SF: Store and manage snapshots for virtual displays

Create/destroy VirtualDisplaySnapshot that tracks the virtual display's
lifetime.

For now, VirtualDisplaySnapshots will track a virtual display's
DisplayId and whether or not it's backed by Hal/Gpu. This will be
helpful when moving the cast system of DisplayIds from within
DisplayId.h to SurfaceFlinger.

Bug: 374163881
Flag: EXEMPT refactor
Test: libsurfaceflinger_unittest
Change-Id: Id730e65b24ecd10925282bd72585ac7c5635a4fe

3 files changed, 92 insertions, 4 deletions

diff --git a/services/surfaceflinger/Display/VirtualDisplaySnapshot.h b/services/surfaceflinger/Display/VirtualDisplaySnapshot.h
new file mode 100644
index 0000000000..c68020ce51
--- /dev/null
+++ b/services/surfaceflinger/Display/VirtualDisplaySnapshot.h
@@ -0,0 +1,52 @@
+/*
+ * Copyright 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <optional>
+#include <string>
+
+#include <ui/DisplayId.h>
+
+#include "Utils/Dumper.h"
+
+namespace android::display {
+
+// Immutable state of a virtual display, captured on creation.
+class VirtualDisplaySnapshot {
+public:
+    VirtualDisplaySnapshot(GpuVirtualDisplayId gpuId, std::string uniqueId)
+          : mIsGpu(true), mUniqueId(std::move(uniqueId)), mVirtualId(gpuId) {}
+    VirtualDisplaySnapshot(HalVirtualDisplayId halId, std::string uniqueId)
+          : mIsGpu(false), mUniqueId(std::move(uniqueId)), mVirtualId(halId) {}
+
+    VirtualDisplayId displayId() const { return mVirtualId; }
+    bool isGpu() const { return mIsGpu; }
+
+    void dump(utils::Dumper& dumper) const {
+        using namespace std::string_view_literals;
+
+        dumper.dump("isGpu"sv, mIsGpu ? "true"sv : "false"sv);
+        dumper.dump("uniqueId"sv, mUniqueId);
+    }
+
+private:
+    const bool mIsGpu;
+    const std::string mUniqueId;
+    const VirtualDisplayId mVirtualId;
+};
+
+} // namespace android::display
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 37b35f2f63..824768203b 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -647,11 +647,12 @@ void SurfaceFlinger::enableHalVirtualDisplays(bool enable) {
     }
 }
 
-VirtualDisplayId SurfaceFlinger::acquireVirtualDisplay(ui::Size resolution,
-                                                       ui::PixelFormat format) {
+VirtualDisplayId SurfaceFlinger::acquireVirtualDisplay(ui::Size resolution, ui::PixelFormat format,
+                                                       const std::string& uniqueId) {
     if (auto& generator = mVirtualDisplayIdGenerators.hal) {
         if (const auto id = generator->generateId()) {
             if (getHwComposer().allocateVirtualDisplay(*id, resolution, &format)) {
+                acquireVirtualDisplaySnapshot(*id, uniqueId);
                 return *id;
             }
 
@@ -665,6 +666,7 @@ VirtualDisplayId SurfaceFlinger::acquireVirtualDisplay(ui::Size resolution,
 
     const auto id = mVirtualDisplayIdGenerators.gpu.generateId();
     LOG_ALWAYS_FATAL_IF(!id, "Failed to generate ID for GPU virtual display");
+    acquireVirtualDisplaySnapshot(*id, uniqueId);
     return *id;
 }
 
