[Bug] [C#] System.Exception: Failed to get result on native API calls during GC/Async tasks

[manups4e]

Summary

Bug Title

Regression in Enhanced Runtime: System.Exception: Failed to get result when invoking CitizenFX Native APIs (GetResInt, SetScaleformMovieAsNoLongerNeeded, GetMouseEvent)

---

Description

Multiple unhandled exceptions occur during runtime in ScaleformUI when running on the Enhanced runtime environment. The same code works without issues on the Legacy runtime.

The script throws System.Exception: Failed to get result across several modules (InstructionalButtonsScaleform, MinimapOverlays, ScaleformWideScreen).

This issue stems from the stricter thread-affinity rules enforced in the Enhanced runtime, where CitizenFX native APIs are invoked from background threads—specifically during Garbage Collection (GC.RunFinalizers / Dispose) or inside async tasks on the .NET ThreadPool.

---

Environment & Regression Context

• Legacy Runtime: Works as expected (native calls succeed even when triggered during GC or async callbacks).
• Enhanced Runtime: Fails consistently with System.Exception: Failed to get result.

---

Stack Traces / Exception Details

1. Native API call in GC Finalizer (ScaleformWideScreen.Dispose)

Error: System.Exception: Failed to get result
Location: System.GC.RunFinalizers() -> ScaleformUI.Scaleforms.ScaleformWideScreen.Finalize()

System.Exception: Failed to get result
   at CitizenFX.Core.Native.API.SetScaleformMovieAsNoLongerNeeded(Int32& scaleformHandle)
   at ScaleformUI.Scaleforms.ScaleformWideScreen.Dispose()
   at ScaleformUI.Scaleforms.ScaleformWideScreen.Finalize()
   at System.GC.RunFinalizers()

• Issue: Calling CitizenFX native functions like SetScaleformMovieAsNoLongerNeeded inside Finalize() executes on the GC background thread rather than the main FiveM execution thread, which fails under Enhanced.

---

2. Screen Resolution / Native Call Failure in InstructionalButtonsScaleform

Error: System.AggregateException: One or more errors occurred. (Failed to get result)

System.AggregateException: One or more errors occurred. (Failed to get result)
 ---> System.Exception: Failed to get result
   at CitizenFX.Core.Native.Api.GetResInt(Int32 idx)
   at CitizenFX.Core.Native.Api.GetActualScreenResolution(Int32& x, Int32& y)
   at CitizenFX.Core.UI.Screen.get_Resolution()
   at ScaleformUI.Scaleforms.InstructionalButtonsScaleform.Load()
   at System.Threading.Tasks.Task...

• Issue: Screen resolution queries (Screen.Resolution / GetResInt) fail when executed off the main thread inside async tasks.

---

3. Tick Handler Exception in MinimapOverlays / ScaleformUIThread_Tick

Error: citizen-scripting-mono Failed to run tick handler ScaleformUIThread_Tick

System.Exception: Failed to get result
   at CitizenFX.Core.Native.API.GetResInt(Int32 idx)
   at CitizenFX.Core.Native.API.GetMouseEvent(Int32 scaleformHandle, Int32& received, Int32& selectionType, Int32& context, Int32& slotIndex)
   at ScaleformUI.Scaleforms.MinimapOverlays.Update()
   at ScaleformUI.Main.ScaleformUIThread_Tick()

---

Suggested Fixes / Expected Behavior

• Explicit Disposal on Main Thread: Avoid placing CitizenFX native cleanup logic (SetScaleformMovieAsNoLongerNeeded, etc.) inside destructors/finalizers (~Class() or Finalize()). Native resources should be explicitly disposed of on the main tick thread before references are dropped.
• Thread Marshalling: Ensure async methods switch back to the main execution context (e.g., await BaseScript.Delay(0)) before querying game native functions like GetResInt or GetMouseEvent.

Issue type

Client

Repro rate

Always

Server build version

FXServer-early-access b94 win32

OS

No response

CPU

No response

GPU

No response

RAM

No response

Storage type

None

Connection type

None

ISP and bandwidth

No response

DxDiag

No response

Network graph

No response

Platform

None

OS version / distribution

No response

CPU

No response

RAM

No response

Using txAdmin?

