From dc80f9b94763851dbd24f91a28a5f6962004a139 Mon Sep 17 00:00:00 2001
From: Khan Winter <35942988+thecoolwinter@users.noreply.github.com>
Date: Wed, 3 May 2023 16:13:36 -0500
Subject: [PATCH 1/7] Add brace pair highlighting

---
 .../CodeEditTextView/CodeEditTextView.swift   |  14 +-
 .../STTextViewController+HighlightRange.swift | 215 ++++++++++++++++++
 .../STTextViewController+Lifecycle.swift      | 144 ++++++++++++
 .../Controller/STTextViewController.swift     | 153 ++-----------
 .../Enums/BracePairHighlight.swift            |  18 ++
 .../STTextViewController+TextFormation.swift  |  20 +-
 .../TreeSitter/TreeSitterClient+Edit.swift    |   8 +-
 .../STTextViewControllerTests.swift           |  63 +++++
 8 files changed, 490 insertions(+), 145 deletions(-)
 create mode 100644 Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift
 create mode 100644 Sources/CodeEditTextView/Controller/STTextViewController+Lifecycle.swift
 create mode 100644 Sources/CodeEditTextView/Enums/BracePairHighlight.swift

diff --git a/Sources/CodeEditTextView/CodeEditTextView.swift b/Sources/CodeEditTextView/CodeEditTextView.swift
index 4dc39dd74..c340f42ce 100644
--- a/Sources/CodeEditTextView/CodeEditTextView.swift
+++ b/Sources/CodeEditTextView/CodeEditTextView.swift
@@ -33,6 +33,8 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
     ///   - isEditable: A Boolean value that controls whether the text view allows the user to edit text.
     ///   - letterSpacing: The amount of space to use between letters, as a percent. Eg: `1.0` = no space, `1.5` = 1/2 a
     ///                    character's width between characters, etc. Defaults to `1.0`
+    ///   - bracePairHighlight: The type of highlight to use to highlight brace pairs.
+    ///                         See `BracePairHighlight` for more information.
     public init(
         _ text: Binding<String>,
         language: CodeLanguage,
@@ -48,7 +50,8 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
         highlightProvider: HighlightProviding? = nil,
         contentInsets: NSEdgeInsets? = nil,
         isEditable: Bool = true,
-        letterSpacing: Double = 1.0
+        letterSpacing: Double = 1.0,
+        bracePairHighlight: BracePairHighlight? = nil
     ) {
         self._text = text
         self.language = language
@@ -65,6 +68,7 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
         self.contentInsets = contentInsets
         self.isEditable = isEditable
         self.letterSpacing = letterSpacing
+        self.bracePairHighlight = bracePairHighlight
     }
 
     @Binding private var text: String
@@ -82,6 +86,7 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
     private var contentInsets: NSEdgeInsets?
     private var isEditable: Bool
     private var letterSpacing: Double
+    private var bracePairHighlight: BracePairHighlight?
 
     public typealias NSViewControllerType = STTextViewController
 
@@ -101,7 +106,8 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
             highlightProvider: highlightProvider,
             contentInsets: contentInsets,
             isEditable: isEditable,
-            letterSpacing: letterSpacing
+            letterSpacing: letterSpacing,
+            bracePairHighlight: bracePairHighlight
         )
         return controller
     }
@@ -119,6 +125,7 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
         controller.lineHeightMultiple = lineHeight
         controller.editorOverscroll = editorOverscroll
         controller.contentInsets = contentInsets
+        controller.bracePairHighlight = bracePairHighlight
 