@@ -672,6 +674,7 @@ void SurfaceFlinger::releaseVirtualDisplay(VirtualDisplayId displayId) {
     if (const auto id = HalVirtualDisplayId::tryCast(displayId)) {
         if (auto& generator = mVirtualDisplayIdGenerators.hal) {
             generator->releaseId(*id);
+            releaseVirtualDisplaySnapshot(*id);
         }
         return;
     }
@@ -679,6 +682,14 @@ void SurfaceFlinger::releaseVirtualDisplay(VirtualDisplayId displayId) {
     const auto id = GpuVirtualDisplayId::tryCast(displayId);
     LOG_ALWAYS_FATAL_IF(!id);
     mVirtualDisplayIdGenerators.gpu.releaseId(*id);
+    releaseVirtualDisplaySnapshot(*id);
+}
+
+void SurfaceFlinger::releaseVirtualDisplaySnapshot(VirtualDisplayId displayId) {
+    std::lock_guard lock(mVirtualDisplaysMutex);
+    if (!mVirtualDisplays.erase(displayId)) {
+        ALOGW("%s: Virtual display snapshot was not removed", __func__);
+    }
 }
 
 std::vector<PhysicalDisplayId> SurfaceFlinger::getPhysicalDisplayIdsLocked() const {
@@ -3730,7 +3741,7 @@ void SurfaceFlinger::processDisplayAdded(const wp<IBinder>& displayToken,
     if (const auto& physical = state.physical) {
         builder.setId(physical->id);
     } else {
-        builder.setId(acquireVirtualDisplay(resolution, pixelFormat));
+        builder.setId(acquireVirtualDisplay(resolution, pixelFormat, state.uniqueId));
     }
 
     builder.setPixels(resolution);
@@ -5717,6 +5728,14 @@ void SurfaceFlinger::dumpDisplays(std::string& result) const {
             utils::Dumper::Section section(dumper,
                                            ftl::Concat("Virtual Display ", displayId.value).str());
             display->dump(dumper);
+
+            if (const auto virtualIdOpt = VirtualDisplayId::tryCast(displayId)) {
+                std::lock_guard lock(mVirtualDisplaysMutex);
+                const auto virtualSnapshotIt = mVirtualDisplays.find(virtualIdOpt.value());
+                if (virtualSnapshotIt != mVirtualDisplays.end()) {
+                    virtualSnapshotIt->second.dump(dumper);
+                }
+            }
         }
     }
 }
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 7e9d5b881f..cbd47bc22e 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -69,6 +69,7 @@
 #include <common/FlagManager.h>
 #include "Display/DisplayModeController.h"
 #include "Display/PhysicalDisplay.h"
+#include "Display/VirtualDisplaySnapshot.h"
 #include "DisplayDevice.h"
 #include "DisplayHardware/HWC2.h"
 #include "DisplayIdGenerator.h"
@@ -1067,8 +1068,20 @@ private:
     void enableHalVirtualDisplays(bool);
 
     // Virtual display lifecycle for ID generation and HAL allocation.
-    VirtualDisplayId acquireVirtualDisplay(ui::Size, ui::PixelFormat) REQUIRES(mStateLock);
+    VirtualDisplayId acquireVirtualDisplay(ui::Size, ui::PixelFormat, const std::string& uniqueId)
+            REQUIRES(mStateLock);
+    template <typename ID>
+    void acquireVirtualDisplaySnapshot(ID displayId, const std::string& uniqueId) {
+        std::lock_guard lock(mVirtualDisplaysMutex);
+        const bool emplace_success =
+                mVirtualDisplays.try_emplace(displayId, displayId, uniqueId).second;
+        if (!emplace_success) {
+            ALOGW("%s: Virtual display snapshot with the same ID already exists", __func__);
+        }
+    }
+
     void releaseVirtualDisplay(VirtualDisplayId);
+    void releaseVirtualDisplaySnapshot(VirtualDisplayId displayId);
 
     // Returns a display other than `mActiveDisplayId` that can be activated, if any.
     sp<DisplayDevice> getActivatableDisplay() const REQUIRES(mStateLock, kMainThreadContext);
@@ -1269,6 +1282,10 @@ private:
 
     display::PhysicalDisplays mPhysicalDisplays GUARDED_BY(mStateLock);
 
+    mutable std::mutex mVirtualDisplaysMutex;
+    ftl::SmallMap<VirtualDisplayId, const display::VirtualDisplaySnapshot, 2> mVirtualDisplays
+            GUARDED_BY(mVirtualDisplaysMutex);
+
     // The inner or outer display for foldables, while unfolded or folded, respectively.
     std::atomic<PhysicalDisplayId> mActiveDisplayId;