None

Hosting provider

None

Machine type

None

/perf endpoint output

No response

DDoS protection

No response

ulimit -n value (Linux only)

No response

Docker Compose file (Docker only)

No response

Steps to Reproduce

1. Download ScaleformUI_CSharp + ScaleformUI_Assets
2. Start it
3. Enjoy the explosions

Expected Behavior

• CitizenFX native APIs should execute successfully when invoked by ScaleformUI on the Enhanced runtime, maintaining parity with the Legacy runtime behavior.
• Resource disposal and resolution queries should properly marshal native calls to the main execution thread to prevent cross-thread native invocation failures.

Actual Behavior

• Native API calls (e.g., GetResInt, SetScaleformMovieAsNoLongerNeeded, GetMouseEvent) throw System.Exception: Failed to get result on the Enhanced runtime.
• The script crashes or throws unhandled exceptions during Garbage Collection (GC.RunFinalizers) and async execution loops (ScaleformUIThread_Tick, InstructionalButtonsScaleform.Load).

Evidence

[23-07-2026 16:18:16] [   error] [                ] Failed to run tick handler ScaleformUIThread_Tick: System.Exception: Failed to get result
   at CitizenFX.Base.NativeApi.GetResInt(Int32 idx)
   at CitizenFX.Core.Native.API.GetMouseEvent(Int32 scaleformHandle, Int32& received, Int32& selectionType, Int32& context, Int32& slotIndex)
   at ScaleformUI.Scaleforms.MinimapOverlays.Update()
   at ScaleformUI.Main.ScaleformUIThread_Tick()
   at CitizenFX.Core.BaseScript.InvokeTickHandler(TickHandler handler)
[23-07-2026 16:18:16] [   error] [                ] Failed to run tick handler ScaleformUIThread_Tick: System.Exception: Failed to get result
   at CitizenFX.Base.NativeApi.GetResInt(Int32 idx)
   at CitizenFX.Core.Native.API.GetMouseEvent(Int32 scaleformHandle, Int32& received, Int32& selectionType, Int32& context, Int32& slotIndex)
   at ScaleformUI.Scaleforms.MinimapOverlays.Update()
   at ScaleformUI.Main.ScaleformUIThread_Tick()
   at CitizenFX.Core.BaseScript.InvokeTickHandler(TickHandler handler)

Additional Context

No response

[europium-cfx]

Hey! There was a major issue involving native invocation for some specific native calls (mostly those with ref arguments), including SetScaleformMovieAsNoLongerNeeded and GetMouseEvent, that was not related with threading issues. Those natives should be already fixed with CitizenFX.FiveM.Client 0.0.2-alpha and will be fixed in the next patch for the backwards compatibility module.

However, we'll look deeper into potentials issues that could arise from calling natives from the background GC thread.

[manups4e]

Thanks!! The wrapper is in mono (legacy mode) for now. I'm planning to port it to the new API in the future!

[manups4e]

i Updated both client and server to latest build (b97 clientside)

Starting ScaleformUI_CSharp (mono legacy)

[manups4e]

Regardiung the Resolution thingy that errors out...
ScaleformUI like some of my not working custom scaleforms relies on BaseScreenLayout.as class which is an actionscript class that calls the internal C++ API to get the game resolution and pass it to the scaleform via callbacks (same way as InstructionalButtons)

using

	function getDisplayConfig(shouldSet)
	{
		if (shouldSet == undefined)
		{
			shouldSet = true;
		}
		var _loc2_ = new com.rockstargames.ui.utils.DisplayConfig();
		com.rockstargames.ui.game.GameInterface.call("SET_DISPLAY_CONFIG",com.rockstargames.ui.game.GameInterface.GENERIC_TYPE,_loc2_);
		if (shouldSet)
		{
			this.SET_DISPLAY_CONFIG(_loc2_.screenWidth,_loc2_.screenHeight,_loc2_.safeTop,_loc2_.safeBottom,_loc2_.safeLeft,_loc2_.safeRight,_loc2_.isWideScreen,_loc2_.isCircleAccept,_loc2_.isAsian);
		}
		return _loc2_;
	}

the SET_DISPLAY_CONFIG function is then passed to the inheriting class (ScaleformUI in my case) and i suspect that other scaleforms like in
#378 are not working due to the internal API being called and probably crashing the loading process of the scaleform itself.