         // Updating the language, theme, tab width and indent option needlessly can cause highlights to be re-calculated
         if controller.language.id != language.id {
@@ -152,6 +159,7 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
         controller.theme == theme &&
         controller.indentOption == indentOption &&
         controller.tabWidth == tabWidth &&
-        controller.letterSpacing == letterSpacing
+        controller.letterSpacing == letterSpacing &&
+        controller.bracePairHighlight == bracePairHighlight
     }
 }
diff --git a/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift b/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift
new file mode 100644
index 000000000..7ac49de1c
--- /dev/null
+++ b/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift
@@ -0,0 +1,215 @@
+//
+//  STTextViewController+HighlightRange.swift
+//  CodeEditTextView
+//
+//  Created by Khan Winter on 4/26/23.
+//
+
+import AppKit
+import STTextView
+
+extension STTextViewController {
+    /// Highlights brace pairs using the current selection.
+    internal func highlightSelectionPairs() {
+        guard bracePairHighlight != nil else { return }
+        for selection in textView.textLayoutManager.textSelections.flatMap(\.textRanges) {
+            if selection.isEmpty,
+               let range = selection.nsRange(using: textView.textContentManager),
+               range.location > 0, // Range is not the beginning of the document
+               let preceedingCharacter = textView.textContentStorage?.textStorage?.substring(
+                from: NSRange(location: range.location - 1, length: 1) // The preceeding character exists
+               ) {
+                for pair in BracePairs.allValues {
+                    if preceedingCharacter == pair.0 {
+                        // Walk forwards
+                        if let characterIndex = findClosingPair(
+                            pair.0,
+                            pair.1,
+                            from: range.location,
+                            limit: min(NSMaxRange(textView.visibleTextRange ?? .zero) + 4096,
+                                       NSMaxRange(textView.documentRange)),
+                            reverse: false
+                        ) {
+                            highlightRange(NSRange(location: characterIndex, length: 1))
+                            if bracePairHighlight == .box {
+                                highlightRange(NSRange(location: range.location - 1, length: 1))
+                            }
+                        }
+                    } else if preceedingCharacter == pair.1 && range.location - 1 > 0 {
+                        // Walk backwards
+                        if let characterIndex = findClosingPair(
+                            pair.1,
+                            pair.0,
+                            from: range.location - 1,
+                            limit: max((textView.visibleTextRange?.location ?? 0) - 4096,
+                                       textView.documentRange.location),
+                            reverse: true
+                        ) {
+                            highlightRange(NSRange(location: characterIndex, length: 1))
+                            if bracePairHighlight == .box {
+                                highlightRange(NSRange(location: range.location - 1, length: 1))
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    /// Finds a closing character given a pair of characters, ignores pairs inside the given pair.
+    ///
+    /// ```pseudocode
+    /// { -- Start
+    ///   {
+    ///   } -- A naive algorithm may find this character as the closing pair, which would be incorrect.
+    /// } -- Found
+    /// ```
+    /// - Parameters:
+    ///   - open: The opening pair to look for.
+    ///   - close: The closing pair to look for.
+    ///   - from: The index to start from. This should not include the start character. Eg given `"{ }"` looking forward
+    ///           the index should be `1`
+    ///   - limit: A limiting index to stop at. When `reverse` is `true`, this is the minimum index. When `false` this
+    ///            is the maximum index.
+    ///   - reverse: Set to `true` to walk backwards from `from`.
+    /// - Returns: The index of the found closing pair, if any.
+    internal func findClosingPair(_ close: String, _ open: String, from: Int, limit: Int, reverse: Bool) -> Int? {
+        // Walk the text, counting each close. When we find an open that makes closeCount < 0, return that index.
+        var options: NSString.EnumerationOptions = .byCaretPositions
+        if reverse {
+            options = options.union(.reverse)
+        }
+        var closeCount = 0
+        var index: Int?
+        textView.textContentStorage?.textStorage?.mutableString.enumerateSubstrings(
+            in: reverse ?
+                NSRange(location: limit, length: from - limit) :
+                NSRange(location: from, length: limit - from),
+            options: options,
+            using: { substring, range, _, stop in
+                if substring == close {
+                    closeCount += 1
+                } else if substring == open {
+                    closeCount -= 1
+                }
+
+                if closeCount < 0 {
+                    index = range.location
+                    stop.pointee = true
+                }
+            }
+        )
+        return index
+    }
+
+    /// Adds a temporary highlight effect to the given range.
+    /// - Parameters:
+    ///   - range: The range to highlight
+    ///   - scrollToRange: Set to true to scroll to the given range when highlighting. Defaults to `false`.
+    public func highlightRange(_ range: NSTextRange, scrollToRange: Bool = false) {
+        guard let bracePairHighlight = bracePairHighlight,
+              var rectToHighlight = textView.textLayoutManager.textSelectionSegmentFrame(
+                in: range, type: .highlight
+        ) else {
+            return
+        }
+        let layer = CAShapeLayer()
+
+        switch bracePairHighlight {
+        case .flash:
+            rectToHighlight.size.width += 4
+            rectToHighlight.origin.x -= 2
+
+            layer.cornerRadius = 3.0
+            layer.backgroundColor = NSColor(hex: 0xFEFA80, alpha: 1.0).cgColor
+            layer.shadowColor = .black
+            layer.shadowOpacity = 0.3
+            layer.shadowOffset = CGSize(width: 0, height: 1)
+            layer.shadowRadius = 3.0
+            layer.opacity = 0.0
+        case .box:
+            layer.borderColor = theme.text.cgColor
+            layer.borderWidth = 0.5
+            layer.opacity = 0.5
+        }
+
+        layer.frame = rectToHighlight
+
+        // Insert above selection but below text
+        textView.layer?.insertSublayer(layer, at: 1)
+
+        if bracePairHighlight == .flash {
+            addFlashAnimation(to: layer, rectToHighlight: rectToHighlight)
+        }
+
+        highlightLayers.append(layer)
+
+        // Scroll the last rect into view, makes a small assumption that the last rect is the lowest visually.
+        if scrollToRange {
+            textView.scrollToVisible(rectToHighlight)
+        }
+    }
+
+    /// Adds a flash animation to the given layer.
+    /// - Parameters:
+    ///   - layer: The layer to add the animation to.
+    ///   - rectToHighlight: The layer's bounding rect to animate.
+    private func addFlashAnimation(to layer: CALayer, rectToHighlight: CGRect) {
+        CATransaction.begin()
+        CATransaction.setCompletionBlock { [weak self] in
+            if let index = self?.highlightLayers.firstIndex(of: layer) {
+                self?.highlightLayers.remove(at: index)
+            }
+            layer.removeFromSuperlayer()
+        }
+        let duration = 0.75
+        let group = CAAnimationGroup()
+        group.duration = duration
+
+        let opacityAnim = CAKeyframeAnimation(keyPath: "opacity")
+        opacityAnim.duration = duration
+        opacityAnim.values = [1.0, 1.0, 0.0]
+        opacityAnim.keyTimes = [0.1, 0.8, 0.9]
+
+        let positionAnim = CAKeyframeAnimation(keyPath: "position")
+        positionAnim.keyTimes = [0.0, 0.05, 0.1]
+        positionAnim.values = [
+            NSPoint(x: rectToHighlight.origin.x, y: rectToHighlight.origin.y),
+            NSPoint(x: rectToHighlight.origin.x - 2, y: rectToHighlight.origin.y - 2),
+            NSPoint(x: rectToHighlight.origin.x, y: rectToHighlight.origin.y)
+        ]
+        positionAnim.duration = duration
+
+        var betweenSize = rectToHighlight
+        betweenSize.size.width += 4
+        betweenSize.size.height += 4
+        let boundsAnim = CAKeyframeAnimation(keyPath: "bounds")
+        boundsAnim.keyTimes = [0.0, 0.05, 0.1]
+        boundsAnim.values = [rectToHighlight, betweenSize, rectToHighlight]
+        boundsAnim.duration = duration
+
+        group.animations = [opacityAnim, boundsAnim]
+        layer.add(group, forKey: nil)
+        CATransaction.commit()
+    }
+
+    /// Adds a temporary highlight effect to the given range.
+    /// - Parameters:
+    ///   - range: The range to highlight
+    ///   - scrollToRange: Set to true to scroll to the given range when highlighting. Defaults to `false`.
+    public func highlightRange(_ range: NSRange, scrollToRange: Bool = false) {
+        guard let textRange = NSTextRange(range, provider: textView.textContentManager) else {
+            return
+        }
+
+        highlightRange(textRange, scrollToRange: scrollToRange)
+    }
+
+    /// Safely removes all highlight layers.
+    internal func removeHighlightLayers() {
+        highlightLayers.forEach { layer in
+            layer.removeFromSuperlayer()
+        }
+        highlightLayers.removeAll()
+    }
+}
diff --git a/Sources/CodeEditTextView/Controller/STTextViewController+Lifecycle.swift b/Sources/CodeEditTextView/Controller/STTextViewController+Lifecycle.swift
new file mode 100644
index 000000000..4df7397d9
--- /dev/null
+++ b/Sources/CodeEditTextView/Controller/STTextViewController+Lifecycle.swift
@@ -0,0 +1,144 @@
+//
+//  STTextViewController+Lifecycle.swift
+//  CodeEditTextView
+//
+//  Created by Khan Winter on 5/3/23.
+//
+
+import AppKit
+import STTextView
+
+extension STTextViewController {
+    // swiftlint:disable:next function_body_length
+    public override func loadView() {
+        textView = STTextView()
+
+        let scrollView = CEScrollView()
+        scrollView.translatesAutoresizingMaskIntoConstraints = false
+        scrollView.hasVerticalScroller = true
+        scrollView.documentView = textView
+        scrollView.drawsBackground = useThemeBackground
+        scrollView.automaticallyAdjustsContentInsets = contentInsets == nil
+        if let contentInsets = contentInsets {
+            scrollView.contentInsets = contentInsets
+        }
+
+        rulerView = STLineNumberRulerView(textView: textView, scrollView: scrollView)
+        rulerView.backgroundColor = useThemeBackground ? theme.background : .clear
+        rulerView.textColor = .secondaryLabelColor
+        rulerView.drawSeparator = false
+        rulerView.baselineOffset = baselineOffset
+        rulerView.font = rulerFont
+        rulerView.selectedLineHighlightColor = useThemeBackground ? theme.lineHighlight : systemAppearance == .darkAqua
+        ? NSColor.quaternaryLabelColor
+        : NSColor.selectedTextBackgroundColor.withSystemEffect(.disabled)
+        rulerView.rulerInsets = STRulerInsets(leading: rulerFont.pointSize * 1.6, trailing: 8)
+        rulerView.allowsMarkers = false
+
+        if self.isEditable == false {
+            rulerView.selectedLineTextColor = nil
+            rulerView.selectedLineHighlightColor = theme.background
+        }
+
+        scrollView.verticalRulerView = rulerView
+        scrollView.rulersVisible = true
+
+        textView.typingAttributes = attributesFor(nil)
+        textView.defaultParagraphStyle = self.paragraphStyle
+        textView.font = self.font
+        textView.textColor = theme.text
+        textView.backgroundColor = useThemeBackground ? theme.background : .clear
+        textView.insertionPointColor = theme.insertionPoint
+        textView.insertionPointWidth = 1.0
+        textView.selectionBackgroundColor = theme.selection
+        textView.selectedLineHighlightColor = useThemeBackground ? theme.lineHighlight : systemAppearance == .darkAqua
+        ? NSColor.quaternaryLabelColor
+        : NSColor.selectedTextBackgroundColor.withSystemEffect(.disabled)
+        textView.string = self.text.wrappedValue
+        textView.isEditable = self.isEditable
+        textView.highlightSelectedLine = true
+        textView.allowsUndo = true
+        textView.setupMenus()
+        textView.delegate = self
+        textView.highlightSelectedLine = self.isEditable
+
+        scrollView.documentView = textView
+
+        scrollView.translatesAutoresizingMaskIntoConstraints = false
+
+        self.view = scrollView
+
+        NSLayoutConstraint.activate([
+            scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
+            scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
+            scrollView.topAnchor.constraint(equalTo: view.topAnchor),
+            scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
+        ])
+
+        NSEvent.addLocalMonitorForEvents(matching: .keyDown) { event in
+            self.keyDown(with: event)
+            return event
+        }
+
+        setUpHighlighter()
+        setHighlightProvider(self.highlightProvider)
+        setUpTextFormation()
+
+        self.setCursorPosition(self.cursorPosition.wrappedValue)
+    }
+
+    public override func viewDidLoad() {
+        super.viewDidLoad()
+
+        NotificationCenter.default.addObserver(forName: NSWindow.didResizeNotification,
+                                               object: nil,
+                                               queue: .main) { [weak self] _ in
+            guard let self = self else { return }
+            (self.view as? NSScrollView)?.contentView.contentInsets.bottom = self.bottomContentInsets
+            self.updateTextContainerWidthIfNeeded()
+        }
+
+        NotificationCenter.default.addObserver(
+            forName: STTextView.didChangeSelectionNotification,
+            object: nil,
+            queue: .main
+        ) { [weak self] _ in
+            let textSelections = self?.textView.textLayoutManager.textSelections.flatMap(\.textRanges)
+            guard self?.lastTextSelections != textSelections else {
+                return
+            }
+            self?.lastTextSelections = textSelections ?? []
+
+            self?.removeHighlightLayers()
+            self?.updateCursorPosition()
+            self?.highlightSelectionPairs()
+        }
+
+        NotificationCenter.default.addObserver(
+            forName: NSView.frameDidChangeNotification,
+            object: (self.view as? NSScrollView)?.verticalRulerView,
+            queue: .main
+        ) { [weak self] _ in
+            self?.removeHighlightLayers()
+            self?.updateTextContainerWidthIfNeeded()
+        }
+
+        systemAppearance = NSApp.effectiveAppearance.name
+
+        NSApp.publisher(for: \.effectiveAppearance)
+            .receive(on: RunLoop.main)
+            .sink { [weak self] newValue in
+                guard let self = self else { return }
+
+                if self.systemAppearance != newValue.name {
+                    self.systemAppearance = newValue.name
+                }
+            }
+            .store(in: &cancellables)
+    }
+
+    public override func viewWillAppear() {
+        super.viewWillAppear()
+        updateTextContainerWidthIfNeeded()
+    }
+}
diff --git a/Sources/CodeEditTextView/Controller/STTextViewController.swift b/Sources/CodeEditTextView/Controller/STTextViewController.swift
index f5543a82d..4570b327b 100644
--- a/Sources/CodeEditTextView/Controller/STTextViewController.swift
+++ b/Sources/CodeEditTextView/Controller/STTextViewController.swift
@@ -19,6 +19,13 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
 
