SpannableStringBuilderでテキストをラベル化するときに使うSpan

LabelTextSpan.kt

class LabelTextSpan(
        @ColorInt private val labelColorInt: Int,
        @ColorInt private val textColorInt: Int,
        private val textSize: Float
) : ReplacementSpan() {

    override fun draw(
            canvas: Canvas,
            text: CharSequence?,
            start: Int,
            end: Int,
            x: Float,
            top: Int,
            y: Int,
            bottom: Int,
            paint: Paint
    ) {
        text ?: return
        canvas.save()
        paint.isAntiAlias = true
        paint.color = labelColorInt
        val backgroundWidth = getSize(paint, text, start, end, paint.fontMetricsInt).toFloat()
        val backgroundHeight = paint.descent() - paint.ascent()
        val backgroundRect = RectF(0f, 0f, backgroundWidth, backgroundHeight)
        canvas.translate(x, y + paint.ascent())
        canvas.drawRoundRect(backgroundRect, backgroundHeight, backgroundHeight, paint)

        val textRect = RectF(backgroundRect)
        paint.textSize = textSize
        paint.color = textColorInt
        textRect.right = paint.measureText(text, start, end)
        textRect.bottom = paint.descent() - paint.ascent()
        textRect.left += (backgroundRect.width() - textRect.right) / 2
        textRect.top += (backgroundRect.height() - textRect.bottom) / 2
        canvas.drawText(text, start, end, textRect.left, textRect.top - paint.ascent(), paint)
        canvas.restore()
    }

    override fun getSize(
            paint: Paint,
            text: CharSequence?,
            start: Int,
            end: Int,
            fm: Paint.FontMetricsInt?
    ): Int {
        Log.d("TextBackgroundSpan", "text=$text, start=$start, end=$end")
        text ?: return 0
        if (fm != null) {
            val pfm = paint.fontMetricsInt
            fm.ascent = pfm.ascent
            fm.descent = pfm.descent
            fm.top = pfm.top
            fm.bottom = pfm.bottom
        }
        val fa = FloatArray(end - start)
        paint.getTextWidths(text, start, end, fa)
        Log.d("TextBackgroundSpan", "text=$text, fa=${fa.toList()}")
        return fa.sum().toInt()
    }
}