Make Ruler look more like Xcode by creating custom font. Make ruler font and ruler Inset scale with text font size.

Package.swift

@@ -1,11 +1,11 @@
-// swift-tools-version: 5.6
+// swift-tools-version: 5.7
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription
 
 let package = Package(
     name: "CodeEditTextView",
-    platforms: [.macOS(.v12)],
+    platforms: [.macOS(.v13)],
     products: [
         .library(
             name: "CodeEditTextView",

Sources/CodeEditTextView/Controller/STTextViewController.swift

@@ -130,9 +130,9 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
         rulerView.textColor = .secondaryLabelColor
         rulerView.drawSeparator = false
         rulerView.baselineOffset = baselineOffset
-        rulerView.font = NSFont.monospacedDigitSystemFont(ofSize: 9.5, weight: .regular)
+        rulerView.font = rulerFont
         rulerView.selectedLineHighlightColor = theme.lineHighlight
-        rulerView.rulerInsets = STRulerInsets(leading: 20, trailing: 8)
+        rulerView.rulerInsets = STRulerInsets(leading: rulerFont.pointSize * 1.6, trailing: 8)
 
         if self.isEditable == false {
             rulerView.selectedLineTextColor = nil
@@ -255,6 +255,8 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
         rulerView?.selectedLineHighlightColor = theme.lineHighlight
         rulerView?.baselineOffset = baselineOffset
         rulerView.highlightSelectedLine = isEditable
+        rulerView?.rulerInsets = STRulerInsets(leading: rulerFont.pointSize * 1.6, trailing: 8)
+        rulerView?.font = rulerFont
 
         if let scrollView = view as? NSScrollView {
             scrollView.drawsBackground = useThemeBackground

Sources/CodeEditTextView/Extensions/NSFont+RulerFont.swift

@@ -0,0 +1,42 @@
+//
+//  NSFont+RulerFont.swift
+//  
+//
+//  Created by Elias Wahl on 17.03.23.
+//
+
+import Foundation
+import AppKit
+
+extension STTextViewController {
+    var rulerFont: NSFont {
+        let fontSize: Double = (font.pointSize - 1) + 0.25
+        let fontAdvance: Double = font.pointSize * 0.49 + 0.1
+        let fontWeight = NSFont.Weight(rawValue: font.pointSize * 0.00001 + 0.0001)
+        let fontWidth = NSFont.Width(rawValue: -0.13)
+
+        let font = NSFont.systemFont(ofSize: fontSize, weight: fontWeight, width: fontWidth)
+
+        /// Set the open four
+        let alt4: [NSFontDescriptor.FeatureKey: Int] = [
+            .selectorIdentifier: kStylisticAltOneOnSelector,
+            .typeIdentifier: kStylisticAlternativesType
+        ]
+
+        /// Set alternate styling for 6 and 9
+        let alt6and9: [NSFontDescriptor.FeatureKey: Int] = [
+            .selectorIdentifier: kStylisticAltTwoOnSelector,
+            .typeIdentifier: kStylisticAlternativesType
+        ]
+
+        /// Make all digits monospaced
+        let monoSpaceDigits: [NSFontDescriptor.FeatureKey: Int] = [
+            .selectorIdentifier: 0,
+            .typeIdentifier: kNumberSpacingType
+        ]
+
+        let features = [alt4, alt6and9, monoSpaceDigits]
+        let descriptor = font.fontDescriptor.addingAttributes([.featureSettings: features, .fixedAdvance: fontAdvance])
+        return NSFont(descriptor: descriptor, size: 0) ?? font
+    }
+}