[Shapes] Updates the shapeGenerator with a line width to inset the li…

…ne rather than center it.

There is a visual difference when using lineWidth instead of borderWidth due to lineWidth drawing on the path, and borderWidth insetting from the path.
To resolve this, the path is made smaller by half the width of the line, thus to create a similar visual appearance as if borderWidth was set.

PiperOrigin-RevId: 322615641

components/Shapes/src/MDCShapedShadowLayer.m

@@ -104,9 +104,25 @@ - (void)setPath:(CGPathRef)path {
     _colorLayer.fillColor = self.shapedBackgroundColor.CGColor;
     _colorLayer.strokeColor = self.shapedBorderColor.CGColor;
     _colorLayer.lineWidth = self.shapedBorderWidth;
+    [self generateColorPathGivenLineWidth];
   }
 }
 
+- (void)generateColorPathGivenLineWidth {
+  if (CGPathIsEmpty(self.path) || _colorLayer.lineWidth <= 0) {
+    return;
+  }
+  CGFloat halfOfBorderWidth = self.shapedBorderWidth / 2.f;
+  CGRect standardizedBounds = CGRectStandardize(self.bounds);
+  CGRect insetBounds = CGRectInset(standardizedBounds, halfOfBorderWidth, halfOfBorderWidth);
+  CGAffineTransform transform =
+      CGAffineTransformMakeTranslation(halfOfBorderWidth, halfOfBorderWidth);
+  transform = CGAffineTransformScale(
+      transform, CGRectGetWidth(insetBounds) / CGRectGetWidth(standardizedBounds),
+      CGRectGetHeight(insetBounds) / CGRectGetHeight(standardizedBounds));
+  _colorLayer.path = CGPathCreateCopyByTransformingPath(_colorLayer.path, &transform);
+}
+
 - (CGPathRef)path {
   return _colorLayer.path;
 }
@@ -155,6 +171,7 @@ - (void)setShapedBorderWidth:(CGFloat)shapedBorderWidth {
   } else {
     self.borderWidth = 0;
     _colorLayer.lineWidth = _shapedBorderWidth;
+    [self generateColorPathGivenLineWidth];
   }
 }
 

components/Shapes/tests/snapshot/MDCShapedViewSnapshotTests.m

@@ -52,6 +52,37 @@ - (void)generateSnapshotAndVerifyView {
 
 #pragma mark - Tests
 
+- (void)testRectShapedViewWithCornerRadiusBySettingABorderWidthToPositiveThenZero {
+  // Given
+  MDCRectangleShapeGenerator *shapeGenerator = [[MDCRectangleShapeGenerator alloc] init];
+  MDCRoundedCornerTreatment *cornerTreatment = [MDCRoundedCornerTreatment cornerWithRadius:50.f];
+  [shapeGenerator setCorners:cornerTreatment];
+  ((MDCShapedShadowLayer *)self.shapedView.layer).shapedBorderWidth = 10;
+  ((MDCShapedShadowLayer *)self.shapedView.layer).shapedBorderColor = UIColor.redColor;
+
+  // When
+  self.shapedView.shapeGenerator = shapeGenerator;
+  ((MDCShapedShadowLayer *)self.shapedView.layer).shapedBorderWidth = 0;
+
+  // Then
+  [self generateSnapshotAndVerifyView];
+}
+
+- (void)testRectShapedViewWithCornerRadius {
+  // Given
+  MDCRectangleShapeGenerator *shapeGenerator = [[MDCRectangleShapeGenerator alloc] init];
+  MDCRoundedCornerTreatment *cornerTreatment = [MDCRoundedCornerTreatment cornerWithRadius:50.f];
+  [shapeGenerator setCorners:cornerTreatment];
+  ((MDCShapedShadowLayer *)self.shapedView.layer).shapedBorderWidth = 10;
+  ((MDCShapedShadowLayer *)self.shapedView.layer).shapedBorderColor = UIColor.redColor;
+
+  // When
+  self.shapedView.shapeGenerator = shapeGenerator;
+
+  // Then
+  [self generateSnapshotAndVerifyView];
+}
+
 - (void)testCurvedRectShapedViewElevation00 {
   // When
   self.shapedView.shapeGenerator =