---
title: FxOnScreenControlAPI_v3
framework: Professional Video Applications
role: symbol
role_heading: Protocol
platforms: [fxplug 3.1+]
path: professional_video_applications/fxonscreencontrolapi_v3
---

# FxOnScreenControlAPI_v3

The FxOnScreenControlAPI_v3 protocol specifies additions to the FxOnScreenControlAPI protocol which defines the methods the host application provides to manage conversions between various on-screen coordinate spaces.

## Declaration

```swift
protocol FxOnScreenControlAPI_v3 : FxOnScreenControlAPI_v2
```

## Overview

Overview This protocol inherits from, and expands on, the FxOnScreenControlAPI_v2 protocol. It can retrieve information about the scaling factor used to draw on screen controls to the screen.

## Topics

### Getting Scaling Factor

- [backingScaleFactor()](professional_video_applications/fxonscreencontrolapi_v3/backingscalefactor().md)

## Relationships

### Inherits From

- [FxOnScreenControlAPI](professional_video_applications/fxonscreencontrolapi.md)
- [FxOnScreenControlAPI_v2](professional_video_applications/fxonscreencontrolapi_v2.md)

### Inherited By

- [FxOnScreenControlAPI_v4](professional_video_applications/fxonscreencontrolapi_v4.md)

## See Also

### Onscreen Control APIs

- [FxOnScreenControl_v4](professional_video_applications/fxonscreencontrol_v4.md)
- [FxOnScreenControlAPI](professional_video_applications/fxonscreencontrolapi.md)
- [FxOnScreenControlAPI_v2](professional_video_applications/fxonscreencontrolapi_v2.md)
- [FxOnScreenControlAPI_v4](professional_video_applications/fxonscreencontrolapi_v4.md)