Render font from command line on OS X without requiring font to be installed.

FontPreview.swift

//
// FontPreview
// Copyright © 2018 Leon Breedt
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
import AppKit
import WebKit
import Darwin

let kFontSampleBoxWidth = 400
let kFontSampleBoxSpacing = 5
let kDefaultFontSize: Float = 14.0
let kFontSampleText = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum."

class TextRendererView : NSView {
    let primaryFontFilePath: String
    let fontSize: Float
    let additionalFontFilePaths: [String]
    var pdfData: NSData?
    
    private var textFontsByFilePath: [String: CTFont]
    private var fontsByFilePath: [String: NSFont]
    
    init(frame: NSRect, primaryFontFilePath: String, fontSize: Float, additionalFontFilePaths: [String]) {
        self.primaryFontFilePath = primaryFontFilePath
        self.fontSize = fontSize
        self.additionalFontFilePaths = additionalFontFilePaths
        let allFontFilePaths = [primaryFontFilePath] + additionalFontFilePaths
        let textFontsByFilePath = Dictionary(uniqueKeysWithValues: zip(allFontFilePaths, allFontFilePaths.map { TextRendererView.loadFont($0, size: fontSize) }))
        self.fontsByFilePath = Dictionary(uniqueKeysWithValues: textFontsByFilePath.map { ($0.key, textFontsByFilePath[$0.key]! as NSFont) })
        self.textFontsByFilePath = textFontsByFilePath
        self.pdfData = nil
        
        super.init(frame: frame)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) not supported")
    }
    
    var text: String? {
        didSet {
            setNeedsDisplay(frame)
        }
    }
    
    override func draw(_ dirtyRect: NSRect) {
        let consumerData = NSMutableData()
        let consumer = CGDataConsumer(data: consumerData)!
        
        var rect = CGRect(x: dirtyRect.origin.x,
                          y: dirtyRect.origin.y,
                          width: dirtyRect.width,
                          height: dirtyRect.height)
        
        guard let context = CGContext(consumer: consumer, mediaBox: &rect, nil) else {
            fatalError("failed to create PDF context")
        }
        
        context.textMatrix = .identity
        context.beginPDFPage(nil)
        
        var boxLeft = kFontSampleBoxSpacing
        
        for filePath in [primaryFontFilePath] + additionalFontFilePaths {
            guard let font = fontsByFilePath[filePath] else {
                fatalError("failed to load font for \(filePath)")
            }
            
            print("drawing text with font: \(font.fontName)")
            let attributedString = NSAttributedString(string: text ?? "", attributes: [.font: font])
            
            let framesetter = CTFramesetterCreateWithAttributedString(attributedString)
            let path = CGMutablePath()
            let bounds = CGRect(x: boxLeft, y: 0, width: kFontSampleBoxWidth, height: 400)
            path.addRect(bounds)
            let frame = CTFramesetterCreateFrame(framesetter, CFRange(location: 0, length: 0), path, nil)
            
            CTFrameDraw(frame, context)
            
            boxLeft += kFontSampleBoxWidth + kFontSampleBoxSpacing
        }
        
        context.endPDFPage()
        context.closePDF()
        
        pdfData = consumerData
    }
    
    private static func loadFont(_ path: String, size: Float) -> CTFont {
        print("loading font \(path) using Core Text")
        guard let data = NSData(contentsOfFile: path) else {
            fatalError("failed to load font from \(path)")
        }
        
        guard let provider = CGDataProvider(data: data) else {
            fatalError("failed to create Core Graphs data provider for font data")
        }
        guard let font = CGFont(provider) else {
            fatalError("failed to create Core Graphics font")
        }
        
        var error: Unmanaged<CFError>?
        if !CTFontManagerRegisterGraphicsFont(font, &error) {
            fatalError("failed to register font: \(error!)")
        }
        
        return CTFontCreateWithGraphicsFont(font, CGFloat(size), nil, nil)
    }
}

// Application

let args = Array(CommandLine.arguments[1..<CommandLine.arguments.count])
if args.count < 3 {
    print("usage: FontPreview PDF-FILE-NAME FONT-SIZE FONT-FILE-PATH [COMPARE-FONT-FILE-PATH ...]")
    exit(1)
}

let (pdfFilePath, fontSize, primaryFontFilePath) =
    (args[0], Float(args[1]) ?? kDefaultFontSize, args[2])

let comparisonFontFilePaths: [String] =
    args.count > 3
        ? Array(args[3..<args.count])
        : []

let application = NSApplication.shared
let rect = NSRect(x: -1024, y: -1024, width: 1024, height: 1024)
let window = NSWindow(contentRect: rect,
                      styleMask: .borderless,
                      backing: .buffered,
                      defer: true)
window.makeKey()

let totalWidth = kFontSampleBoxSpacing + kFontSampleBoxWidth +
    (kFontSampleBoxWidth * comparisonFontFilePaths.count) +
    (kFontSampleBoxSpacing * comparisonFontFilePaths.count) +
kFontSampleBoxSpacing

let rendererFrame = NSRect(x: 0, y: 0, width: totalWidth, height: 400)
let rendererView = TextRendererView(frame: rendererFrame,
                                    primaryFontFilePath: primaryFontFilePath,
                                    fontSize: fontSize,
                                    additionalFontFilePaths: comparisonFontFilePaths)
rendererView.text = kFontSampleText
window.contentView!.addSubview(rendererView)

rendererView.draw(rendererFrame)

RunLoop.current.run(until: Date(timeIntervalSinceNow: 0.1))

if let data = rendererView.pdfData {
    data.write(toFile: pdfFilePath, atomically: true)
    print("rendered \(data.length) byte(s) to PDF file \(pdfFilePath)")
} else {
    fatalError("rendering did not occur")
}

Updated for Swift 4.1.