Rename invalid LayerStacks to "unassigned"

"Invalid" can be confusing since this LayerStack value
is actually valid and can be used to represent offscreen
layers.

Bug: b/397775142
Test: atest SurfaceFlinger_test
Flag: EXEMPT, renaming
Change-Id: I1432107ae4a088aecc5baefad7db54e49cdc7bbf

Author: Melody Hsu

libs/ui/include/ui/LayerStack.h

@@ -25,7 +25,7 @@
 namespace android::ui {
 
 // A LayerStack identifies a Z-ordered group of layers. A layer can only be associated to a single
-// LayerStack, but a LayerStack can be associated to multiple displays, mirroring the same content.
+// LayerStack, and a LayerStack should be unique to each display in the composition target.
 struct LayerStack {
     uint32_t id = UINT32_MAX;
 
@@ -40,7 +40,9 @@ struct LayerStack {
     }
 };
 
-constexpr LayerStack INVALID_LAYER_STACK;
+// An unassigned LayerStack can indicate that a layer is offscreen and will not be
+// rendered onto a display. Multiple displays are allowed to have unassigned LayerStacks.
+constexpr LayerStack UNASSIGNED_LAYER_STACK;
 constexpr LayerStack DEFAULT_LAYER_STACK{0u};
 
 inline bool operator==(LayerStack lhs, LayerStack rhs) {
@@ -70,7 +72,7 @@ struct LayerFilter {
     // Returns true if the input filter can be output to this filter.
     bool includes(LayerFilter other) const {
         // The layer stacks must match.
-        if (other.layerStack == INVALID_LAYER_STACK || other.layerStack != layerStack) {
+        if (other.layerStack == UNASSIGNED_LAYER_STACK || other.layerStack != layerStack) {
             return false;
         }
 

services/surfaceflinger/CompositionEngine/tests/DisplayTest.cpp

@@ -302,7 +302,7 @@ TEST_F(DisplaySetConfigurationTest, configuresPhysicalDisplay) {
     EXPECT_FALSE(mDisplay->isValid());
 
     const auto& filter = mDisplay->getState().layerFilter;
-    EXPECT_EQ(ui::INVALID_LAYER_STACK, filter.layerStack);
+    EXPECT_EQ(ui::UNASSIGNED_LAYER_STACK, filter.layerStack);
     EXPECT_FALSE(filter.toInternalDisplay);
 }
 
@@ -322,7 +322,7 @@ TEST_F(DisplaySetConfigurationTest, configuresHalVirtualDisplay) {
     EXPECT_FALSE(mDisplay->isValid());
 
     const auto& filter = mDisplay->getState().layerFilter;
-    EXPECT_EQ(ui::INVALID_LAYER_STACK, filter.layerStack);
+    EXPECT_EQ(ui::UNASSIGNED_LAYER_STACK, filter.layerStack);
     EXPECT_FALSE(filter.toInternalDisplay);
 }
 
@@ -342,7 +342,7 @@ TEST_F(DisplaySetConfigurationTest, configuresGpuVirtualDisplay) {
     EXPECT_FALSE(mDisplay->isValid());
 
     const auto& filter = mDisplay->getState().layerFilter;
-    EXPECT_EQ(ui::INVALID_LAYER_STACK, filter.layerStack);
+    EXPECT_EQ(ui::UNASSIGNED_LAYER_STACK, filter.layerStack);
     EXPECT_FALSE(filter.toInternalDisplay);
 }
 

services/surfaceflinger/CompositionEngine/tests/OutputTest.cpp

@@ -646,8 +646,8 @@ TEST_F(OutputTest, layerFiltering) {
     mOutput->setLayerFilter({layerStack1, true});
 
     // It excludes layers with no layer stack, internal-only or not.
-    EXPECT_FALSE(mOutput->includesLayer({ui::INVALID_LAYER_STACK, false}));
-    EXPECT_FALSE(mOutput->includesLayer({ui::INVALID_LAYER_STACK, true}));
+    EXPECT_FALSE(mOutput->includesLayer({ui::UNASSIGNED_LAYER_STACK, false}));
+    EXPECT_FALSE(mOutput->includesLayer({ui::UNASSIGNED_LAYER_STACK, true}));
 
