---
title: "CTLineGetOffsetForStringIndex(_:_:_:)"
framework: coretext
role: symbol
role_heading: Function
path: "coretext/ctlinegetoffsetforstringindex(_:_:_:)"
---

# CTLineGetOffsetForStringIndex(_:_:_:)

Determines the graphical offset or offsets for a string index.

## Declaration

```swift
func CTLineGetOffsetForStringIndex(_ line: CTLine, _ charIndex: CFIndex, _ secondaryOffset: UnsafeMutablePointer<CGFloat>?) -> CGFloat
```

## Parameters

- `line`: The line from which the offset is requested.
- `charIndex`: The string index corresponding to the desired position.
- `secondaryOffset`: On output, the secondary offset along the baseline for charIndex. When a single caret is sufficient for a string index, this value will be the same as the primary offset, which is the return value of this function. May be NULL.

## Return Value

Return Value The primary offset along the baseline for charIndex, or 0.0 if the line does not support string access.

## Discussion

Discussion This function returns the graphical offset or offsets corresponding to a string index, suitable for movement between adjacent lines or for drawing a custom caret. For moving between adjacent lines, the primary offset can be adjusted for any relative indentation of the two lines; a CGPoint constructed with the adjusted offset for its x value and 0.0 for its y value is suitable for passing to CTLineGetStringIndexForPosition(_:_:). For drawing a custom caret, the returned primary offset corresponds to the portion of the caret that represents the visual insertion location for a character whose direction matches the line’s writing direction.

## See Also

### Getting Line Positioning

- [CTLineGetStringIndexForPosition(_:_:)](coretext/ctlinegetstringindexforposition(_:_:).md)
- [CTLineEnumerateCaretOffsets(_:_:)](coretext/ctlineenumeratecaretoffsets(_:_:).md)