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# FxOnScreenControlAPI

The `FxOnScreenControlAPI` protocol defines the methods the host application uses to draw controls and other user interface elements directly on the canvas where the user has applied the plug-in.

```
protocol FxOnScreenControlAPI
```

## Overview

Plug-ins use protocol to direct manipulation of the object and is an intuitive means for users to interact with a plug-in.

Use this API to transform points from the drawing space of the canvas or document to the pixel space of the object the user wants to manipulate, and vice-versa.

## Topics

### Converting Points Between Coordinate Spaces

[`convertPoint(fromSpace:fromX:fromY:toSpace:toX:toY:)`](/documentation/professional_video_applications/FxOnScreenControlAPI/convertPoint(fromSpace:fromX:fromY:toSpace:toX:toY:))

Converts a position from object space to canvas space.


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