fix(ios): prevent missing hairlineWidth border strokes at subpixel Y …

[shashikant-panchal]

Summary:

Fixes #58054

Fixes an issue on iOS (Fabric & Legacy renderer) where StyleSheet.hairlineWidth border strokes disappeared when views landed at certain subpixel Y offsets. Removed ceil() rounding from stretchable border image size calculations in RCTBorderDrawing.m and updated CALayer.contentsCenter calculation in RCTViewComponentView.mm and RCTView.m to compute cap sizes dynamically.

Changelog:

[IOS] [BREAKING] - Prevent StyleSheet.hairlineWidth border strokes from disappearing at subpixel Y offsets (#58054) - althought this is a fix, it alters how the apps renders.

Test Plan:

• Rendered views with borderBottomWidth: StyleSheet.hairlineWidth at various fractional Y offsets (y = 100.1, 100.333, 100.5, 100.7).
• Verified 1:1 image cap slice mapping without transparent padding, ensuring hairline border lines remain visible across @2x (0.5pt) and @3x (0.333pt) displays at all offsets.

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[cipolleschi]

Thanks for the fix. I can try to import this as it makes sense on paper, but it might alter how the app behaves. Next release (0.88) is going to be a non breaking change releases, so we have to wait to land this change after we cut the branch (7th of Sept)

[3x]

👀