Checking a system-defined enum with equality operators fails | Voters

Checking a system-defined enum with equality operators fails

naqtn

Checking the equality/inequality of a system-defined enum with equality/inequality operators (

) will fail.

As a result, this example codes in the document don't work as expected: https://creators.vrchat.com/platforms/android/android-best-practices/#2-detect-mobile-players-in-your-world-automatically

public override void OnInputMethodChanged(VRCInputMethod inputMethod)  
{  
    if (inputMethod == VRCInputMethod.Touch)  
    {  
        // Run code for touch input  
    }  
    else  
    {  
        // Run code for non-touch input  
    }  
}

(The UdonGraph version (attached image) also has an identical issue.)

Workaround

Cast to underlying values and compare them.

if ((int)inputMethod == (int)VRCInputMethod.Touch)

Analysis

UdonSharp compiles the expression

inputMethod == VRCInputMethod.Touch

into

EXTERN, "SystemObject.__Equals__SystemObject__SystemBoolean"

Although

Object.Equals(Object)

is overridden by

Enum.Equals(Object)

, which the

inputMethod

may have, with comparing underlying value, this

EXTERN

seems to call the

Object.Equals

directly (maybe via reflection API), and it returns the unexpected result (by only comparing the referencing instances).

The

EXTERN, "SystemObject.__Equals__

comes from here https://github.com/vrchat-community/UdonSharp/blob/22307065bd408dfd163fe46b0b8b701a4efcbc00/Packages/com.vrchat.UdonSharp/Editor/Compiler/Binder/BoundNodes/BoundInvocationExpression.cs#L420 And replacing the

System_Object

of this line with

System_Enum

doesn't work because the

Enum.Equals

is not exposed.

Suggestions

Temporary, rewrite the example codes using cast operator
Expose
System.Enum.Equals
And replace the
EXTERN
with
System.Enum.Equals

October 1, 2024

Μerlin

public class EnumTest : UdonSharpBehaviour
{
    public VRCInputMethod inputMethod;
    void Start()
    {
        Debug.Log($"Input method: {inputMethod}");
        Debug.Log($"Input method == Touch: {inputMethod == VRCInputMethod.Touch}");
        Debug.Log($"Input method != Touch: {inputMethod != VRCInputMethod.Touch}");
        Debug.Log($"Input method == Gaze: {inputMethod == VRCInputMethod.Gaze}");
        Debug.Log($"Input method != Gaze: {inputMethod != VRCInputMethod.Gaze}");
    }
}

This appears to work as expected in-editor and in-game on desktop with the

inputMethod

set to Touch. Note: calling .Equals() on an

object

should call the virtual inherited member of that type so it would be calling the inherited enum.Equals() even though it isn't directly exposed. Maybe this is a mobile-specific issue, or the input method changed event isn't getting the expected argument always?

naqtn

Μerlin Thank you for the info and testing. I realized that my analysis was wrong and found another possibility of the cause.

The type of the

OnInputMethodChanged

argument and the type of the constant in the heap differ, although both are

VRCInputMethod

on the source code. If so,

Enum.Equals

may return false.

    public override void OnInputMethodChanged(VRCInputMethod inputMethod)
    {
        Debug.Log($"OnInputMethodChanged inputMethod={inputMethod}");
	// Comparing to VRCInputMethod.Keyboard to be easy to test on PC 
        Debug.Log($"inputMethod == VRCInputMethod.Keyboard: {inputMethod == VRCInputMethod.Keyboard}");
        Debug.Log($"(int)inputMethod == (int)VRCInputMethod.Keyboard: {(int)inputMethod == (int)VRCInputMethod.Keyboard}");
	// Examin the types
	System.Type argType = inputMethod.GetType();
	System.Type constType = VRCInputMethod.Keyboard.GetType();
        Debug.Log($"argType == constType: {argType == constType}");
        Debug.Log($"argType.FullName={argType.FullName}");
        Debug.Log($"constType.FullName={constType.FullName}");
    }

 Log        -  OnInputMethodChanged inputMethod=Keyboard
 Log        -  inputMethod == VRCInputMethod.Keyboard: False
 Log        -  (int)inputMethod == (int)VRCInputMethod.Keyboard: True
 Log        -  argType == constType: False
 Log        -  argType.FullName=ÏÎÎÌÎÌÍÌÎÎÌÌÏÏÎÌÌÎÎÍÌÌÌ+ÎÍÍÏÌÌÍÏÏÎÍÎÍÍÍÎÌÌÎÎÎÍÌ
 Log        -  constType.FullName=VRC.SDKBase.VRCInputMethod

I forgot to note the versions. SDK 3.7.1, Client 2024.3.2p2 build 1506