SurfaceFlinger: fix dispatching DISPLAY_EVENT_CONFIG_CHANGED

When setting a new desired config, we might be in the middle of a
previous config changed. We need to maintain the information about
whether we need to generate a config changed event and dispatch it when
we are done with the config switch.

Test: manual test to change config from SF
Bug: 122905403
Change-Id: I7efad63b666e83f6459a65a40e6cc880119ca7f6
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index df2bbc3..8ac7917 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -968,9 +968,11 @@
     }
 
     // Don't check against the current mode yet. Worst case we set the desired
-    // config twice.
+    // config twice. However event generation config might have changed so we need to update it
+    // accordingly
     std::lock_guard<std::mutex> lock(mActiveConfigLock);
-    mDesiredActiveConfig = ActiveConfigInfo{mode, displayToken, event};
+    const ConfigEvent desiredConfig = mDesiredActiveConfig.event | event;
+    mDesiredActiveConfig = ActiveConfigInfo{mode, displayToken, desiredConfig};
 
     if (!mDesiredActiveConfigChanged) {
         // This is the first time we set the desired
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index abc03ec..4dfc29f 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -527,6 +527,13 @@
 
     enum class ConfigEvent { None, Changed };
 
+    // logical or operator with the semantics of at least one of the events is Changed
+    friend ConfigEvent operator|(const ConfigEvent& first, const ConfigEvent& second) {
+        if (first == ConfigEvent::Changed) return ConfigEvent::Changed;
+        if (second == ConfigEvent::Changed) return ConfigEvent::Changed;
+        return ConfigEvent::None;
+    }
+
     // called on the main thread in response to initializeDisplays()
     void onInitializeDisplays() REQUIRES(mStateLock);
     // Sets the desired active config bit. It obtains the lock, and sets mDesiredActiveConfig.