Make Ruler look more like Xcode by creating custom font. Make ruler font and ruler Inset scale with text font size. (#170)

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### Description

This PR adds a customized SF Pro Font which aims to look like the Xcode
Digits font.
The ruler font and the ruler insets scale with the text font size. 

### Related Issues

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<!--- If this PR resolves the issue please specify (e.g. * closes #123)
-->
<!--- If this PR addresses multiple issues, these issues must be related
to one other -->

* closes #58
* closes #157 

### Checklist

<!--- Add things that are not yet implemented above -->

- [x] I read and understood the [contributing
guide](https://github.com/CodeEditApp/CodeEdit/blob/main/CONTRIBUTING.md)
as well as the [code of
conduct](https://github.com/CodeEditApp/CodeEdit/blob/main/CODE_OF_CONDUCT.md)
- [x] The issues this PR addresses are related to each other
- [x] My changes generate no new warnings
- [x] My code builds and runs on my machine
- [x] My changes are all related to the related issue above
- [x] I documented my code

### Screenshots

<!--- REQUIRED: if issue is UI related -->
PointSize 13:
Xcode left, CodeEdit Right:
<img width="73" alt="image"
src="https://user-images.githubusercontent.com/82230675/227798735-1041b4a0-7aa9-4e3e-8c73-a8993427e862.png">

PointSize 20:
Xcode left, CodeEdit Right:
<img width="162" alt="image"
src="https://user-images.githubusercontent.com/82230675/227799017-87c08fb7-bac5-4a63-8fb2-b0bf4b0f3f0b.png">



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---------

Co-authored-by: Lukas Pistrol <l.pistrol@gmail.com>

Author: Eliulm

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
+    }
+}