VerticalTextView XML / View implementation for androidx.text.vertical 1.0.0-alpha01

VerticalTextView.kt

package dev.spght.example.text

import android.content.Context
import android.graphics.Canvas
import android.text.Spanned
import android.text.TextPaint
import android.util.AttributeSet
import android.view.View
import androidx.text.vertical.VerticalTextLayout

open class VerticalTextView @JvmOverloads constructor(
    context: Context,
    attrs: AttributeSet? = null,
    defStyleAttr: Int = 0,
    defStyleRes: Int = 0
) : View(context, attrs, defStyleAttr, defStyleRes) {

    private var textLayout: VerticalTextLayout? = null
    private var pendingText: Spanned? = null
    private var pendingPaint: TextPaint? = null

    override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
        super.onSizeChanged(w, h, oldw, oldh)
        val text = pendingText ?: return
        val paint = pendingPaint ?: return
        textLayout = generateLayout(
            text = text,
            paint = paint,
            height = h.toFloat()
        )

    }

    override fun onDraw(canvas: Canvas) {
        textLayout?.draw(canvas, width.toFloat(), 0.0f)
    }

    fun setText(text: Spanned, paint: TextPaint) {
        pendingText = text
        pendingPaint = paint
        requestLayout()
    }

    private fun generateLayout(
        text: Spanned,
        paint: TextPaint,
        height: Float,
    ) = VerticalTextLayout.Builder(
        text = text,
        start = 0,
        end = text.length,
        paint = paint,
        height = height,
    ).build()

}