fix: interpolate without mirroring the ends when infinite scroll is off

src/hooks/useInterpolateInsideCarousel.ts

@@ -8,9 +8,15 @@ export const useInterpolateInsideCarousel = (values: {
   valueAfter: number
   offset?: number
 }) => {
-  const { scrollValue } = useCarouselContext()
+  const { scrollValue, disableInfiniteScroll } = useCarouselContext()
   const { index, total } = useAutoCarouselSlideIndex()
   return useDerivedValue(() => {
-    return interpolateInsideCarousel(scrollValue.value, index, total, values)
-  }, [scrollValue, values])
+    return interpolateInsideCarousel(
+      scrollValue.value,
+      index,
+      total,
+      values,
+      !disableInfiniteScroll,
+    )
+  }, [scrollValue, values, disableInfiniteScroll])
 }

src/utils/__tests__/interpolateInsideCarousel.test.ts

@@ -300,4 +300,30 @@ describe('interpolateInsideCarousel', () => {
     })
     expect(result).toBe(1)
   })
+
+  describe('without infinite scroll', () => {
+    // Three real slides and no clones, so the ends don't mirror each other.
+    const values = { valueBefore: 0, thisValue: 1, valueAfter: 0 }
+
+    it('keeps the first slide at the side value while the second is current', () => {
+      expect(interpolateInsideCarousel(1, 0, 3, values, false)).toBe(0)
+    })
+
+    it('keeps the second slide at the side value while the last is current', () => {
+      expect(interpolateInsideCarousel(2, 1, 3, values, false)).toBe(0)
+    })
+
+    it('keeps the last slide at the side value while the second is current', () => {
+      expect(interpolateInsideCarousel(1, 2, 3, values, false)).toBe(0)
+    })
+
+    it('gives the current slide its own value', () => {
+      expect(interpolateInsideCarousel(0, 0, 3, values, false)).toBe(1)
+      expect(interpolateInsideCarousel(2, 2, 3, values, false)).toBe(1)
+    })
+
+    it('interpolates halfway between slides', () => {
+      expect(interpolateInsideCarousel(0.5, 0, 3, values, false)).toBe(0.5)
+    })
+  })
 })

src/utils/interpolateInsideCarousel.ts

@@ -10,6 +10,9 @@ export const interpolateInsideCarousel = (
     valueAfter: number
     offset?: number
   },
+  // With infinite scroll the first and last slides are clones, so a slide also counts as current
+  // while its clone is.
+  isInfinite = true,
 ) => {
   'worklet'
   const { valueBefore, thisValue, valueAfter, offset = 0 } = values
@@ -27,6 +30,7 @@ export const interpolateInsideCarousel = (
   }
 
   const getAdjustedIndex = (slideIndex: number) => {
+    if (!isInfinite) return slideIndex
     if (slideIndex === 0) return Math.max(totalLength - 2, 0)
     if (slideIndex === totalLength - 1) return 1
     if (slideIndex === 1) return totalLength - 1