     internal var rulerView: STLineNumberRulerView!
 
+    /// Internal reference to any injected layers in the text view.
+    internal var highlightLayers: [CALayer] = []
+
+    /// Tracks the last text selections. Used to debounce `STTextView.didChangeSelectionNotification` being sent twice
+    /// for every new selection.
+    internal var lastTextSelections: [NSTextRange] = []
+
     /// Binding for the `textView`s string
     public var text: Binding<String>
 
@@ -88,6 +95,15 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
         }
     }
 
+    /// The type of highlight to use when highlighting brace pairs. Leave as `nil` to disable highlighting.
+    public var bracePairHighlight: BracePairHighlight? {
+        didSet {
+            removeHighlightLayers()
+            // Update selection highlights if needed.
+            highlightSelectionPairs()
+        }
+    }
+
     /// The kern to use for characters. Defaults to `0.0` and is updated when `letterSpacing` is set.
     internal var kern: CGFloat = 0.0
 
@@ -119,7 +135,8 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
         highlightProvider: HighlightProviding? = nil,
         contentInsets: NSEdgeInsets? = nil,
         isEditable: Bool,
-        letterSpacing: Double
+        letterSpacing: Double,
+        bracePairHighlight: BracePairHighlight? = nil
     ) {
         self.text = text
         self.language = language
@@ -135,6 +152,7 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
         self.highlightProvider = highlightProvider
         self.contentInsets = contentInsets
         self.isEditable = isEditable
+        self.bracePairHighlight = bracePairHighlight
         super.init(nibName: nil, bundle: nil)
     }
 
@@ -142,132 +160,6 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
         fatalError()
     }
 