     // It includes layers on layerStack1, internal-only or not.
     EXPECT_TRUE(mOutput->includesLayer({layerStack1, false}));
@@ -685,10 +685,10 @@ TEST_F(OutputTest, layerFilteringWithCompositionState) {
     mOutput->setLayerFilter({layerStack1, true});
 
     // It excludes layers with no layer stack, internal-only or not.
-    layer.layerFEState.outputFilter = {ui::INVALID_LAYER_STACK, false};
+    layer.layerFEState.outputFilter = {ui::UNASSIGNED_LAYER_STACK, false};
     EXPECT_FALSE(mOutput->includesLayer(layerFE));
 
-    layer.layerFEState.outputFilter = {ui::INVALID_LAYER_STACK, true};
+    layer.layerFEState.outputFilter = {ui::UNASSIGNED_LAYER_STACK, true};
     EXPECT_FALSE(mOutput->includesLayer(layerFE));
 
     // It includes layers on layerStack1, internal-only or not.

services/surfaceflinger/FrontEnd/LayerCreationArgs.cpp

@@ -86,7 +86,7 @@ std::string LayerCreationArgs::getDebugString() const {
     if (layerIdToMirror != UNASSIGNED_LAYER_ID) {
         stream << " layerIdToMirror=" << layerIdToMirror;
     }
-    if (layerStackToMirror != ui::INVALID_LAYER_STACK) {
+    if (layerStackToMirror != ui::UNASSIGNED_LAYER_STACK) {
         stream << " layerStackToMirror=" << layerStackToMirror.id;
     }
     return stream.str();

services/surfaceflinger/FrontEnd/LayerCreationArgs.h

@@ -58,7 +58,7 @@ struct LayerCreationArgs {
     bool addToRoot = true;
     wp<IBinder> parentHandle = nullptr;
     wp<IBinder> mirrorLayerHandle = nullptr;
-    ui::LayerStack layerStackToMirror = ui::INVALID_LAYER_STACK;
+    ui::LayerStack layerStackToMirror = ui::UNASSIGNED_LAYER_STACK;
     uint32_t parentId = UNASSIGNED_LAYER_ID;
     uint32_t layerIdToMirror = UNASSIGNED_LAYER_ID;
     std::atomic<int32_t>* pendingBuffers = 0;

services/surfaceflinger/FrontEnd/LayerLifecycleManager.cpp

@@ -55,10 +55,10 @@ void LayerLifecycleManager::addLayers(std::vector<std::unique_ptr<RequestedLayer
         mChangedLayers.push_back(newLayer.get());
         layer.parentId = linkLayer(layer.parentId, layer.id);
         layer.relativeParentId = linkLayer(layer.relativeParentId, layer.id);
-        if (layer.layerStackToMirror != ui::INVALID_LAYER_STACK) {
+        if (layer.layerStackToMirror != ui::UNASSIGNED_LAYER_STACK) {
             // Set mirror layer's default layer stack to -1 so it doesn't end up rendered on a
             // display accidentally.
-            layer.layerStack = ui::INVALID_LAYER_STACK;
+            layer.layerStack = ui::UNASSIGNED_LAYER_STACK;
 
             // if this layer is mirroring a display, then walk though all the existing root layers
             // for the layer stack and add them as children to be mirrored.
@@ -124,7 +124,7 @@ void LayerLifecycleManager::onHandlesDestroyed(
 
         layer.parentId = unlinkLayer(layer.parentId, layer.id);
         layer.relativeParentId = unlinkLayer(layer.relativeParentId, layer.id);
-        if (layer.layerStackToMirror != ui::INVALID_LAYER_STACK) {
+        if (layer.layerStackToMirror != ui::UNASSIGNED_LAYER_STACK) {
             layer.mirrorIds = unlinkLayers(layer.mirrorIds, layer.id);
             swapErase(mDisplayMirroringLayers, layer.id);
         } else {

services/surfaceflinger/FrontEnd/LayerSnapshotBuilder.cpp

@@ -784,7 +784,7 @@ void LayerSnapshotBuilder::updateSnapshot(LayerSnapshot& snapshot, const Args& a
         // Display mirrors are always placed in a VirtualDisplay so we never want to capture layers
         // marked as skip capture
         snapshot.handleSkipScreenshotFlag = parentSnapshot.handleSkipScreenshotFlag ||
-                (requested.layerStackToMirror != ui::INVALID_LAYER_STACK);
+                (requested.layerStackToMirror != ui::UNASSIGNED_LAYER_STACK);
     }
 
