[sf] provide a unique id for snapshots

Input and layer tracing relies on the fact that all layers
have a unique id. Because mirror layers are no longer
implemented by duplicating layers, we can have multiple
snapshots with the same id. To fix this, provide a unique
id that can be used by consumers who require them.

Test: atest FlickerTest
Bug: 238781169
Change-Id: Ibe54154b6e14f72bfe73a15faa0e7e0d19293e36

4 files changed, 14 insertions, 3 deletions

diff --git a/services/surfaceflinger/FrontEnd/LayerSnapshot.cpp b/services/surfaceflinger/FrontEnd/LayerSnapshot.cpp
index 85b00d77b4..8a450933f0 100644
--- a/services/surfaceflinger/FrontEnd/LayerSnapshot.cpp
+++ b/services/surfaceflinger/FrontEnd/LayerSnapshot.cpp
@@ -27,12 +27,16 @@ using namespace ftl::flag_operators;
 LayerSnapshot::LayerSnapshot(const RequestedLayerState& state,
                              const LayerHierarchy::TraversalPath& path)
       : path(path) {
+    static uint32_t sUniqueSequenceId = 0;
+    // Provide a unique id for clones otherwise keeping using the sequence id.
+    // The seq id can still be useful for debugging if its available.
+    uniqueSequence = (path.isClone()) ? sUniqueSequenceId++ : state.id;
     sequence = static_cast<int32_t>(state.id);
     name = state.name;
     textureName = state.textureName;
     premultipliedAlpha = state.premultipliedAlpha;
     inputInfo.name = state.name;
-    inputInfo.id = static_cast<int32_t>(state.id);
+    inputInfo.id = static_cast<int32_t>(uniqueSequence);
     inputInfo.ownerUid = static_cast<int32_t>(state.ownerUid);
     inputInfo.ownerPid = state.ownerPid;
     changes = RequestedLayerState::Changes::Created;
diff --git a/services/surfaceflinger/FrontEnd/LayerSnapshot.h b/services/surfaceflinger/FrontEnd/LayerSnapshot.h
index 07aa12269a..e069a63201 100644
--- a/services/surfaceflinger/FrontEnd/LayerSnapshot.h
+++ b/services/surfaceflinger/FrontEnd/LayerSnapshot.h
@@ -57,6 +57,12 @@ struct LayerSnapshot : public compositionengine::LayerFECompositionState {
     bool isHiddenByPolicyFromParent = false;
     bool isHiddenByPolicyFromRelativeParent = false;
     ftl::Flags<RequestedLayerState::Changes> changes;
+    // Some consumers of this snapshot (input, layer traces) rely on each snapshot to be unique.
+    // For mirrored layers, snapshots will have the same sequence so this unique id provides
+    // an alternative identifier when needed.
+    uint32_t uniqueSequence;
+    // Layer id used to create this snapshot. Multiple snapshots will have the same sequence if they
+    // generated from the same layer, for example when mirroring.
     int32_t sequence;
     std::string name;
     uint32_t textureName;
diff --git a/services/surfaceflinger/FrontEnd/LayerSnapshotBuilder.cpp b/services/surfaceflinger/FrontEnd/LayerSnapshotBuilder.cpp
index db6e716311..344dab4522 100644
--- a/services/surfaceflinger/FrontEnd/LayerSnapshotBuilder.cpp
+++ b/services/surfaceflinger/FrontEnd/LayerSnapshotBuilder.cpp
@@ -957,7 +957,7 @@ void LayerSnapshotBuilder::updateInput(LayerSnapshot& snapshot,
     }
 
     snapshot.inputInfo.name = requested.name;
-    snapshot.inputInfo.id = static_cast<int32_t>(requested.id);
+    snapshot.inputInfo.id = static_cast<int32_t>(snapshot.uniqueSequence);
     snapshot.inputInfo.ownerUid = static_cast<int32_t>(requested.ownerUid);
     snapshot.inputInfo.ownerPid = requested.ownerPid;
     snapshot.inputInfo.displayId = static_cast<int32_t>(snapshot.outputFilter.layerStack.id);
diff --git a/services/surfaceflinger/LayerProtoHelper.cpp b/services/surfaceflinger/LayerProtoHelper.cpp
index 1a828bf88c..55281fa962 100644
--- a/services/surfaceflinger/LayerProtoHelper.cpp
+++ b/services/surfaceflinger/LayerProtoHelper.cpp
@@ -260,6 +260,7 @@ void LayerProtoHelper::writeHierarchyToProto(
     frontend::LayerSnapshot* snapshot = snapshotBuilder.getSnapshot(layer.id);
 
     if (!snapshot) {
+        defaultSnapshot.uniqueSequence = layer.id;
         snapshot = &defaultSnapshot;
     }
     writeSnapshotToProto(layerProto, layer, *snapshot, traceFlags);
@@ -343,7 +344,7 @@ void LayerProtoHelper::writeSnapshotToProto(LayerProto* layerInfo,
                                    [&]() { return layerInfo->mutable_corner_radius_crop(); });
     layerInfo->set_shadow_radius(snapshot.shadowRadius);
 
-    layerInfo->set_id(requestedState.id);
+    layerInfo->set_id(snapshot.uniqueSequence);
     layerInfo->set_name(requestedState.name);
     layerInfo->set_type("Layer");