video_core: NVIDIA DLSS through NVIDIA Streamline in place of a game's DLSS

Adds a Graphics setting, "Use NVIDIA DLSS in place of a game's DLSS" (nvidia_dlss, off by
default). When it is on, in Windows builds configured with EGLANTINE_STREAMLINE_SDK, the
evaluation Eglantine already replaces with FSR 3.1 goes to NVIDIA DLSS on GeForce RTX cards, with
the same inputs (colour, depth, motion vectors, jitter). When DLSS can't run, FSR 3.1 runs as
before.

Only Streamline's MIT-licensed headers are compiled in; nothing of NVIDIA's is linked or shipped.
At run time Eglantine looks for sl.interposer.dll in the user folder's "streamline" folder (or
EDEN_STREAMLINE_DIR, or "streamline" next to the executable), checks its Streamline signature and
starts Streamline with manual hooking. Streamline's plugins come from that folder or the NVIDIA
app's downloads. DLSS itself is nvngx_dlss.dll in the same folder, else the newest DLSS 310 or
later that the NVIDIA app has downloaded, checked for NVIDIA's Authenticode signature and copied
as streamline/nvidia-app/nvngx_dlss.dll. Like other tools that call DLSS outside a game, it uses
its own fixed project id with the custom engine type.

- Preset K for all modes (EDEN_NX2_DLSS_PRESET overrides it): the default Performance model (M)
  and L draw thin dark horizontal lines in some frames at 2x resolution scale; K doesn't.
- HDR input with auto exposure; the mode follows the render/output ratio.
- Buffer device address stays enabled when DLSS needs it, for DLSS only.
- The upscaler waits for the device instead of submitting when it is destroyed: by then the
  game's channels are released, and a submit read the state tracker's stale flags (a crash when
  stopping a game).

With the setting off, or in builds without the SDK path (the setting is hidden there), nothing
changes.

Testing: Windows 11, RTX 5080, Fire Emblem: Fortune's Weave docked at 1x (720p -> 1440p) and 2x
(1440p -> 2880p), CLI runs and GUI play, stopping and restarting games with DLSS on. Not tested on
other GPUs or games.

Assisted-by: Claude Opus 5.5 (implementation, debugging)
Signed-off-by: Duck912 <350528965+Duck912@users.noreply.github.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/video_core/vulkan_common/vulkan_device.h b/src/video_core/vulkan_common/vulkan_device.h
index edc091318c..3115f4547c 100644
--- a/src/video_core/vulkan_common/vulkan_device.h
+++ b/src/video_core/vulkan_common/vulkan_device.h
@@ -289,6 +289,11 @@ public:
         return physical;
     }
 
+    /// Returns the instance the device was created from.
+    VkInstance GetInstance() const {
+        return instance;
+    }
+
     VkPipelineCache StaticPipelineCache() const noexcept {
         return *static_pipeline_cache;
     }
@@ -1326,6 +1331,8 @@ private:
     // Telemetry parameters
     std::set<std::string, std::less<>> supported_extensions; ///< Reported Vulkan extensions.
     std::set<std::string, std::less<>> loaded_extensions;    ///< Loaded Vulkan extensions.
+    bool streamline_extensions{}; ///< NVIDIA DLSS's extensions are loaded.
+    bool streamline_attached{};   ///< Streamline has this device.
     std::vector<size_t> valid_heap_memory;                   ///< Heaps used.
     size_t main_heap{};       ///< Largest device-local heap, where images live.
     u64 heap_size_limit{};    ///< EDEN_NX2_VRAM_LIMIT_MIB for device-local heaps, 0 if unset.