-    // MARK: VC Lifecycle
-
-    // swiftlint:disable:next function_body_length
-    public override func loadView() {
-        textView = STTextView()
-
-        let scrollView = CEScrollView()
-        scrollView.translatesAutoresizingMaskIntoConstraints = false
-        scrollView.hasVerticalScroller = true
-        scrollView.documentView = textView
-        scrollView.drawsBackground = useThemeBackground
-        scrollView.automaticallyAdjustsContentInsets = contentInsets == nil
-        if let contentInsets = contentInsets {
-            scrollView.contentInsets = contentInsets
-        }
-
-        rulerView = STLineNumberRulerView(textView: textView, scrollView: scrollView)
-        rulerView.backgroundColor = useThemeBackground ? theme.background : .clear
-        rulerView.textColor = .secondaryLabelColor
-        rulerView.drawSeparator = false
-        rulerView.baselineOffset = baselineOffset
-        rulerView.font = rulerFont
-        rulerView.selectedLineHighlightColor = useThemeBackground ? theme.lineHighlight : systemAppearance == .darkAqua
-            ? NSColor.quaternaryLabelColor
-            : NSColor.selectedTextBackgroundColor.withSystemEffect(.disabled)
-        rulerView.rulerInsets = STRulerInsets(leading: rulerFont.pointSize * 1.6, trailing: 8)
-        rulerView.allowsMarkers = false
-
-        if self.isEditable == false {
-            rulerView.selectedLineTextColor = nil
-            rulerView.selectedLineHighlightColor = theme.background
-        }
-
-        scrollView.verticalRulerView = rulerView
-        scrollView.rulersVisible = true
-
-        textView.typingAttributes = attributesFor(nil)
-        textView.defaultParagraphStyle = self.paragraphStyle
-        textView.font = self.font
-        textView.textColor = theme.text
-        textView.backgroundColor = useThemeBackground ? theme.background : .clear
-        textView.insertionPointColor = theme.insertionPoint
-        textView.insertionPointWidth = 1.0
-        textView.selectionBackgroundColor = theme.selection
-        textView.selectedLineHighlightColor = useThemeBackground ? theme.lineHighlight : systemAppearance == .darkAqua
-            ? NSColor.quaternaryLabelColor
-            : NSColor.selectedTextBackgroundColor.withSystemEffect(.disabled)
-        textView.string = self.text.wrappedValue
-        textView.isEditable = self.isEditable
-        textView.highlightSelectedLine = true
-        textView.allowsUndo = true
-        textView.setupMenus()
-        textView.delegate = self
-        textView.highlightSelectedLine = self.isEditable
-
-        scrollView.documentView = textView
-
-        scrollView.translatesAutoresizingMaskIntoConstraints = false
-
-        self.view = scrollView
-
-        NSLayoutConstraint.activate([
-            scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
-            scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
-            scrollView.topAnchor.constraint(equalTo: view.topAnchor),
-            scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
-        ])
-
-        NSEvent.addLocalMonitorForEvents(matching: .keyDown) { event in
-            self.keyDown(with: event)
-            return event
-        }
-
-        setUpHighlighter()
-        setHighlightProvider(self.highlightProvider)
-        setUpTextFormation()
-
-        self.setCursorPosition(self.cursorPosition.wrappedValue)
-    }
-
-    public override func viewDidLoad() {
-        super.viewDidLoad()
-
-        NotificationCenter.default.addObserver(forName: NSWindow.didResizeNotification,
-                                               object: nil,
-                                               queue: .main) { [weak self] _ in
-            guard let self = self else { return }
-            (self.view as? NSScrollView)?.contentView.contentInsets.bottom = self.bottomContentInsets
-            self.updateTextContainerWidthIfNeeded()
-        }
-
-        NotificationCenter.default.addObserver(
-            forName: STTextView.didChangeSelectionNotification,
-            object: nil,
-            queue: .main
-        ) { [weak self] _ in
-            self?.updateCursorPosition()
-        }
-
-        NotificationCenter.default.addObserver(
-            forName: NSView.frameDidChangeNotification,
-            object: (self.view as? NSScrollView)?.verticalRulerView,
-            queue: .main
-        ) { [weak self] _ in
-            self?.updateTextContainerWidthIfNeeded()
-        }
-
-        systemAppearance = NSApp.effectiveAppearance.name
-
-        NSApp.publisher(for: \.effectiveAppearance)
-            .receive(on: RunLoop.main)
-            .sink { [weak self] newValue in
-                guard let self = self else { return }
-
-                if self.systemAppearance != newValue.name {
-                    self.systemAppearance = newValue.name
-                }
-            }
-            .store(in: &cancellables)
-    }
-
-    public override func viewWillAppear() {
-        super.viewWillAppear()
-        updateTextContainerWidthIfNeeded()
-    }
-
     public func textViewDidChangeText(_ notification: Notification) {
         self.text.wrappedValue = textView.string
     }
@@ -288,7 +180,7 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
     }
 
     /// ScrollView's bottom inset using as editor overscroll
-    private var bottomContentInsets: CGFloat {
+    internal var bottomContentInsets: CGFloat {
         let height = view.frame.height
         var inset = editorOverscroll * height
 
@@ -350,7 +242,9 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
     // MARK: Selectors
 
     override public func keyDown(with event: NSEvent) {
-        // This should be uneccessary but if removed STTextView receives some `keydown`s twice.
+        if !highlightLayers.isEmpty {
+            removeHighlightLayers()
+        }
     }
 
     public override func insertTab(_ sender: Any?) {
@@ -358,6 +252,7 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
     }
 
     deinit {
+        removeHighlightLayers()
         textView = nil
         highlighter = nil
         cancellables.forEach { $0.cancel() }
diff --git a/Sources/CodeEditTextView/Enums/BracePairHighlight.swift b/Sources/CodeEditTextView/Enums/BracePairHighlight.swift
new file mode 100644
index 000000000..9574d4e4b
--- /dev/null
+++ b/Sources/CodeEditTextView/Enums/BracePairHighlight.swift
@@ -0,0 +1,18 @@
+//
+//  BracePairHighlight.swift
+//  CodeEditTextView
+//
+//  Created by Khan Winter on 5/3/23.
+//
+
+/// An enum representing the type of highlight to use for brace pairs.
+public enum BracePairHighlight {
+    /// Highlight both the opening and closing character in a pair with a bounding box.
+    /// The box will use the theme's text color with some opacity. The boxes will stay on screen until the cursor moves
+    /// away from the brace pair.
+    case box
+    /// Flash a yellow highlight box on only the opposite character in the pair.
+    /// This is closely matched to Xcode's flash highlight for brace pairs, and animates in and out over the course
+    /// of `0.75` seconds.
+    case flash
+}
diff --git a/Sources/CodeEditTextView/Filters/STTextViewController+TextFormation.swift b/Sources/CodeEditTextView/Filters/STTextViewController+TextFormation.swift
index 202e00181..c62fb79c5 100644
--- a/Sources/CodeEditTextView/Filters/STTextViewController+TextFormation.swift
+++ b/Sources/CodeEditTextView/Filters/STTextViewController+TextFormation.swift
@@ -12,6 +12,15 @@ import TextStory
 
 extension STTextViewController {
 
+    internal enum BracePairs {
+        static let allValues: [(String, String)] = [
+            ("{", "}"),
+            ("[", "]"),
+            ("(", ")"),
+            ("<", ">")
+        ]
+    }
+
     // MARK: - Filter Configuration
 
     /// Initializes any filters for text editing.
@@ -20,13 +29,6 @@ extension STTextViewController {
 
         let indentationUnit = indentOption.stringValue
 
-        let pairsToHandle: [(String, String)] = [
-            ("{", "}"),
-            ("[", "]"),
-            ("(", ")"),
-            ("<", ">")
-        ]
-
         let indenter: TextualIndenter = getTextIndenter()
         let whitespaceProvider = WhitespaceProviders(
             leadingWhitespace: indenter.substitionProvider(indentationUnit: indentationUnit,
@@ -36,10 +38,10 @@ extension STTextViewController {
 