     if (forceUpdate || snapshot.clientChanges & layer_state_t::eAlphaChanged) {

services/surfaceflinger/FrontEnd/RequestedLayerState.cpp

@@ -73,7 +73,7 @@ RequestedLayerState::RequestedLayerState(const LayerCreationArgs& args)
     }
     if (layerIdToMirror != UNASSIGNED_LAYER_ID) {
         changes |= RequestedLayerState::Changes::Mirror;
-    } else if (args.layerStackToMirror != ui::INVALID_LAYER_STACK) {
+    } else if (args.layerStackToMirror != ui::UNASSIGNED_LAYER_STACK) {
         layerStackToMirror = args.layerStackToMirror;
         changes |= RequestedLayerState::Changes::Mirror;
     }

services/surfaceflinger/FrontEnd/RequestedLayerState.h

@@ -128,7 +128,7 @@ struct RequestedLayerState : layer_state_t {
     uint32_t parentId = UNASSIGNED_LAYER_ID;
     uint32_t relativeParentId = UNASSIGNED_LAYER_ID;
     uint32_t layerIdToMirror = UNASSIGNED_LAYER_ID;
-    ui::LayerStack layerStackToMirror = ui::INVALID_LAYER_STACK;
+    ui::LayerStack layerStackToMirror = ui::UNASSIGNED_LAYER_STACK;
     uint32_t touchCropId = UNASSIGNED_LAYER_ID;
     uint32_t bgColorLayerId = UNASSIGNED_LAYER_ID;
     uint64_t barrierFrameNumber = 0;

services/surfaceflinger/SurfaceFlinger.cpp

@@ -2887,7 +2887,8 @@ CompositeResultsPerDisplay SurfaceFlinger::composite(
     ui::DisplayMap<ui::LayerStack, ftl::Unit> outputLayerStacks;
     auto isUniqueOutputLayerStack = [&outputLayerStacks](DisplayId id, ui::LayerStack layerStack) {
         if (FlagManager::getInstance().reject_dupe_layerstacks()) {
-            if (layerStack != ui::INVALID_LAYER_STACK && outputLayerStacks.contains(layerStack)) {
+            if (layerStack != ui::UNASSIGNED_LAYER_STACK &&
+                outputLayerStacks.contains(layerStack)) {
                 // TODO: remove log and DisplayId from params once reject_dupe_layerstacks flag is
                 // removed
                 ALOGD("Existing layer stack ID %d output to another display %" PRIu64
@@ -3016,9 +3017,9 @@ CompositeResultsPerDisplay SurfaceFlinger::composite(
                         LayerFE::ReleaseFencePromiseStatus::UNINITIALIZED ||
                 layerFE->getReleaseFencePromiseStatus() ==
                         LayerFE::ReleaseFencePromiseStatus::FULFILLED) {
-                // layerStack is invalid because layer is not on a display
+                // layerStack is unassigned because layer is not on a display
                 attachReleaseFenceFutureToLayer(layer.get(), layerFE.get(),
-                                                ui::INVALID_LAYER_STACK);
+                                                ui::UNASSIGNED_LAYER_STACK);
             }
         }
     }
@@ -3035,13 +3036,13 @@ CompositeResultsPerDisplay SurfaceFlinger::composite(
 
     int index = 0;
     ftl::StaticVector<char, WorkloadTracer::COMPOSITION_SUMMARY_SIZE> compositionSummary;
-    auto lastLayerStack = ui::INVALID_LAYER_STACK;
+    auto lastLayerStack = ui::UNASSIGNED_LAYER_STACK;
 
