Const
CENTER - CENTER enables the texture to be rendered centered in relation to the element. If the element is smaller than the texture then the background should use the element as stencil to cut off the out-of-bounds area
NINE_SLICES - https://docs.unity3d.com/Manual/UIE-USS-SupportedProperties.html (Slicing section) https://forum.unity.com/threads/how-does-slicing-in-ui-tookkit-works.1235863/ https://docs.unity3d.com/Manual/9SliceSprites.html https://developer.mozilla.org/en-US/docs/Web/CSS/border-image-slice
STRETCH - STRETCH enables the texture to cover all the area of the container, adopting its aspect ratio.
CENTER - CENTER enables the texture to be rendered centered in relation to the element. If the element is smaller than the texture then the background should use the element as stencil to cut off the out-of-bounds area