---
title: HandleChangeScalarValue
framework: VideoDriverKit
role: symbol
role_heading: Instance Method
platforms: [driverkit 27.0+]
path: videodriverkit/iouservideolevelcontrol/handlechangescalarvalue
---

# HandleChangeScalarValue

The system calls this virtual method when the control’s value changes.

## Declaration

```occ
virtual kern_return_t HandleChangeScalarValue(float in_scalar_value);
```

## Parameters

- `in_scalar_value`: The float scalar level value attempting to be set on the control.

## Return Value

Return Value kIOReturnSuccess on success. Upon success the control’s value should be updated.

## Discussion

Discussion The default implementation calls SetScalarValue() and returns kIOReturnSuccess. Subclass and override this method to handle changes to this control value and return kIOReturnSuccess upon success.

## See Also

### Supporting value changes

- [HandleChangeDecibelValue](videodriverkit/iouservideolevelcontrol/handlechangedecibelvalue.md)