Implement `IApplicationDisplayService::ConvertScalingMode`

Utilized by アイリス魔法学園

app/src/main/cpp/skyline/services/visrv/IApplicationDisplayService.cpp

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: MPL-2.0
 // Copyright © 2020 Skyline Team and Contributors (https://github.com/skyline-emu/)
+// Copyright © 2019 Ryujinx Team and Contributors
 
 #include <gpu.h>
 #include <kernel/types/KProcess.h>
@@ -85,4 +86,27 @@ namespace skyline::service::visrv {
         response.copyHandles.push_back(handle);
         return {};
     }
+
+    Result IApplicationDisplayService::ConvertScalingMode(type::KSession &session, ipc::IpcRequest &request, ipc::IpcResponse &response) {
+        u32 inScalingMode{request.Pop<u32>()};
+
+        std::array<ScalingMode, 5> scalingModeLut{
+            ScalingMode::None,
+            ScalingMode::Freeze,
+            ScalingMode::ScaleToLayer,
+            ScalingMode::ScaleAndCrop,
+            ScalingMode::PreserveAspectRatio,
+        };
+
+        if (scalingModeLut.size() <= inScalingMode)
+            return result::InvalidArgument;
+
+        auto scalingMode{scalingModeLut[inScalingMode]};
+        if (scalingMode != ScalingMode::ScaleToLayer && scalingMode != ScalingMode::PreserveAspectRatio)
+            return result::IllegalOperation;
+
+        response.Push(scalingMode);
+
+        return {};
+    }
 }

app/src/main/cpp/skyline/services/visrv/IApplicationDisplayService.h

@@ -15,6 +15,17 @@ namespace skyline::service::visrv {
       private:
         PrivilegeLevel level;
 
+        /**
+         * @brief Specifies the method to scale up the layer content to its bounds
+         */
+        enum class ScalingMode {
+            Freeze = 0,
+            ScaleToLayer = 1,
+            ScaleAndCrop = 2,
+            None = 3,
+            PreserveAspectRatio = 4,
+        };
+
       public:
         IApplicationDisplayService(const DeviceState &state, ServiceManager &manager, PrivilegeLevel level);
 
@@ -72,6 +83,11 @@ namespace skyline::service::visrv {
          */
         Result SetLayerScalingMode(type::KSession &session, ipc::IpcRequest &request, ipc::IpcResponse &response);
 
+        /**
+         * @brief Converts an arbitrary scaling mode to a VI scaling mode
+         */
+        Result ConvertScalingMode(type::KSession &session, ipc::IpcRequest &request, ipc::IpcResponse &response);
+
         /**
          * @brief Returns a handle to a KEvent which is triggered every time a frame is drawn
          * @url https://switchbrew.org/wiki/Display_services#GetDisplayVsyncEvent

app/src/main/cpp/skyline/services/visrv/results.h

@@ -6,5 +6,6 @@
 #include <common.h>
 
 namespace skyline::service::visrv::result {
+    constexpr Result InvalidArgument(114, 1);
     constexpr Result IllegalOperation(114, 6);
 }