Calculate letter spacing in Jetpack Compose

Question

How can I calculate letter spacing depending on the width of the device for a BasicTextField, limiting the number of characters (in my case 8) and the text is to occupy the whole available space?

I tried with the below code but the measured width doesn't seem to return the correct value every single time

     var actualTextViewWidth by remember { mutableIntStateOf(0) }
     BasicTextField(
          modifier =
              modifier.fillMaxWidth().onGloballyPositioned {
                  layoutCoordinates ->
                actualTextViewWidth = layoutCoordinates.size.width
              },
          value = enteredText,
          textStyle =
              TextStyle(
                  letterSpacing =
                      calculateLetterSpacing(actualTextViewWidth, 8).dpToSp,...


    fun calculateLetterSpacing(viewWidth: Int, maxCharacters: Int): Int {
        val targetTextWidth = viewWidth / (maxCharacters - 1)
    return targetTextWidth / (maxCharacters - 1)
}

Answer 1

You are only calculating the letter spacing. TextField has letters as well as spaces between letters.

@Composable
fun MonoSpacedTextFieldSample(
    maxCharCount: Int = 8,
) {
    val density = LocalDensity.current
    val textMeasurer = rememberTextMeasurer()
    var text by remember {
        mutableStateOf("")
    }
    var textFieldWidth by remember {
        mutableIntStateOf(0)
    }
    val textWidth = remember(text) {
        textMeasurer.measure(text).size.width
    }
    val letterSpacing = remember(textFieldWidth, textWidth) {
        with(density) {
            ((textFieldWidth - textWidth) / (maxCharCount)).toSp()
        }
    }

    BasicTextField(
        modifier = Modifier
            .background(Color.LightGray)
            .fillMaxWidth()
            .onSizeChanged {
                if (textFieldWidth != it.width) {
                    textFieldWidth = it.width
                }
            },
        value = text,
        onValueChange = {
            text = it
        },
        textStyle = TextStyle(
            letterSpacing = letterSpacing,
        )
    )
}

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Note: Make sure to pass the text style to rememberTextMeasurer() as well if you change any style aspects like font size.