     uint64_t prevOverrideBufferId = 0;
     for (auto& [layer, layerFE] : layers) {
         CompositionResult compositionResult{layerFE->stealCompositionResult()};
         if (lastLayerStack != layerFE->mSnapshot->outputFilter.layerStack) {
-            if (lastLayerStack != ui::INVALID_LAYER_STACK) {
+            if (lastLayerStack != ui::UNASSIGNED_LAYER_STACK) {
                 // add a space to separate displays
                 compositionSummary.push_back(' ');
             }
@@ -3356,7 +3357,7 @@ void SurfaceFlinger::onCompositionPresented(PhysicalDisplayId pacesetterId,
             if (optDisplay && !optDisplay->get()->isVirtual()) {
                 auto fence = getHwComposer().getPresentFence(optDisplay->get()->getPhysicalId());
                 layer->prepareReleaseCallbacks(ftl::yield<FenceResult>(fence),
-                                               ui::INVALID_LAYER_STACK);
+                                               ui::UNASSIGNED_LAYER_STACK);
             }
         }
         layer->releasePendingBuffer(presentTime.ns());
@@ -6219,7 +6220,7 @@ void SurfaceFlinger::dumpHdrInfo(std::string& result) const {
 void SurfaceFlinger::dumpFrontEnd(std::string& result) {
     std::ostringstream out;
     out << "\nComposition list (bottom to top)\n";
-    ui::LayerStack lastPrintedLayerStackHeader = ui::INVALID_LAYER_STACK;
+    ui::LayerStack lastPrintedLayerStackHeader = ui::UNASSIGNED_LAYER_STACK;
     for (const auto& snapshot : mLayerSnapshotBuilder.getSnapshots()) {
         if (lastPrintedLayerStackHeader != snapshot->outputFilter.layerStack) {
             lastPrintedLayerStackHeader = snapshot->outputFilter.layerStack;
@@ -6229,7 +6230,7 @@ void SurfaceFlinger::dumpFrontEnd(std::string& result) {
     }
 
     out << "\nInput list\n";
-    lastPrintedLayerStackHeader = ui::INVALID_LAYER_STACK;
+    lastPrintedLayerStackHeader = ui::UNASSIGNED_LAYER_STACK;
     mLayerSnapshotBuilder.forEachInputSnapshot([&](const frontend::LayerSnapshot& snapshot) {
         if (lastPrintedLayerStackHeader != snapshot.outputFilter.layerStack) {
             lastPrintedLayerStackHeader = snapshot.outputFilter.layerStack;
@@ -6247,7 +6248,7 @@ void SurfaceFlinger::dumpFrontEnd(std::string& result) {
 void SurfaceFlinger::dumpVisibleFrontEnd(std::string& result) {
     std::ostringstream out;
     out << "\nComposition list (bottom to top)\n";
-    ui::LayerStack lastPrintedLayerStackHeader = ui::INVALID_LAYER_STACK;
+    ui::LayerStack lastPrintedLayerStackHeader = ui::UNASSIGNED_LAYER_STACK;
     mLayerSnapshotBuilder.forEachVisibleSnapshot(
             [&](std::unique_ptr<frontend::LayerSnapshot>& snapshot) {
                 if (snapshot->hasSomethingToDraw()) {
@@ -6260,7 +6261,7 @@ void SurfaceFlinger::dumpVisibleFrontEnd(std::string& result) {
             });
 
     out << "\nInput list\n";
-    lastPrintedLayerStackHeader = ui::INVALID_LAYER_STACK;
+    lastPrintedLayerStackHeader = ui::UNASSIGNED_LAYER_STACK;
     mLayerSnapshotBuilder.forEachInputSnapshot([&](const frontend::LayerSnapshot& snapshot) {
         if (lastPrintedLayerStackHeader != snapshot.outputFilter.layerStack) {
             lastPrintedLayerStackHeader = snapshot.outputFilter.layerStack;
@@ -7693,7 +7694,7 @@ bool SurfaceFlinger::getSnapshotsFromMainThread(
                 if (mRenderEngine->isThreaded()) {
                     for (auto& [layer, layerFE] : layers) {
                         attachReleaseFenceFutureToLayer(layer, layerFE.get(),
-                                                        ui::INVALID_LAYER_STACK);
+                                                        ui::UNASSIGNED_LAYER_STACK);
                     }
                 }
                 return getDisplayStateOnMainThread(args);
@@ -7975,7 +7976,7 @@ ftl::SharedFuture<FenceResult> SurfaceFlinger::renderScreenImpl(
             // deadlocks between main thread and binder threads waiting for the future fence
             // result, fences should be added to layers in the same hop onto the main thread.
             if (!mRenderEngine->isThreaded()) {
-                attachReleaseFenceFutureToLayer(layer, layerFE.get(), ui::INVALID_LAYER_STACK);
+                attachReleaseFenceFutureToLayer(layer, layerFE.get(), ui::UNASSIGNED_LAYER_STACK);
             }
             layerFEs.push_back(layerFE);
         }