RoundedBackgroundColorSpan.kt

override fun drawBackground(
    c: Canvas,
    p: Paint,
    left: Int,
    right: Int,
    top: Int,
    baseline: Int,
    bottom: Int,
    text: CharSequence,
    start: Int,
    end: Int,
    lnum: Int
) {

    val actualWidth = p.measureText(text, start, end) + 2f * padding

    val width = if (lnum == 0) {
        actualWidth
    } else if ((actualWidth < prevWidth) && (abs(prevWidth - actualWidth) < 2f * radius)) {
        prevWidth
    } else if ((actualWidth > prevWidth) && (abs(prevWidth - actualWidth) < 2f * radius)) {
        actualWidth + (2f * radius - abs(prevWidth - actualWidth))
    } else {
        actualWidth
    }

    val shiftLeft = 0f - padding
    val shiftRight = width + shiftLeft

    rect.set(shiftLeft, top.toFloat(), shiftRight, bottom.toFloat())

    c.drawRoundRect(rect, radius, radius, paint)

    if (lnum > 0) {
        drawCornerType1(c, path, rect, radius)

        when {
            prevWidth < width -> drawCornerType2(c, path, rect, radius)
            prevWidth > width -> drawCornerType3(c, path, rect, radius)
            else -> drawCornerType4(c, path, rect, radius)
        }
    }

    prevWidth = width
    prevLeft = rect.left
    prevRight = rect.right
    prevBottom = rect.bottom
    prevTop = rect.top
}