Clip child content to non-uniform border radii - #58490
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Summary: Fixes react#53877. The Issue Uniform Constraint: Previously, the clipping logic relied on UIKit's layer.cornerRadius property whenever the padding-box feature flag was off. This property only supports applying a single, uniform radius to all four corners of a view. Incorrect Rendering: If a layout called for mixed radii (e.g., borderRadius: 36 36 36 0), UIKit would force all four corners to round to 36, causing intended square corners to render as rounded. Content Spillage: Because layer.cornerRadius cannot inset a clip by an uneven border, child backgrounds would spill out of the padding box and paint directly over the parent's borders. This behavior is documented in Issue react#53877. == The change Geometry-Based Masking: The renderer now dynamically selects the clipping mechanism based on the layout geometry. If the border radii are non-uniform, the view uses a layer.mask with a custom shape layer built from the exact per-corner radii and per-side border widths. Optimized Uniform Routing: If the view utilizes standard uniform radii, it continues to take the cheaper, existing cornerRadius path. Direct Image Masking: Since a UIImageView on iOS does not naturally inherit its parent's corner rounding, the new shape mask is applied directly to the image layer so it respects the same non-uniform clipping path. Recycling Hygiene: Because direct image masks persist, new teardown logic was introduced. When a masked view is returned to the recycle pool, the custom clipping masks are cleared. This prevents recycled views from carrying leftover clipping artifacts into their next mount lifecycle. Differential Revision: D119531761
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Summary:
Fixes #53877.
The Issue
Uniform Constraint: Previously, the clipping logic relied on UIKit's layer.cornerRadius property whenever the padding-box feature flag was off. This property only supports applying a single, uniform radius to all four corners of a view.
Incorrect Rendering: If a layout called for mixed radii (e.g., borderRadius: 36 36 36 0), UIKit would force all four corners to round to 36, causing intended square corners to render as rounded.
Content Spillage: Because layer.cornerRadius cannot inset a clip by an uneven border, child backgrounds would spill out of the padding box and paint directly over the parent's borders. This behavior is documented in Issue #53877.
== The change
Geometry-Based Masking: The renderer now dynamically selects the clipping mechanism based on the layout geometry. If the border radii are non-uniform, the view uses a layer.mask with a custom shape layer built from the exact per-corner radii and per-side border widths.
Optimized Uniform Routing: If the view utilizes standard uniform radii, it continues to take the cheaper, existing cornerRadius path.
Direct Image Masking: Since a UIImageView on iOS does not naturally inherit its parent's corner rounding, the new shape mask is applied directly to the image layer so it respects the same non-uniform clipping path.
Recycling Hygiene: Because direct image masks persist, new teardown logic was introduced. When a masked view is returned to the recycle pool, the custom clipping masks are cleared. This prevents recycled views from carrying leftover clipping artifacts into their next mount lifecycle.
Differential Revision: D119531761