method
-    // will no-op if it's not the leader. Other cases are not specific to a
+    // will no-op if it's not the pacesetter. Other cases are not specific to a
     // display.
     template <typename... Args,
               typename Handler = std::optional<VsyncConfig> (VsyncModulator::*)(Args...)>
@@ -177,13 +177,13 @@
         if (id) {
             std::scoped_lock lock(mDisplayLock);
             ftl::FakeGuard guard(kMainThreadContext);
-            if (id != mLeaderDisplayId) {
+            if (id != mPacesetterDisplayId) {
                 return;
             }
         }
 
         if (const auto config = (*mVsyncModulator.*handler)(args...)) {
-            setVsyncConfig(*config, getLeaderVsyncPeriod());
+            setVsyncConfig(*config, getPacesetterVsyncPeriod());
         }
     }
 
@@ -254,7 +254,7 @@
     void dump(ConnectionHandle, std::string&) const;
     void dumpVsync(std::string&) const EXCLUDES(mDisplayLock);
 
-    // Returns the preferred refresh rate and frame rate for the leader display.
+    // Returns the preferred refresh rate and frame rate for the pacesetter display.
     FrameRateMode getPreferredDisplayMode();
 
     // Notifies the scheduler about a refresh rate timeline change.
@@ -277,12 +277,12 @@
     // Retrieves the overridden refresh rate for a given uid.
     std::optional<Fps> getFrameRateOverride(uid_t) const EXCLUDES(mDisplayLock);
 
-    Period getLeaderVsyncPeriod() const EXCLUDES(mDisplayLock) {
-        return leaderSelectorPtr()->getActiveMode().fps.getPeriod();
+    Period getPacesetterVsyncPeriod() const EXCLUDES(mDisplayLock) {
+        return pacesetterSelectorPtr()->getActiveMode().fps.getPeriod();
     }
 
-    Fps getLeaderRefreshRate() const EXCLUDES(mDisplayLock) {
-        return leaderSelectorPtr()->getActiveMode().fps;
+    Fps getPacesetterRefreshRate() const EXCLUDES(mDisplayLock) {
+        return pacesetterSelectorPtr()->getActiveMode().fps;
     }
 
     // Returns the framerate of the layer with the given sequence ID
@@ -318,14 +318,14 @@
     void resyncAllToHardwareVsync(bool allowToEnable) EXCLUDES(mDisplayLock);
     void setVsyncConfig(const VsyncConfig&, Period vsyncPeriod);
 
-    // Chooses a leader among the registered displays, unless `leaderIdOpt` is specified. The new
-    // `mLeaderDisplayId` is never `std::nullopt`.
-    void promoteLeaderDisplay(std::optional<PhysicalDisplayId> leaderIdOpt = std::nullopt)
+    // Chooses a pacesetter among the registered displays, unless `pacesetterIdOpt` is specified.
+    // The new `mPacesetterDisplayId` is never `std::nullopt`.
+    void promotePacesetterDisplay(std::optional<PhysicalDisplayId> pacesetterIdOpt = std::nullopt)
             REQUIRES(kMainThreadContext, mDisplayLock);
 
-    // Blocks until the leader's idle timer thread exits. `mDisplayLock` must not be locked by the
-    // caller on the main thread to avoid deadlock, since the timer thread locks it before exit.
-    void demoteLeaderDisplay() REQUIRES(kMainThreadContext) EXCLUDES(mDisplayLock, mPolicyLock);
+    // Blocks until the pacesetter's idle timer thread exits. `mDisplayLock` must not be locked by
+    // the caller on the main thread to avoid deadlock, since the timer thread locks it before exit.
+    void demotePacesetterDisplay() REQUIRES(kMainThreadContext) EXCLUDES(mDisplayLock, mPolicyLock);
 
     void registerDisplayInternal(PhysicalDisplayId, RefreshRateSelectorPtr,
                                  std::shared_ptr<VsyncSchedule>) REQUIRES(kMainThreadContext)
@@ -415,23 +415,23 @@
     display::PhysicalDisplayMap<PhysicalDisplayId, std::shared_ptr<VsyncSchedule>> mVsyncSchedules
             GUARDED_BY(mDisplayLock) GUARDED_BY(kMainThreadContext);
 
-    ftl::Optional<PhysicalDisplayId> mLeaderDisplayId GUARDED_BY(mDisplayLock)
+    ftl::Optional<PhysicalDisplayId> mPacesetterDisplayId GUARDED_BY(mDisplayLock)
             GUARDED_BY(kMainThreadContext);
 
-    RefreshRateSelectorPtr leaderSelectorPtr() const EXCLUDES(mDisplayLock) {
+    RefreshRateSelectorPtr pacesetterSelectorPtr() const EXCLUDES(mDisplayLock) {
         std::scoped_lock lock(mDisplayLock);
-        return leaderSelectorPtrLocked();
+        return pacesetterSelectorPtrLocked();
     }
 
-    RefreshRateSelectorPtr leaderSelectorPtrLocked() const REQUIRES(mDisplayLock) {
+    RefreshRateSelectorPtr pacesetterSelectorPtrLocked() const REQUIRES(mDisplayLock) {
         ftl::FakeGuard guard(kMainThreadContext);
-        const RefreshRateSelectorPtr noLeader;
-        return mLeaderDisplayId
-                .and_then([this](PhysicalDisplayId leaderId)
+        const RefreshRateSelectorPtr noPacesetter;
+        return mPacesetterDisplayId
+                .and_then([this](PhysicalDisplayId pacesetterId)
                                   REQUIRES(mDisplayLock, kMainThreadContext) {
-                                      return mRefreshRateSelectors.get(leaderId);
+                                      return mRefreshRateSelectors.get(pacesetterId);
                                   })
-                .value_or(std::cref(noLeader));
+                .value_or(std::cref(noPacesetter));
     }
 
     std::shared_ptr<const VsyncSchedule> getVsyncScheduleLocked(