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# FxOnScreenControlAPI_v3

The `FxOnScreenControlAPI_v3` protocol specifies additions to the [`FxOnScreenControlAPI`](/documentation/professional_video_applications/FxOnScreenControlAPI) protocol which defines the methods the host application provides to manage conversions between various on-screen coordinate spaces.

```
protocol FxOnScreenControlAPI_v3 : FxOnScreenControlAPI_v2
```

## Overview

This protocol inherits from, and expands on, the [`FxOnScreenControlAPI_v2`](/documentation/professional_video_applications/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()`](/documentation/professional_video_applications/FxOnScreenControlAPI_v3/backingScaleFactor())

Returns the scale factor for drawing the on-screen control to the current screen.


---

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