From 755dd5818cb20a3b62cfc2a7c58e9dc209979540 Mon Sep 17 00:00:00 2001
From: Rupesh Bansal <brup@google.com>
Date: Fri, 15 Nov 2024 13:37:16 +0000
Subject: Subscribing viewroot impl to only display state changes

Bug: 379250246
Test: Manually verified the callbacks are received only on display state
changes
Flag: com.android.server.display.feature.flags.subscribe_granular_display_events

Change-Id: I85539fb9fe6e5873b671ae667a17e7978752bf97
---
 core/java/android/view/ViewRootImpl.java               | 18 +++++++++++++++---
 .../server/display/feature/DisplayManagerFlags.java    | 13 +++++++++++++
 .../server/display/feature/display_flags.aconfig       | 11 +++++++++++
 3 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/core/java/android/view/ViewRootImpl.java b/core/java/android/view/ViewRootImpl.java
index 19d3dc4df04e..00a0e1dfe907 100644
--- a/core/java/android/view/ViewRootImpl.java
+++ b/core/java/android/view/ViewRootImpl.java
@@ -1237,6 +1237,8 @@ public final class ViewRootImpl implements ViewParent,
     private @ActivityInfo.ColorMode int mCurrentColorMode = ActivityInfo.COLOR_MODE_DEFAULT;
     private long mColorModeLastSetMillis = -1;
 
+    private final boolean mIsSubscribeGranularDisplayEventsEnabled;
+
     public ViewRootImpl(Context context, Display display) {
         this(context, display, WindowManagerGlobal.getWindowSession(), new WindowLayout());
     }
@@ -1334,6 +1336,8 @@ public final class ViewRootImpl implements ViewParent,
         // Disable DRAW_WAKE_LOCK starting U.
         mDisableDrawWakeLock =
                 CompatChanges.isChangeEnabled(DISABLE_DRAW_WAKE_LOCK) && disableDrawWakeLock();
+        mIsSubscribeGranularDisplayEventsEnabled =
+                com.android.server.display.feature.flags.Flags.subscribeGranularDisplayEvents();
     }
 
     public static void addFirstDrawHandler(Runnable callback) {
@@ -1811,14 +1815,22 @@ public final class ViewRootImpl implements ViewParent,
                 mAccessibilityInteractionConnectionManager, mHandler);
         mAccessibilityManager.addHighContrastTextStateChangeListener(
                 mExecutor, mHighContrastTextManager);
+
+
+        long eventsToBeRegistered =
+                (mIsSubscribeGranularDisplayEventsEnabled)
+                ? DisplayManagerGlobal.INTERNAL_EVENT_FLAG_DISPLAY_ADDED
+                        | DisplayManagerGlobal.INTERNAL_EVENT_FLAG_DISPLAY_STATE
+                        | DisplayManagerGlobal.INTERNAL_EVENT_FLAG_DISPLAY_REMOVED
+                : DisplayManagerGlobal.INTERNAL_EVENT_FLAG_DISPLAY_ADDED
+                        | DisplayManagerGlobal.INTERNAL_EVENT_FLAG_DISPLAY_CHANGED
+                        | DisplayManagerGlobal.INTERNAL_EVENT_FLAG_DISPLAY_REMOVED;
         DisplayManagerGlobal
                 .getInstance()
                 .registerDisplayListener(
                         mDisplayListener,
                         mHandler,
-                        DisplayManagerGlobal.INTERNAL_EVENT_FLAG_DISPLAY_ADDED
-                        | DisplayManagerGlobal.INTERNAL_EVENT_FLAG_DISPLAY_CHANGED
-                        | DisplayManagerGlobal.INTERNAL_EVENT_FLAG_DISPLAY_REMOVED,
+                        eventsToBeRegistered,
                         mBasePackageName);
 
         if (forceInvertColor()) {
diff --git a/services/core/java/com/android/server/display/feature/DisplayManagerFlags.java b/services/core/java/com/android/server/display/feature/DisplayManagerFlags.java
index 1a7d74ae1713..8b1a1f524294 100644
--- a/services/core/java/com/android/server/display/feature/DisplayManagerFlags.java
+++ b/services/core/java/com/android/server/display/feature/DisplayManagerFlags.java
@@ -251,6 +251,11 @@ public class DisplayManagerFlags {
             Flags::displayListenerPerformanceImprovements
     );
 
+    private final FlagState mSubscribeGranularDisplayEvents = new FlagState(
+            Flags.FLAG_SUBSCRIBE_GRANULAR_DISPLAY_EVENTS,
+            Flags::subscribeGranularDisplayEvents
+    );
+
     /**
      * @return {@code true} if 'port' is allowed in display layout configuration file.
      */
@@ -537,6 +542,13 @@ public class DisplayManagerFlags {
         return mDisplayListenerPerformanceImprovementsFlagState.isEnabled();
     }
 
+    /**
+     * @return {@code true} if the flag for subscribing to granular display events is enabled
+     */
+    public boolean isSubscribeGranularDisplayEventsEnabled() {
+        return mSubscribeGranularDisplayEvents.isEnabled();
+    }
+
     /**
      * dumps all flagstates
      * @param pw printWriter
@@ -590,6 +602,7 @@ public class DisplayManagerFlags {
         pw.println(" " + mAutoBrightnessModeBedtimeWearFlagState);
         pw.println(" " + mEnablePluginManagerFlagState);
         pw.println(" " + mDisplayListenerPerformanceImprovementsFlagState);
+        pw.println(" " + mSubscribeGranularDisplayEvents);
     }
 
     private static class FlagState {
diff --git a/services/core/java/com/android/server/display/feature/display_flags.aconfig b/services/core/java/com/android/server/display/feature/display_flags.aconfig
index e7ea868ca04f..3976d01d806d 100644
--- a/services/core/java/com/android/server/display/feature/display_flags.aconfig
+++ b/services/core/java/com/android/server/display/feature/display_flags.aconfig
@@ -478,3 +478,14 @@ flag {
     bug: "378385869"
     is_fixed_read_only: true
 }
+
+flag {
+    name: "subscribe_granular_display_events"
+    namespace: "display_manager"
+    description: "Enable subscription to granular display change events."
+    bug: "379250634"
+    is_fixed_read_only: true
+    metadata {
+      purpose: PURPOSE_BUGFIX
+    }
+}
-- 
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