service/vi: Unstub IApplicationDisplayService' SetLayerScalingMode()

This appears to only check if the scaling mode can actually be
handled, rather than actually setting the scaling mode for the layer.

This implements the same error handling performed on the passed in
values.

src/core/hle/service/vi/vi.cpp

@@ -32,6 +32,9 @@
 
 namespace Service::VI {
 
+constexpr ResultCode ERR_OPERATION_FAILED{ErrorModule::VI, 1};
+constexpr ResultCode ERR_UNSUPPORTED{ErrorModule::VI, 6};
+
 struct DisplayInfo {
     /// The name of this particular display.
     char display_name[0x40]{"Default"};
@@ -874,6 +877,24 @@ public:
     ~IApplicationDisplayService() = default;
 
 private:
+    enum class ConvertedScaleMode : u64 {
+        None = 0, // VI seems to name this as "Unknown" but lots of games pass it, assume it's no
+                  // scaling/default
+        Freeze = 1,
+        ScaleToWindow = 2,
+        Crop = 3,
+        NoCrop = 4,
+    };
+
+    // This struct is different, currently it's 1:1 but this might change in the future.
+    enum class NintendoScaleMode : u32 {
+        None = 0,
+        Freeze = 1,
+        ScaleToWindow = 2,
+        Crop = 3,
+        NoCrop = 4,
+    };
+
     void GetRelayService(Kernel::HLERequestContext& ctx) {
         LOG_WARNING(Service_VI, "(STUBBED) called");
 
@@ -978,13 +999,27 @@ private:
 
     void SetLayerScalingMode(Kernel::HLERequestContext& ctx) {
         IPC::RequestParser rp{ctx};
-        const u32 scaling_mode = rp.Pop<u32>();
+        const auto scaling_mode = rp.PopEnum<NintendoScaleMode>();
         const u64 unknown = rp.Pop<u64>();
 
-        LOG_WARNING(Service_VI, "(STUBBED) called. scaling_mode=0x{:08X}, unknown=0x{:016X}",
-                    scaling_mode, unknown);
+        LOG_DEBUG(Service_VI, "called. scaling_mode=0x{:08X}, unknown=0x{:016X}",
+                    static_cast<u32>(scaling_mode), unknown);
 
         IPC::ResponseBuilder rb{ctx, 2};
+
+        if (scaling_mode > NintendoScaleMode::NoCrop) {
+            LOG_ERROR(Service_VI, "Invalid scaling mode provided.");
+            rb.Push(ERR_OPERATION_FAILED);
+            return;
+        }
+
+        if (scaling_mode != NintendoScaleMode::ScaleToWindow &&
+            scaling_mode != NintendoScaleMode::NoCrop) {
+            LOG_ERROR(Service_VI, "Unsupported scaling mode supplied.");
+            rb.Push(ERR_UNSUPPORTED);
+            return;
+        }
+
         rb.Push(RESULT_SUCCESS);
     }
 
@@ -1065,24 +1100,6 @@ private:
         rb.PushCopyObjects(vsync_event);
     }
 
-    enum class ConvertedScaleMode : u64 {
-        None = 0, // VI seems to name this as "Unknown" but lots of games pass it, assume it's no
-                  // scaling/default
-        Freeze = 1,
-        ScaleToWindow = 2,
-        Crop = 3,
-        NoCrop = 4,
-    };
-
-    // This struct is different, currently it's 1:1 but this might change in the future.
-    enum class NintendoScaleMode : u32 {
-        None = 0,
-        Freeze = 1,
-        ScaleToWindow = 2,
-        Crop = 3,
-        NoCrop = 4,
-    };
-
     void ConvertScalingMode(Kernel::HLERequestContext& ctx) {
         IPC::RequestParser rp{ctx};
         auto mode = rp.PopEnum<NintendoScaleMode>();