Compose an SVG (Scalable Vector Graphics) NFT by concatenating the SVG with the SVG of another NFT rendered as a string for a specific token ID.
Onchain SVG NFTs allow for NFTs to be entirely onchain by returning artwork as SVG in a data URI of the tokenUri function. Composability allows onchain SVG NFTs to be crafted. e.g. adding glasses & hat NFTs to a profile pic NFT or a fish NFT to a fish tank NFT.
The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119.
renderTokenById must return the SVG body for the specified token id and must either be an empty string or valid SVG element(s).
SVG elements can be string concatenated to compose an SVG.
SVG uses a "painters model" of rendering.
Scalable Vector Graphics (SVG) 1.1 (Second Edition), section: 3.3 Rendering Order
Elements in an SVG document fragment have an implicit drawing order, with the first elements in the SVG document fragment getting "painted" first. Subsequent elements are painted on top of previously painted elements.
The ordering of the SVG concatenation determines the drawing order rather than any concept of a z-index.
This EIP only specifies the rendering of the rendered SVG NFT and does not require any specific ordering when composing. This allows the SVG NFT to use a rendered SVG NFT as a foreground or a background as required.
SVG specifies a link tag. Linking could allow for complex SVGs to be composed but would require creating a URI format and then getting ecosystem adoption. As string concatenation of SVG's is already supported, the simpler approach of concatenation is used.
This EIP doesn't specify any requirements on the size of the rendered SVG. Any scaling based on sizing can be performed by the SVG NFT as required.
The render function is named renderTokenById as this function name was first used by Loogies and allows existing deployed NFTs to be compatible with this EIP.
This EIP has no backwards compatibility concerns
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