Remove NSLayoutManager (CodeEditApp#112)

# Description

This PR removes all references to `NSLayoutManager` and fixes syntax
highlighting after the regression in CodeEditApp#105.

# Related Issues

N/A

# Checklist

- [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] My changes generate no new warnings
- [x] My code builds and runs on my machine
- [x] I documented my code
- [x] Review requested

Sources/CodeEditTextView/CodeEditTextView.swift

@@ -73,12 +73,19 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
 
     public func updateNSViewController(_ controller: NSViewControllerType, context: Context) {
         controller.font = font
-        controller.language = language
-        controller.theme = theme
         controller.tabWidth = tabWidth
         controller.wrapLines = wrapLines
         controller.lineHeightMultiple = lineHeight
         controller.editorOverscroll = editorOverscroll
+
+        // Updating the language and theme needlessly can cause highlights to be re-calculated.
+        if controller.language.id != language.id {
+            controller.language = language
+        }
+        if controller.theme != theme {
+            controller.theme = theme
+        }
+
         controller.reloadUI()
         return
     }

Sources/CodeEditTextView/Extensions/NSRange+/NSRange+NSTextRange.swift

@@ -21,4 +21,17 @@ public extension NSTextRange {
 
         self.init(location: start, end: end)
     }
+
+    /// Creates an `NSRange` using document information from the given provider.
+    /// - Parameter provider: The `NSTextElementProvider` to use to convert this range into an `NSRange`
+    /// - Returns: An `NSRange` if possible
+    func nsRange(using provider: NSTextElementProvider) -> NSRange? {
+        guard let location = provider.offset?(from: provider.documentRange.location, to: location) else {
+            return nil
+        }
+        guard let length = provider.offset?(from: self.location, to: endLocation) else {
+            return nil
+        }
+        return NSRange(location: location, length: length)
+    }
 }

Sources/CodeEditTextView/Extensions/STTextView+/STTextView+VisibleRange.swift

@@ -7,22 +7,32 @@
 
 import Foundation
 import STTextView
+import AppKit
 
 extension STTextView {
-    func textRange(for rect: CGRect) -> NSRange {
-        let length = self.textContentStorage.textStorage?.length ?? 0
+    /// A helper for calculating the visible range on the text view with some small vertical padding.
+    var visibleTextRange: NSRange? {
+        // This helper finds the visible rect of the text using the enclosing scroll view, then finds the nearest
+        // `NSTextElement`s to those points and uses those elements to create the returned range.
 
-        guard let layoutManager = self.textContainer.layoutManager else {
-            return NSRange(0..<length)
+        // Get visible rect
+        guard let bounds = enclosingScrollView?.documentVisibleRect else {
+            return textLayoutManager.documentRange.nsRange(using: textContentStorage)
         }
-        let container = self.textContainer
 
-        let glyphRange = layoutManager.glyphRange(forBoundingRect: rect, in: container)
+        // Calculate min & max points w/ a small amount of padding vertically.
+        let minPoint = CGPoint(x: bounds.minX,
+                               y: bounds.minY - 100)
+        let maxPoint = CGPoint(x: bounds.maxX,
+                               y: bounds.maxY + 100)
 
-        return layoutManager.characterRange(forGlyphRange: glyphRange, actualGlyphRange: nil)
-    }
+        // Get text fragments for both the min and max points
+        guard let start = textLayoutManager.textLayoutFragment(for: minPoint)?.rangeInElement.location,
+              let end = textLayoutManager.textLayoutFragment(for: maxPoint)?.rangeInElement.endLocation else {
+            return textLayoutManager.documentRange.nsRange(using: textContentStorage)
+        }
 
-    var visibleTextRange: NSRange {
-        return textRange(for: visibleRect)
+        // Calculate a range and return it as an `NSRange`
+        return NSTextRange(location: start, end: end)?.nsRange(using: textContentStorage)
     }
 }

Sources/CodeEditTextView/Highlighting/HighlightRange.swift

@@ -1,6 +1,6 @@
 //
 //  HighlightRange.swift
-//  
+//
 //
 //  Created by Khan Winter on 9/14/22.
 //

Sources/CodeEditTextView/Highlighting/Highlighter.swift

@@ -42,7 +42,10 @@ class Highlighter: NSObject {
 
     /// The set of visible indexes in tht text view
     lazy private var visibleSet: IndexSet = {
-        return IndexSet(integersIn: Range(textView.visibleTextRange)!)
+        guard let range = textView.visibleTextRange else {
+            return IndexSet()
+        }
+        return IndexSet(integersIn: Range(range)!)
     }()
 
     // MARK: - UI
@@ -184,6 +187,11 @@ private extension Highlighter {
             // Loop through each highlight and modify the textStorage accordingly.
             textView.textContentStorage.textStorage?.beginEditing()
             for highlight in highlightRanges {
+                // Does not work:
+//                textView.textLayoutManager.setRenderingAttributes(attributeProvider.attributesFor(highlight.capture),
+//                                                                  for: NSTextRange(highlight.range,
+//                                                                       provider: textView.textContentStorage)!)
+                // Temp solution (until Apple fixes above)
                 textView.textContentStorage.textStorage?.setAttributes(
                     attributeProvider.attributesFor(highlight.capture),
                     range: highlight.range
@@ -219,7 +227,7 @@ private extension Highlighter {
 private extension Highlighter {
     /// Updates the view to highlight newly visible text when the textview is scrolled or bounds change.
     @objc func visibleTextChanged(_ notification: Notification) {
-        visibleSet = IndexSet(integersIn: Range(textView.visibleTextRange)!)
+        visibleSet = IndexSet(integersIn: Range(textView.visibleTextRange ?? NSRange())!)
 
         // Any indices that are both *not* valid and in the visible text range should be invalidated
         let newlyInvalidSet = visibleSet.subtracting(validSet)