# layerShader(_:maxSampleOffset:) Returns a filter that applies `shader` to the contents of the source layer. ``` static func layerShader(_ shader: Shader, maxSampleOffset: CGSize) -> GraphicsContext.Filter ``` ## Parameters `shader` The shader to apply as a layer effect. `maxSampleOffset` If the shader function samples from the layer at locations not equal to the destination position, this value must specify the maximum sampling distance in each axis, for all source pixels. ## Return Value A filter applies the shader as a layer effect. ## Discussion For a shader function to act as a layer effect it must have a function signature matching: ``` [[ stitchable ]] half4 name(float2 position, SwiftUI::Layer layer, args...) ``` where `position` is the user-space coordinates of the destination pixel applied to the shader, and `layer` is a rasterized subregion of the source layer. `args...` should be compatible with the uniform arguments bound to `shader`. The `SwiftUI::Layer` type is defined in the `` header file. It exports a single `sample()` function that returns a linearly-filtered pixel value from a position in the source content, as a premultiplied RGBA pixel value: ``` namespace SwiftUI { struct Layer { half4 sample(float2 position) const; }; }; ``` The function should return the color mapping to the destination pixel, typically by sampling one or more pixels from `layer` at location(s) derived from `position` and them applying some kind of transformation to produce a new color. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)