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Unity Engine

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Script Reference

Unity Engine

Coordinate and position systems

Understand relative and absolute coordinates and transformation between coordinate systems.
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UI Toolkit uses a powerful layout system that automatically calculates the position and size of individual elements based on the layout parameters in their style properties. This is based on Flexbox, a web layout model. For more information, refer to Layout Engine.

Relative and absolute positions

In UI Toolkit, coordinates refer to the position of an element within a layout. You can configure each element in the layout system to use either relative or absolute coordinates:
  • Relative: Coordinates relative to the element’s calculated position. The layout system calculates the position of the element, then adds the coordinates as an offset. Parent elements can influence the size and position of the child elements, as the layout engine takes them into account when it calculates the element position. Child elements can only influence the size of the parent element.
  • Absolute: Coordinates relative to the parent element. This circumvents the automatic layout calculation and directly sets the position of the element. Sibling elements under the same parent have no influence on the element’s position. Similarly, the element doesn't influence the position and size of other siblings under the same parent.
Each visual element determines the coordinate system used to calculate its position. You can configure which coordinate system to use in the element stylesheet.
The following C# code snippets set the coordinate space and the position of a visual element:
var newElement = new VisualElement();newElement.style.position = Position.Relative;newElement.style.left = 15;newElement.style.top = 35;
The origin of an element is its top left corner.
The layout system computes the 
VisualElement.layout
 property (type 
Rect
) for each element, which includes the final position of the element. This takes the relative or absolute position of the element into account.
The 
layout.position
is expressed in points, relative to the coordinate space of its parent.
Each 
VisualElement
has a transform property (
ITransform
) you can use to add an additional local offset to the position and rotation of an element. The offset isn't represented in the calculated layout property. By default, the 
transform
is the identity.
Use the 
worldBound
 property to retrieve the final window space coordinates of the 
VisualElement
, taking into account both the layout position and the transform. This position includes the height of the header of the window.

Transformation between coordinate systems

The 
VisualElement.layout.position
and 
VisualElement.transform
properties define how to transform between the local coordinate system and the parent coordinate system.
The 
VisualElementExtensions
 static class provides the following extension methods that transform points and rectangles between coordinate systems:
  • WorldToLocal
     transforms a 
    Vector2
    or 
    Rect
    from 
    Panel
    space to the referential within the element.
  • LocalToWorld
     transforms a 
    Vector2
    or 
    Rect
    to 
    Panel
    space referential.
  • ChangeCoordinatesTo
     transforms 
    Vector2
    or 
    Rect
    from the local space of one element to the local space of another.

Additional resource