[service, nvnflinger] Implement GetBufferHistory

Should help with UE4 games and many other buffer dependant titles.
Thanks to master Camille for the code and Shinmegumi for the placement!

Co-authored-by: CamilleLaVey <camillelavey99@gmail.com>
Co-committed-by: CamilleLaVey <camillelavey99@gmail.com>

src/core/hle/service/nvnflinger/buffer_history.h

@@ -0,0 +1,27 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#pragma once
+#include <deque>
+#include <mutex>
+#include <common/assert.h>
+
+struct BufferHistoryEntry { s32 slot; s64 timestamp; s64 frame_number; };
+
+class BufferHistoryManager { public: void PushEntry(s32 slot, s64 timestamp, s64 frame_number) { std::lock_guardstd::mutex lock(mutex_); if (entries_.size() >= kMaxHistorySize) entries_.pop_front();
+
+entries_.emplace_back(BufferHistoryEntry{slot, timestamp, frame_number});
+}
+
+s32 GetHistory(std::span<BufferHistoryEntry> out_entries) {
+    std::lock_guard<std::mutex> lock(mutex_);
+
+    s32 count = std::min(static_cast<s32>(entries_.size()), static_cast<s32>(out_entries.size()));
+
+    for (s32 i = 0; i < count; ++i)
+        out_entries[i] = entries_[entries_.size() - count + i];
+
+    return count;
+}
+
+private: static constexpr size_t kMaxHistorySize = 16; std::deque<BufferHistoryEntry> entries_; std::mutex mutex_; };

src/core/hle/service/nvnflinger/buffer_queue_producer.cpp

@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2021 yuzu Emulator Project
 // SPDX-FileCopyrightText: Copyright 2014 The Android Open Source Project
 // SPDX-License-Identifier: GPL-3.0-or-later
@@ -16,6 +19,7 @@
 #include "core/hle/service/nvnflinger/parcel.h"
 #include "core/hle/service/nvnflinger/ui/graphic_buffer.h"
 #include "core/hle/service/nvnflinger/window.h"
+#include "core/hle/service/nvnflinger/buffer_history.h"
 
 namespace Service::android {
 
@@ -922,11 +926,11 @@ void BufferQueueProducer::Transact(u32 code, std::span<const u8> parcel_data,
         status = SetBufferCount(buffer_count);
         break;
     }
-    case TransactionId::GetBufferHistory:
+    case TransactionId::GetBufferHistory: {
-        LOG_WARNING(Service_Nvnflinger, "(STUBBED) called, transaction=GetBufferHistory");
+        LOG_DEBUG(Service_Nvnflinger, "GetBufferHistory");
-        break;
+        auto out_span = request.PopRaw<std::span<BufferHistoryEntry>>();
-    default:
+        s32 count = buffer_history_.GetHistory(out_span);
-        ASSERT_MSG(false, "Unimplemented TransactionId {}", code);
+        response.Push(s32(count));
         break;
     }
 

src/core/hle/service/nvnflinger/buffer_queue_producer.h

@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2021 yuzu Emulator Project
 // SPDX-FileCopyrightText: Copyright 2014 The Android Open Source Project
 // SPDX-License-Identifier: GPL-3.0-or-later
@@ -80,6 +83,8 @@ private:
 
     std::shared_ptr<BufferQueueCore> core;
     BufferQueueDefs::SlotsType& slots;
+    BufferHistoryManager buffer_history_;
+    buffer_history_.PushEntry(slot, timestamp, frame_number);
     u32 sticky_transform{};
     std::mutex callback_mutex;
     s32 next_callback_ticket{};