Text area drawing mechanism + font scaling into bounding box

TextAreaDrawer.kt

import lt.ito.export.TextAreaLineCounter
import sun.font.FontDesignMetrics
import java.awt.Font
import java.awt.FontMetrics
import java.awt.Graphics

/**
 * Scales font into bounding [boxWidth], [boxHeight] to fit in and draws it using word wrap
 */
class TextAreaScaleDrawer(
    private val text: String,
    private val maxFontSize: Int,
    private val boxHeight: Double,
    private val boxWidth: Double
) {

    private var _font: Font = Font(null, Font.LAYOUT_LEFT_TO_RIGHT, maxFontSize)

    val font: Font
        get() = _font

    fun draw(graphics: Graphics) {
        val scaleWrapResult = scaleFontToFit(
            maxFontSize = maxFontSize
        )
        graphics.font = scaleWrapResult.font
        val wrapTexts = scaleWrapResult
            .paragraph
            .sentences
            .flatMap { it.wraps }
            .map { it.wrapText }
        val nextLineStep = graphics.fontMetrics.height
        var yNextLine = nextLineStep
        wrapTexts.forEach { text ->
            graphics.drawString(text, 0, yNextLine)
            yNextLine += nextLineStep
        }
    }

    /**
     * Shrinks font size to fit in this text area
     */
    private fun scaleFontToFit(
        maxFontSize: Int
    ): ScaleWrapResult {
        val maxHeight = boxHeight
        val lineCounter = TextAreaLineCounter(textProvider)
        var textSize = maxFontSize
        var font = newFontWithSize(textSize)
        var fm = newFontMetrics(font)
        var paragraph = lineCounter.parseParagraph(font, fm)
        var textHeight = newTextHeight(fm, paragraph)
        while (textHeight > maxHeight) {
            textSize -= 1
            font = newFontWithSize(textSize)
            fm = newFontMetrics(font)
            paragraph = lineCounter.parseParagraph(font, fm)
            textHeight = newTextHeight(fm, paragraph)
        }

        // For easier text debugging
        // TextAreaLineCounter.l.debug("LC:lineCount(${paragraph.lineCount()}:${paragraph})/${this.text.inShort()}")
        return ScaleWrapResult(font, paragraph)
    }

    /**
     * Sometimes 'feet' are cut off when comparing text.
     * So we're giving a bit more 'room', for the feed to be drawn with extra [DEFAULT_EXTRA_TEXT_HEIGHT_COEFFICIENT]
     */
    private fun newTextHeight(
        fm: FontMetrics,
        paragraph: TextAreaLineCounter.WrappedParagraph
    ): Double {
        return paragraph.lineCount() * (fm.height * DEFAULT_EXTRA_TEXT_HEIGHT_COEFFICIENT)
    }

    private fun newFontWithSize(size: Int): Font {
        return Font(_font.name, _font.style, size)
    }

    private fun newFontMetrics(font: Font): FontMetrics {
        return FontDesignMetrics.getMetrics(font)
    }

    private class ScaleWrapResult(
        val font: Font,
        val paragraph: TextAreaLineCounter.WrappedParagraph
    )

    private val textProvider = object : TextAreaLineCounter.TextProvider {
        override val text: String = this@TextAreaScaleDrawer.text
        override val formatWidth: Float = boxWidth.toFloat()
    }

    companion object {
        const val DEFAULT_EXTRA_TEXT_HEIGHT_COEFFICIENT = 1.02
    }
}