borderWidth renders at double thickness when borderRadius is an array (iOS)

[macCesar]

Summary

A View with borderWidth: N and borderRadius: [top, right, bottom, left] on iOS draws the border at 2N points instead of N. The doubling is consistent and reproduces with or without viewShadowColor. Replacing the array with a scalar borderRadius: N renders the border at the correct N.

Reproduction

const win = Ti.UI.createWindow({ backgroundColor: 'gray' });

win.add(Ti.UI.createView({
  width: 300,
  height: 200,
  backgroundColor: 'white',
  borderColor: 'magenta',
  borderWidth: 4,
  borderRadius: [24, 24, 0, 0]  // top corners rounded, bottom square
}));

win.open();

Expected: a 4dp magenta border.
Actual: an 8dp magenta border, growing inward.

Swap borderRadius: [24, 24, 0, 0] for borderRadius: 24 and the border renders at 4dp as declared.

Root cause

iphone/TitaniumKit/TitaniumKit/Sources/API/TiUIView.m, the -borderLayer method (lines 626-645) is asymmetric.

The array → scalar transition (lines 630-636) tears down _borderLayer and restores self.layer.borderWidth from the shape layer's lineWidth:

self.layer.mask = nil;
self.layer.borderColor = _borderLayer.strokeColor;
self.layer.borderWidth = _borderLayer.lineWidth / 2;
[_borderLayer removeFromSuperlayer];
RELEASE_TO_NIL(_borderLayer);
_borderLayer = (CAShapeLayer *)self.layer;

The scalar → array transition (lines 637-642) creates a new CAShapeLayer with lineWidth = self.layer.borderWidth * 2 (centered-stroke compensation), but does not clear self.layer.borderWidth or self.layer.borderColor:

_borderLayer = [[CAShapeLayer alloc] init];
_borderLayer.fillColor = UIColor.clearColor.CGColor;
_borderLayer.strokeColor = self.layer.borderColor;
_borderLayer.lineWidth = self.layer.borderWidth * 2;
[self.layer addSublayer:_borderLayer];

For the typical TSS application order (borderWidth applied before borderRadius):

1. setBorderWidth_: runs first. borderRadius is not yet on the proxy, so borderLayer returns self.layer. self.layer.borderWidth = 4.
2. setBorderRadius_: runs. array.count = 4, so borderLayer enters the else if branch and creates a separate CAShapeLayer with lineWidth = 8. self.layer.borderWidth is left at 4.
3. updateBorderRadius: applies the per-corner mask via addCornerRadius:toLayer:.

Two borders render at the same time:

• self.layer.borderWidth = 4 (native CALayer border, clipped by the per-corner mask) → 4dp visible.
• _borderLayer stroke with lineWidth = 8, inner half visible after the mask → 4dp visible.

Total: 8dp = twice the declared borderWidth: 4.

Proposed fix

Reset the native border on self.layer when promoting to a separate CAShapeLayer:

 } else if ((array.count > 1) && (!_borderLayer || _borderLayer == self.layer)) {
   _borderLayer = [[CAShapeLayer alloc] init];
   _borderLayer.fillColor = UIColor.clearColor.CGColor;
   _borderLayer.strokeColor = self.layer.borderColor;
   _borderLayer.lineWidth = self.layer.borderWidth * 2;
+  self.layer.borderColor = nil;
+  self.layer.borderWidth = 0;
   [self.layer addSublayer:_borderLayer];
 }

This makes the scalar-to-array transition symmetric to the existing array-to-scalar handling.

Environment

• Platform: iOS simulator (iPhone 17e), also reproduces on device
• Titanium SDK: 13.2.0.GA
• Code analyzed against main at commit 48d5761 (borderLayer unchanged in recent history)