FontのMetricsを可視化するため雑につくったReplacementSpan

FontMetricsSpan.kt

class FontMetricsSpan : ReplacementSpan() {

    override fun draw(
            canvas: Canvas,
            text: CharSequence?,
            start: Int,
            end: Int,
            x: Float,
            top: Int,
            y: Int,
            bottom: Int,
            paint: Paint
    ) {
        canvas.save()
        val fontAscent = paint.fontMetricsInt.ascent
        val fontDescent = paint.fontMetricsInt.descent
        Log.d("FontMetricsSpan", "fontAscent=$fontAscent, fontDescent=$fontDescent, y=$y, top=$top")
        canvas.drawLine(y, Color.RED)
        canvas.drawLine(top, Color.BLUE)
        canvas.translate(0f, y.toFloat())
        canvas.drawLine(fontAscent / 2, Color.CYAN)
        canvas.drawLine(fontAscent, Color.GREEN)
        canvas.drawLine(fontDescent, Color.MAGENTA)
        canvas.restore()
    }

    private fun Canvas.drawLine(y: Int, colorInt: Int) {
        val paint = Paint().apply {
            strokeWidth = 1f
            color = colorInt
        }
        drawLine(0f, y.toFloat(), width.toFloat(), y.toFloat(), paint)
    }

    override fun getSize(
            paint: Paint,
            text: CharSequence?,
            start: Int,
            end: Int,
            fm: Paint.FontMetricsInt?
    ): Int {
        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(text.length)
        paint.getTextWidths(text, 0, text.length, fa)
        return fa.max()?.toInt() ?: 0
    }
}