byre/mac/Sources/Byre/Diagram.swift

import AppKit
import CoreText
import SwiftUI

struct DiagramError: Error {
    let reason: String
}

func textSize(_ text: String, _ font: CTFont) -> CGSize {
    let lines = text.components(separatedBy: "\n")
    var width: CGFloat = 0
    for l in lines {
        let line = CTLineCreateWithAttributedString(NSAttributedString(string: l, attributes: [.font: font as NSFont]))
        width = max(width, CGFloat(CTLineGetTypographicBounds(line, nil, nil, nil)))
    }
    let lineHeight = CTFontGetAscent(font) + CTFontGetDescent(font) + CTFontGetLeading(font) + 3
    return CGSize(width: ceil(width), height: ceil(lineHeight * CGFloat(lines.count)))
}

struct DiagramFailure: View {
    let source: String
    let reason: String

    var body: some View {
        VStack(alignment: .leading, spacing: 4) {
            Text(verbatim: source)
                .textSelection(.enabled)
                .padding(.horizontal, 8)
                .padding(.vertical, 6)
                .frame(maxWidth: .infinity, alignment: .leading)
                .background(Palette.surface, in: RoundedRectangle(cornerRadius: 6))
            Text(verbatim: "diagram not rendered: \(reason)")
                .foregroundStyle(Palette.muted)
        }
    }
}