How to display HTML using Android Compose

DefaultLinkMovementMethod.java

/**
 * Set this on a textview and then you can potentially open links locally if applicable
 */
public class DefaultLinkMovementMethod extends LinkMovementMethod {

    private OnLinkClickedListener mOnLinkClickedListener;

    public DefaultLinkMovementMethod(OnLinkClickedListener onLinkClickedListener) {
        mOnLinkClickedListener = onLinkClickedListener;
    }

    public boolean onTouchEvent(TextView widget, android.text.Spannable buffer, android.view.MotionEvent event) {
        int action = event.getAction();

        //http://stackoverflow.com/questions/1697084/handle-textview-link-click-in-my-android-app
        if (action == MotionEvent.ACTION_UP) {
            int x = (int) event.getX();
            int y = (int) event.getY();

            x -= widget.getTotalPaddingLeft();
            y -= widget.getTotalPaddingTop();

            x += widget.getScrollX();
            y += widget.getScrollY();

            Layout layout = widget.getLayout();
            int line = layout.getLineForVertical(y);
            int off = layout.getOffsetForHorizontal(line, x);

            URLSpan[] link = buffer.getSpans(off, off, URLSpan.class);
            if (link.length != 0) {
                String url = link[0].getURL();
                boolean handled = mOnLinkClickedListener.onLinkClicked(url);
                if (handled) {
                    return true;
                }
                return super.onTouchEvent(widget, buffer, event);
            }
        }
        return super.onTouchEvent(widget, buffer, event);
    }

    public interface OnLinkClickedListener {
        boolean onLinkClicked(String url);
    }
}

FromHtml.kt

fun fromHtml(context: Context, html: String): Spannable = parse(html).apply {
    removeLinksUnderline()
    styleBold(context)
}

private fun parse(html: String): Spannable =
    (HtmlCompat.fromHtml(html, HtmlCompat.FROM_HTML_MODE_COMPACT) as Spannable)

private fun Spannable.removeLinksUnderline() {
    for (s in getSpans(0, length, URLSpan::class.java)) {
        setSpan(object : UnderlineSpan() {
            override fun updateDrawState(tp: TextPaint) {
                tp.isUnderlineText = false
            }
        }, getSpanStart(s), getSpanEnd(s), 0)
    }
}

private fun Spannable.styleBold(context: Context) {
    val bold = ResourcesCompat.getFont(context, R.font.inter_medium)!!
    for (s in getSpans(0, length, StyleSpan::class.java)) {
        if (s.style == Typeface.BOLD) {
            setSpan(ForegroundColorSpan(Color.BLACK), getSpanStart(s), getSpanEnd(s), 0)
            setSpan(bold.getTypefaceSpan(), getSpanStart(s), getSpanEnd(s), 0)
        }
    }
}

HtmlText.kt

private const val LINK_1 = "link_1"
private const val LINK_2 = "link_2"
private const val SPACING_FIX = 3f

@Composable
fun HtmlText(
    modifier: Modifier = Modifier,
    html: String,
    textStyle: TextStyle = Typography.body1,
    onLink1Clicked: (() -> Unit)? = null,
    onLink2Clicked: (() -> Unit)? = null
) {
    AndroidView(
        modifier = modifier,
        update = { it.text = fromHtml(it.context, html) },
        factory = { context ->
            val spacingReady =
                max(textStyle.lineHeight.value - textStyle.fontSize.value - SPACING_FIX, 0f)
            val extraSpacing = spToPx(spacingReady.toInt(), context)
            val gravity = when (textStyle.textAlign) {
                TextAlign.Center -> Gravity.CENTER
                TextAlign.End -> Gravity.END
                else -> Gravity.START
            }
            val fontResId = when (textStyle.fontWeight) {
                FontWeight.Medium -> R.font.inter_medium
                else -> R.font.inter_regular
            }
            val font = ResourcesCompat.getFont(context, fontResId)

            TextView(context).apply {
                // general style
                textSize = textStyle.fontSize.value
                setLineSpacing(extraSpacing, 1f)
                setTextColor(textStyle.color.toArgb())
                setGravity(gravity)
                typeface = font
                // links
                setLinkTextColor(Primary.toArgb())
                movementMethod = DefaultLinkMovementMethod() { link ->
                    when (link) {
                        LINK_1 -> onLink1Clicked?.invoke()
                        LINK_2 -> onLink2Clicked?.invoke()                   
                    }
                    true
                }
            }
        }
    )
}

fun spToPx(sp: Int, context: Context): Float =
    TypedValue.applyDimension(
        TypedValue.COMPLEX_UNIT_SP,
        sp.toFloat(),
        context.resources.displayMetrics
    )

TypefaceSpanCompat.kt

fun Typeface.getTypefaceSpan(): MetricAffectingSpan =
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
        typefaceSpanCompatV28(this)
    } else {
        CustomTypefaceSpan(this)
    }

@TargetApi(Build.VERSION_CODES.P)
private fun typefaceSpanCompatV28(typeface: Typeface) = TypefaceSpan(typeface)

private class CustomTypefaceSpan(private val typeface: Typeface?) : MetricAffectingSpan() {

    override fun updateDrawState(paint: TextPaint) {
        paint.typeface = typeface
    }

    override fun updateMeasureState(paint: TextPaint) {
        paint.typeface = typeface
    }
}