[css-borders-4] Support for curve-based profiles to define custom corner shapes

[777555777]

Currently, the corner-shape property uses a superellipse to define the corners shape. While this is both powerful and intuitive, it is limited in the range of shapes that it can produce.

To increase its flexibility, corner-shape could be given the ability to accept a user defined curve as an alternative option to the superellipse.

This idea is already implemented in Blender’s bevel modifier, where custom profiles can be defined through editable curves.

Such an addition would make it possible to create more complex/stylistic shapes such as pixelated or ornament shaped corners without resorting to workarounds like border-image or clip-path that both come with their limitations or disadvantages.

Example of the feature in Blender

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Pixelated porfile example

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Ornamental profile example

[Crissov]

If you rotated and normalized these for the top-left corner , i.e. to run from lower-left (0,0) to upper-right (1,1), then existing easing functions look a lot like it. 🤔