         // Filters
 
-        setUpOpenPairFilters(pairs: pairsToHandle, whitespaceProvider: whitespaceProvider)
+        setUpOpenPairFilters(pairs: BracePairs.allValues, whitespaceProvider: whitespaceProvider)
         setUpNewlineTabFilters(whitespaceProvider: whitespaceProvider,
                                indentOption: indentOption)
-        setUpDeletePairFilters(pairs: pairsToHandle)
+        setUpDeletePairFilters(pairs: BracePairs.allValues)
         setUpDeleteWhitespaceFilter(indentOption: indentOption)
     }
 
diff --git a/Sources/CodeEditTextView/TreeSitter/TreeSitterClient+Edit.swift b/Sources/CodeEditTextView/TreeSitter/TreeSitterClient+Edit.swift
index b7a31329e..871d59cf6 100644
--- a/Sources/CodeEditTextView/TreeSitter/TreeSitterClient+Edit.swift
+++ b/Sources/CodeEditTextView/TreeSitter/TreeSitterClient+Edit.swift
@@ -79,10 +79,10 @@ extension TreeSitterClient {
     /// - Returns: Any changed ranges.
     internal func changedByteRanges(_ lhs: Tree?, rhs: Tree?) -> [Range<UInt32>] {
         switch (lhs, rhs) {
-        case (let t1?, let t2?):
-            return t1.changedRanges(from: t2).map({ $0.bytes })
-        case (nil, let t2?):
-            let range = t2.rootNode?.byteRange
+        case (let tree1?, let tree2?):
+            return tree1.changedRanges(from: tree2).map({ $0.bytes })
+        case (nil, let tree2?):
+            let range = tree2.rootNode?.byteRange
 
             return range.flatMap({ [$0] }) ?? []
         case (_, nil):
diff --git a/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift b/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift
index 1f9914238..cb5a6528b 100644
--- a/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift
+++ b/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift
@@ -215,5 +215,68 @@ final class STTextViewControllerTests: XCTestCase {
 
         controller.letterSpacing = 1.0
     }
+
+    func test_braceHighlights() {
+        controller.viewDidLoad()
+        controller.bracePairHighlight = nil
+        controller.textView.string = "{ Loren Ipsum {} }"
+        controller.setCursorPosition((1, 2)) // After first opening {
+        XCTAssert(controller.highlightLayers.isEmpty, "Controller added highlight layer when setting is set to `nil`")
+
+        controller.bracePairHighlight = .box
+        controller.setCursorPosition((1, 2)) // After first opening {
+        XCTAssert(controller.highlightLayers.count == 2, "Controller created an incorrect number of layers for the box. Expected 2, found \(controller.highlightLayers.count)")
+        controller.setCursorPosition((1, 3))
+        XCTAssert(controller.highlightLayers.isEmpty, "Controller failed to remove brace pair layers.")
+
+        controller.bracePairHighlight = .flash
+        controller.setCursorPosition((1, 2)) // After first opening {
+        XCTAssert(controller.highlightLayers.count == 1, "Controller created more than one layer for flash animation. Expected 1, found \(controller.highlightLayers.count)")
+        controller.setCursorPosition((1, 3))
+        XCTAssert(controller.highlightLayers.isEmpty, "Controller failed to remove brace pair layers.")
+
+        controller.setCursorPosition((1, 2)) // After first opening {
+        XCTAssert(controller.highlightLayers.count == 1, "Controller created more than one layer for flash animation. Expected 1, found \(controller.highlightLayers.count)")
+        let exp = expectation(description: "Test after 0.8 seconds")
+        let result = XCTWaiter.wait(for: [exp], timeout: 0.8)
+        if result == XCTWaiter.Result.timedOut {
+            XCTAssert(controller.highlightLayers.isEmpty, "Controller failed to remove layer after flash animation. Expected 0, found \(controller.highlightLayers.count)")
+        } else {
+            XCTFail("Delay interrupted")
+        }
+    }
+
+    func test_findClosingPair() {
+        controller.textView.string = "{ Loren Ipsum {} }"
+        var idx: Int?
+
+        // Test walking forwards
+        idx = controller.findClosingPair("{", "}", from: 1, limit: 18, reverse: false)
+        XCTAssert(idx == 17, "Walking forwards failed. Expected `17`, found: `\(String(describing: idx))`")
+
+        // Test walking backwards
+        idx = controller.findClosingPair("}", "{", from: 17, limit: 0, reverse: true)
+        XCTAssert(idx == 0, "Walking backwards failed. Expected `0`, found: `\(String(describing: idx))`")
+
+        // Test extra pair
+        controller.textView.string = "{ Loren Ipsum {}} }"
+        idx = controller.findClosingPair("{", "}", from: 1, limit: 19, reverse: false)
+        XCTAssert(idx == 16, "Walking forwards with extra brace pair failed. Expected `16`, found: `\(String(describing: idx))`")
+
+        // Text extra pair backwards
+        controller.textView.string = "{ Loren Ipsum {{} }"
+        idx = controller.findClosingPair("}", "{", from: 18, limit: 0, reverse: true)
+        XCTAssert(idx == 14, "Walking backwards with extra brace pair failed. Expected `14`, found: `\(String(describing: idx))`")
+
+        // Test missing pair
+        controller.textView.string = "{ Loren Ipsum { }"
+        idx = controller.findClosingPair("{", "}", from: 1, limit: 17, reverse: false)
+        XCTAssert(idx == nil, "Walking forwards with missing pair failed. Expected `nil`, found: `\(String(describing: idx))`")
+
+        // Test missing pair backwards
+        controller.textView.string = " Loren Ipsum {} }"
+        idx = controller.findClosingPair("}", "{", from: 17, limit: 0, reverse: true)
+        XCTAssert(idx == nil, "Walking backwards with missing pair failed. Expected `nil`, found: `\(String(describing: idx))`")
+    }
 }
 // swiftlint:enable all

From f675fbc817335bcd1f2fa69b8d427ee544a0f3e7 Mon Sep 17 00:00:00 2001
From: Khan Winter <35942988+thecoolwinter@users.noreply.github.com>
Date: Wed, 3 May 2023 16:38:02 -0500
Subject: [PATCH 2/7] Make `highlightRange(...)` private

---
 .../Controller/STTextViewController+HighlightRange.swift        | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift b/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift
index 7ac49de1c..db4485251 100644
--- a/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift
+++ b/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift
@@ -106,7 +106,7 @@ extension STTextViewController {
     /// - Parameters:
     ///   - range: The range to highlight
     ///   - scrollToRange: Set to true to scroll to the given range when highlighting. Defaults to `false`.
-    public func highlightRange(_ range: NSTextRange, scrollToRange: Bool = false) {
+    private func highlightRange(_ range: NSTextRange, scrollToRange: Bool = false) {
         guard let bracePairHighlight = bracePairHighlight,
               var rectToHighlight = textView.textLayoutManager.textSelectionSegmentFrame(
                 in: range, type: .highlight

From 8a27dd8a51581cafd6476e572ed77c0e3d0f623a Mon Sep 17 00:00:00 2001
From: Khan Winter <35942988+thecoolwinter@users.noreply.github.com>
Date: Wed, 3 May 2023 16:50:45 -0500
Subject: [PATCH 3/7] Pin `STTextView`

---
 Package.swift | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Package.swift b/Package.swift
index 6fd9c8ac5..244bfd4ad 100644
--- a/Package.swift
+++ b/Package.swift
@@ -15,7 +15,7 @@ let package = Package(
     dependencies: [
         .package(
             url: "https://github.com/krzyzanowskim/STTextView.git",
-            from: "0.5.3"
+            exact: "0.5.3"
         ),
         .package(
             url: "https://github.com/CodeEditApp/CodeEditLanguages.git",

