LabelLayoutModifier which adjusts Android text placement to match Figma text placement

LabelLayoutModifier.kt

public class LabelLayoutModifier(
    val context: Context,
    val lineHeight: TextUnit,
    val style: MyTextStyle,
) : LayoutModifier {

    override fun MeasureScope.measure(
        measurable: Measurable,
        constraints: Constraints
    ): MeasureResult {
        val placeable = measurable.measure(constraints)
        val lineCount = lineCount(placeable)
        val fullHeight = (lineHeight.toPx() * lineCount).roundToInt()
        val fontMetrics = fontMetrics(context, style)
        val centerOffset = floor((lineHeight.toPx().toDp() - fontMetrics.descent.toDp() + fontMetrics.ascent.toDp()).value / 2f).dp.toPx().toInt()
        val figmaOffset = fontMetrics.ascent - fontMetrics.top
        return layout(width = placeable.width, height = fullHeight) {
            // Alignment lines are recorded with the parents automatically.
            placeable.placeRelative(
                x = 0,
                y = (centerOffset - figmaOffset).toInt()
            )
        }
    }

    override fun IntrinsicMeasureScope.maxIntrinsicHeight(
        measurable: IntrinsicMeasurable,
        width: Int
    ): Int {
        return ceilToLineHeight(measurable.maxIntrinsicHeight(width))
    }

    override fun IntrinsicMeasureScope.minIntrinsicHeight(
        measurable: IntrinsicMeasurable,
        width: Int
    ): Int {
        return ceilToLineHeight(measurable.minIntrinsicHeight(width))
    }

    override fun IntrinsicMeasureScope.minIntrinsicWidth(
        measurable: IntrinsicMeasurable,
        height: Int
    ): Int {
        return measurable.minIntrinsicWidth(height)
    }

    override fun IntrinsicMeasureScope.maxIntrinsicWidth(
        measurable: IntrinsicMeasurable,
        height: Int
    ): Int {
        return measurable.maxIntrinsicWidth(height)
    }

    private fun Density.lineCount(placeable: Placeable): Int {
        val firstToLast = (placeable[LastBaseline] - placeable[FirstBaseline]).toFloat()
        return (firstToLast / lineHeight.toPx()).roundToInt() + 1
    }
    private fun Density.ceilToLineHeight(value: Int): Int {
        val lineHeightPx = lineHeight.toPx()
        return (ceil(value.toFloat() / lineHeightPx) * lineHeightPx).roundToInt()
    }
}

private fun Density.fontMetrics(context: Context, textStyle: MyTextStyle): Paint.FontMetrics {
    val fontResourceId = textStyle.fonts[textStyle.fontWeight]!!
    val font = ResourcesCompat.getFont(context, fontResourceId)
    val paint = Paint().also {
        it.typeface = font
        it.textSize = textStyle.fontSize.toPx()
    }

    return paint.fontMetrics
}

MyTextStyle.kt

public data class MyTextStyle internal constructor(
    val fontSize: TextUnit,
    val fontWeight: FontWeight,
    val letterSpacing: TextUnit,
    val lineHeight: TextUnit,
) {

    public val fonts: Map<FontWeight, Int> = mapOf(
        WaveFontWeight.Demi.fontWeight to R.font.nationale_demi_bold,
        WaveFontWeight.Bold.fontWeight to R.font.nationale_bold,
    )

    private val fontFamily: FontFamily = FontFamily(
        fonts.map { Font(it.value, it.key) }
    )

    internal fun asTextStyle(): TextStyle {
        return TextStyle(
            fontSize = fontSize,
            fontWeight = fontWeight,
            fontFamily = fontFamily,
            letterSpacing = letterSpacing,
            lineHeight = lineHeight,
        )
    }
}

Our font has a default line height which is 1.2 times the font size. For example, if the font size is 24px, the default line height would be 28.8px. According to the Figma design, the designer requires a consistent line height of 24px matching the font size of 24px.

In Compose/Android, it's feasible to increase the line height from the default font specification but not reduce it.

Any idea how to achieve this?

Reducing should be just as possible as reducing it. I would highly recommend to not use lineheight equal to the font size though, this is a common design mistake that does not take into account ascending and descending glyphs in the font.

You can read up on the space that fonts take up here: https://dev.to/canyudev/android-and-figma-typography-and-how-to-achieve-100-fidelity-l40

(ignore the calculations, these are pre-Compose-change)

Thanks. You mean, Reducing should be just as possible as increasing it?

Sorry for not getting back to you: Yes, that's aboslutely what i meant.