From f8b4b268ee36d2b08ec39176cb9008cadb2a0516 Mon Sep 17 00:00:00 2001
From: Khan Winter <35942988+thecoolwinter@users.noreply.github.com>
Date: Sun, 7 May 2023 20:13:21 -0500
Subject: [PATCH 4/7] Rename to `bracket`, add `.underline(color:)`

---
 .../CodeEditTextView/CodeEditTextView.swift   | 16 +++----
 .../STTextViewController+HighlightRange.swift | 38 +++++++++++-----
 .../Controller/STTextViewController.swift     |  8 ++--
 .../Enums/BracePairHighlight.swift            | 18 --------
 .../Enums/BracketPairHighlight.swift          | 45 +++++++++++++++++++
 .../STTextViewController+TextFormation.swift  |  6 +--
 .../STTextViewControllerTests.swift           | 16 +++----
 7 files changed, 94 insertions(+), 53 deletions(-)
 delete mode 100644 Sources/CodeEditTextView/Enums/BracePairHighlight.swift
 create mode 100644 Sources/CodeEditTextView/Enums/BracketPairHighlight.swift

diff --git a/Sources/CodeEditTextView/CodeEditTextView.swift b/Sources/CodeEditTextView/CodeEditTextView.swift
index c340f42ce..a0ac4390e 100644
--- a/Sources/CodeEditTextView/CodeEditTextView.swift
+++ b/Sources/CodeEditTextView/CodeEditTextView.swift
@@ -33,8 +33,8 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
     ///   - isEditable: A Boolean value that controls whether the text view allows the user to edit text.
     ///   - letterSpacing: The amount of space to use between letters, as a percent. Eg: `1.0` = no space, `1.5` = 1/2 a
     ///                    character's width between characters, etc. Defaults to `1.0`
-    ///   - bracePairHighlight: The type of highlight to use to highlight brace pairs.
-    ///                         See `BracePairHighlight` for more information.
+    ///   - bracketPairHighlight: The type of highlight to use to highlight bracket pairs.
+    ///                           See `BracketPairHighlight` for more information. Defaults to `nil`
     public init(
         _ text: Binding<String>,
         language: CodeLanguage,
@@ -51,7 +51,7 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
         contentInsets: NSEdgeInsets? = nil,
         isEditable: Bool = true,
         letterSpacing: Double = 1.0,
-        bracePairHighlight: BracePairHighlight? = nil
+        bracketPairHighlight: BracketPairHighlight? = nil
     ) {
         self._text = text
         self.language = language
@@ -68,7 +68,7 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
         self.contentInsets = contentInsets
         self.isEditable = isEditable
         self.letterSpacing = letterSpacing
-        self.bracePairHighlight = bracePairHighlight
+        self.bracketPairHighlight = bracketPairHighlight
     }
 
     @Binding private var text: String
@@ -86,7 +86,7 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
     private var contentInsets: NSEdgeInsets?
     private var isEditable: Bool
     private var letterSpacing: Double
-    private var bracePairHighlight: BracePairHighlight?
+    private var bracketPairHighlight: BracketPairHighlight?
 
     public typealias NSViewControllerType = STTextViewController
 
@@ -107,7 +107,7 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
             contentInsets: contentInsets,
             isEditable: isEditable,
             letterSpacing: letterSpacing,
-            bracePairHighlight: bracePairHighlight
+            bracketPairHighlight: bracketPairHighlight
         )
         return controller
     }
@@ -125,7 +125,7 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
         controller.lineHeightMultiple = lineHeight
         controller.editorOverscroll = editorOverscroll
         controller.contentInsets = contentInsets
-        controller.bracePairHighlight = bracePairHighlight
+        controller.bracketPairHighlight = bracketPairHighlight
 
         // Updating the language, theme, tab width and indent option needlessly can cause highlights to be re-calculated
         if controller.language.id != language.id {
@@ -160,6 +160,6 @@ public struct CodeEditTextView: NSViewControllerRepresentable {
         controller.indentOption == indentOption &&
         controller.tabWidth == tabWidth &&
         controller.letterSpacing == letterSpacing &&
-        controller.bracePairHighlight == bracePairHighlight
+        controller.bracketPairHighlight == bracketPairHighlight
     }
 }
diff --git a/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift b/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift
index db4485251..f71e05ed3 100644
--- a/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift
+++ b/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift
@@ -9,9 +9,9 @@ import AppKit
 import STTextView
 
 extension STTextViewController {
-    /// Highlights brace pairs using the current selection.
+    /// Highlights bracket pairs using the current selection.
     internal func highlightSelectionPairs() {
-        guard bracePairHighlight != nil else { return }
+        guard bracketPairHighlight != nil else { return }
         for selection in textView.textLayoutManager.textSelections.flatMap(\.textRanges) {
             if selection.isEmpty,
                let range = selection.nsRange(using: textView.textContentManager),
@@ -19,7 +19,7 @@ extension STTextViewController {
                let preceedingCharacter = textView.textContentStorage?.textStorage?.substring(
                 from: NSRange(location: range.location - 1, length: 1) // The preceeding character exists
                ) {
-                for pair in BracePairs.allValues {
+                for pair in BracketPairs.allValues {
                     if preceedingCharacter == pair.0 {
                         // Walk forwards
                         if let characterIndex = findClosingPair(
@@ -31,7 +31,7 @@ extension STTextViewController {
                             reverse: false
                         ) {
                             highlightRange(NSRange(location: characterIndex, length: 1))
-                            if bracePairHighlight == .box {
+                            if bracketPairHighlight?.highlightsSourceBracket ?? false {
                                 highlightRange(NSRange(location: range.location - 1, length: 1))
                             }
                         }
@@ -46,7 +46,7 @@ extension STTextViewController {
                             reverse: true
                         ) {
                             highlightRange(NSRange(location: characterIndex, length: 1))
-                            if bracePairHighlight == .box {
+                            if bracketPairHighlight?.highlightsSourceBracket ?? false {
                                 highlightRange(NSRange(location: range.location - 1, length: 1))
                             }
                         }
@@ -107,7 +107,7 @@ extension STTextViewController {
     ///   - range: The range to highlight
     ///   - scrollToRange: Set to true to scroll to the given range when highlighting. Defaults to `false`.
     private func highlightRange(_ range: NSTextRange, scrollToRange: Bool = false) {
-        guard let bracePairHighlight = bracePairHighlight,
+        guard let bracketPairHighlight = bracketPairHighlight,
               var rectToHighlight = textView.textLayoutManager.textSelectionSegmentFrame(
                 in: range, type: .highlight
         ) else {
@@ -115,7 +115,7 @@ extension STTextViewController {
         }
         let layer = CAShapeLayer()
 
-        switch bracePairHighlight {
+        switch bracketPairHighlight {
         case .flash:
             rectToHighlight.size.width += 4
             rectToHighlight.origin.x -= 2
@@ -127,18 +127,32 @@ extension STTextViewController {
             layer.shadowOffset = CGSize(width: 0, height: 1)
             layer.shadowRadius = 3.0
             layer.opacity = 0.0
-        case .box:
-            layer.borderColor = theme.text.cgColor
+        case .bordered(let borderColor):
+            layer.borderColor = borderColor.cgColor
+            layer.cornerRadius = 2.5
             layer.borderWidth = 0.5
-            layer.opacity = 0.5
+            layer.opacity = 1.0
+        case .underline(let underlineColor):
+            layer.lineWidth = 1.0
+            layer.lineCap = .round
+            layer.strokeColor = underlineColor.cgColor
+            layer.opacity = 1.0
         }
 
-        layer.frame = rectToHighlight
+        switch bracketPairHighlight {
+        case .flash, .bordered:
+            layer.frame = rectToHighlight
+        case .underline:
+            let path = CGMutablePath()
+            path.move(to: CGPoint(x: rectToHighlight.minX, y: rectToHighlight.maxY))
+            path.addLine(to: CGPoint(x: rectToHighlight.maxX, y: rectToHighlight.maxY))
+            layer.path = path
+        }
 
         // Insert above selection but below text
         textView.layer?.insertSublayer(layer, at: 1)
 
-        if bracePairHighlight == .flash {
+        if bracketPairHighlight == .flash {
             addFlashAnimation(to: layer, rectToHighlight: rectToHighlight)
         }
 
diff --git a/Sources/CodeEditTextView/Controller/STTextViewController.swift b/Sources/CodeEditTextView/Controller/STTextViewController.swift
index 4570b327b..4785c6267 100644
--- a/Sources/CodeEditTextView/Controller/STTextViewController.swift
+++ b/Sources/CodeEditTextView/Controller/STTextViewController.swift
@@ -95,8 +95,8 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
         }
     }
 
-    /// The type of highlight to use when highlighting brace pairs. Leave as `nil` to disable highlighting.
-    public var bracePairHighlight: BracePairHighlight? {
+    /// The type of highlight to use when highlighting bracket pairs. Leave as `nil` to disable highlighting.
+    public var bracketPairHighlight: BracketPairHighlight? {
         didSet {
             removeHighlightLayers()
             // Update selection highlights if needed.
@@ -136,7 +136,7 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
         contentInsets: NSEdgeInsets? = nil,
         isEditable: Bool,
         letterSpacing: Double,
-        bracePairHighlight: BracePairHighlight? = nil
+        bracketPairHighlight: BracketPairHighlight? = nil
     ) {
         self.text = text
         self.language = language
@@ -152,7 +152,7 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
         self.highlightProvider = highlightProvider
         self.contentInsets = contentInsets
         self.isEditable = isEditable
-        self.bracePairHighlight = bracePairHighlight
+        self.bracketPairHighlight = bracketPairHighlight
         super.init(nibName: nil, bundle: nil)
     }
 
diff --git a/Sources/CodeEditTextView/Enums/BracePairHighlight.swift b/Sources/CodeEditTextView/Enums/BracePairHighlight.swift
deleted file mode 100644
index 9574d4e4b..000000000
--- a/Sources/CodeEditTextView/Enums/BracePairHighlight.swift
+++ /dev/null
@@ -1,18 +0,0 @@
-//
-//  BracePairHighlight.swift
-//  CodeEditTextView
-//
-//  Created by Khan Winter on 5/3/23.
-//
-
-/// An enum representing the type of highlight to use for brace pairs.
-public enum BracePairHighlight {
-    /// Highlight both the opening and closing character in a pair with a bounding box.
-    /// The box will use the theme's text color with some opacity. The boxes will stay on screen until the cursor moves
-    /// away from the brace pair.
-    case box
-    /// Flash a yellow highlight box on only the opposite character in the pair.
-    /// This is closely matched to Xcode's flash highlight for brace pairs, and animates in and out over the course
-    /// of `0.75` seconds.
-    case flash
-}
diff --git a/Sources/CodeEditTextView/Enums/BracketPairHighlight.swift b/Sources/CodeEditTextView/Enums/BracketPairHighlight.swift
new file mode 100644
index 000000000..026abf539
--- /dev/null
+++ b/Sources/CodeEditTextView/Enums/BracketPairHighlight.swift
@@ -0,0 +1,45 @@
+//
+//  BracketPairHighlight.swift
+//  CodeEditTextView
+//
+//  Created by Khan Winter on 5/3/23.
+//
+
+import AppKit
+
+/// An enum representing the type of highlight to use for bracket pairs.
+public enum BracketPairHighlight: Equatable {
+    /// Highlight both the opening and closing character in a pair with a bounding box.
+    /// The boxes will stay on screen until the cursor moves away from the bracket pair.
+    case bordered(color: NSColor)
+    /// Flash a yellow highlight box on only the opposite character in the pair.
+    /// This is closely matched to Xcode's flash highlight for bracket pairs, and animates in and out over the course
+    /// of `0.75` seconds.
+    case flash
+    /// Highlight both the opening and closing character in a pair with an underline.
+    /// The underline will stay on screen until the cursor moves away from the bracket pair.
+    case underline(color: NSColor)
+
+    public static func == (lhs: BracketPairHighlight, rhs: BracketPairHighlight) -> Bool {
+        switch (lhs, rhs) {
+        case (.flash, .flash):
+            return true
+        case (.bordered(let lhsColor), .bordered(let rhsColor)):
+            return lhsColor == rhsColor
+        case (.underline(let lhsColor), .underline(let rhsColor)):
+            return lhsColor == rhsColor
+        default:
+            return false
+        }
+    }
+
+    /// Returns `true` if the highlight should act on both the opening and closing bracket.
+    var highlightsSourceBracket: Bool {
+        switch self {
+        case .bordered, .underline:
+            return true
+        case .flash:
+            return false
+        }
+    }
+}
diff --git a/Sources/CodeEditTextView/Filters/STTextViewController+TextFormation.swift b/Sources/CodeEditTextView/Filters/STTextViewController+TextFormation.swift
index c62fb79c5..5e24773ed 100644
--- a/Sources/CodeEditTextView/Filters/STTextViewController+TextFormation.swift
+++ b/Sources/CodeEditTextView/Filters/STTextViewController+TextFormation.swift
@@ -12,7 +12,7 @@ import TextStory
 
 extension STTextViewController {
 
-    internal enum BracePairs {
+    internal enum BracketPairs {
         static let allValues: [(String, String)] = [
             ("{", "}"),
             ("[", "]"),
@@ -38,10 +38,10 @@ extension STTextViewController {
 
         // Filters
 
-        setUpOpenPairFilters(pairs: BracePairs.allValues, whitespaceProvider: whitespaceProvider)
+        setUpOpenPairFilters(pairs: BracketPairs.allValues, whitespaceProvider: whitespaceProvider)
         setUpNewlineTabFilters(whitespaceProvider: whitespaceProvider,
                                indentOption: indentOption)
-        setUpDeletePairFilters(pairs: BracePairs.allValues)
+        setUpDeletePairFilters(pairs: BracketPairs.allValues)
         setUpDeleteWhitespaceFilter(indentOption: indentOption)
     }
 
diff --git a/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift b/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift
index cb5a6528b..c3de0ba8e 100644
--- a/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift
+++ b/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift
@@ -216,24 +216,24 @@ final class STTextViewControllerTests: XCTestCase {
         controller.letterSpacing = 1.0
     }
 
-    func test_braceHighlights() {
+    func test_bracketHighlights() {
         controller.viewDidLoad()
-        controller.bracePairHighlight = nil
+        controller.bracketPairHighlight = nil
         controller.textView.string = "{ Loren Ipsum {} }"
         controller.setCursorPosition((1, 2)) // After first opening {
         XCTAssert(controller.highlightLayers.isEmpty, "Controller added highlight layer when setting is set to `nil`")
 
-        controller.bracePairHighlight = .box
+        controller.bracketPairHighlight = .bordered
         controller.setCursorPosition((1, 2)) // After first opening {
         XCTAssert(controller.highlightLayers.count == 2, "Controller created an incorrect number of layers for the box. Expected 2, found \(controller.highlightLayers.count)")
         controller.setCursorPosition((1, 3))
-        XCTAssert(controller.highlightLayers.isEmpty, "Controller failed to remove brace pair layers.")
+        XCTAssert(controller.highlightLayers.isEmpty, "Controller failed to remove bracket pair layers.")
 
-        controller.bracePairHighlight = .flash
+        controller.bracketPairHighlight = .flash
         controller.setCursorPosition((1, 2)) // After first opening {
         XCTAssert(controller.highlightLayers.count == 1, "Controller created more than one layer for flash animation. Expected 1, found \(controller.highlightLayers.count)")
         controller.setCursorPosition((1, 3))
-        XCTAssert(controller.highlightLayers.isEmpty, "Controller failed to remove brace pair layers.")
+        XCTAssert(controller.highlightLayers.isEmpty, "Controller failed to remove bracket pair layers.")
 
         controller.setCursorPosition((1, 2)) // After first opening {
         XCTAssert(controller.highlightLayers.count == 1, "Controller created more than one layer for flash animation. Expected 1, found \(controller.highlightLayers.count)")
@@ -261,12 +261,12 @@ final class STTextViewControllerTests: XCTestCase {
         // Test extra pair
         controller.textView.string = "{ Loren Ipsum {}} }"
         idx = controller.findClosingPair("{", "}", from: 1, limit: 19, reverse: false)
-        XCTAssert(idx == 16, "Walking forwards with extra brace pair failed. Expected `16`, found: `\(String(describing: idx))`")
+        XCTAssert(idx == 16, "Walking forwards with extra bracket pair failed. Expected `16`, found: `\(String(describing: idx))`")
 
         // Text extra pair backwards
         controller.textView.string = "{ Loren Ipsum {{} }"
         idx = controller.findClosingPair("}", "{", from: 18, limit: 0, reverse: true)
-        XCTAssert(idx == 14, "Walking backwards with extra brace pair failed. Expected `14`, found: `\(String(describing: idx))`")
+        XCTAssert(idx == 14, "Walking backwards with extra bracket pair failed. Expected `14`, found: `\(String(describing: idx))`")
 
         // Test missing pair
         controller.textView.string = "{ Loren Ipsum { }"

From 79098f03eb6d474338fda3050ca8753d1934be20 Mon Sep 17 00:00:00 2001
From: Khan Winter <35942988+thecoolwinter@users.noreply.github.com>
Date: Sun, 7 May 2023 20:17:03 -0500
Subject: [PATCH 5/7] Add `underline(color:)` test

---
 .../STTextViewControllerTests.swift                    | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift b/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift
index c3de0ba8e..9fd465b27 100644
--- a/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift
+++ b/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift
@@ -223,9 +223,15 @@ final class STTextViewControllerTests: XCTestCase {
         controller.setCursorPosition((1, 2)) // After first opening {
         XCTAssert(controller.highlightLayers.isEmpty, "Controller added highlight layer when setting is set to `nil`")
 
-        controller.bracketPairHighlight = .bordered
+        controller.bracketPairHighlight = .bordered(color: .black)
         controller.setCursorPosition((1, 2)) // After first opening {
-        XCTAssert(controller.highlightLayers.count == 2, "Controller created an incorrect number of layers for the box. Expected 2, found \(controller.highlightLayers.count)")
+        XCTAssert(controller.highlightLayers.count == 2, "Controller created an incorrect number of layers for bordered. Expected 2, found \(controller.highlightLayers.count)")
+        controller.setCursorPosition((1, 3))
+        XCTAssert(controller.highlightLayers.isEmpty, "Controller failed to remove bracket pair layers.")
+
+        controller.bracketPairHighlight = .underline(color: .black)
+        controller.setCursorPosition((1, 2)) // After first opening {
+        XCTAssert(controller.highlightLayers.count == 2, "Controller created an incorrect number of layers for underline. Expected 2, found \(controller.highlightLayers.count)")
         controller.setCursorPosition((1, 3))
         XCTAssert(controller.highlightLayers.isEmpty, "Controller failed to remove bracket pair layers.")
 

From 3ebaf9e27a6cb7b5b1365482dbf9dab8db3d0653 Mon Sep 17 00:00:00 2001
From: Khan Winter <35942988+thecoolwinter@users.noreply.github.com>
Date: Mon, 8 May 2023 12:33:03 -0500
Subject: [PATCH 6/7] Adjust underline Y value

---
 .../Controller/STTextViewController+HighlightRange.swift   | 5 +++--
 .../Controller/STTextViewController+Lifecycle.swift        | 3 +++
 .../CodeEditTextView/Controller/STTextViewController.swift | 7 ++++---
 3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift b/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift
index f71e05ed3..39dab99e5 100644
--- a/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift
+++ b/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift
@@ -144,8 +144,9 @@ extension STTextViewController {
             layer.frame = rectToHighlight
         case .underline:
             let path = CGMutablePath()
-            path.move(to: CGPoint(x: rectToHighlight.minX, y: rectToHighlight.maxY))
-            path.addLine(to: CGPoint(x: rectToHighlight.maxX, y: rectToHighlight.maxY))
+            let pathY = rectToHighlight.maxY - (lineHeight - font.lineHeight)/4
+            path.move(to: CGPoint(x: rectToHighlight.minX, y: pathY))
+            path.addLine(to: CGPoint(x: rectToHighlight.maxX, y: pathY))
             layer.path = path
         }
 
diff --git a/Sources/CodeEditTextView/Controller/STTextViewController+Lifecycle.swift b/Sources/CodeEditTextView/Controller/STTextViewController+Lifecycle.swift
index 4df7397d9..a1dfef35d 100644
--- a/Sources/CodeEditTextView/Controller/STTextViewController+Lifecycle.swift
+++ b/Sources/CodeEditTextView/Controller/STTextViewController+Lifecycle.swift
@@ -121,6 +121,9 @@ extension STTextViewController {
         ) { [weak self] _ in
             self?.removeHighlightLayers()
             self?.updateTextContainerWidthIfNeeded()
+            if self?.bracketPairHighlight != .flash {
+                self?.highlightSelectionPairs()
+            }
         }
 
         systemAppearance = NSApp.effectiveAppearance.name
diff --git a/Sources/CodeEditTextView/Controller/STTextViewController.swift b/Sources/CodeEditTextView/Controller/STTextViewController.swift
index 4785c6267..c77f63907 100644
--- a/Sources/CodeEditTextView/Controller/STTextViewController.swift
+++ b/Sources/CodeEditTextView/Controller/STTextViewController.swift
@@ -99,8 +99,6 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
     public var bracketPairHighlight: BracketPairHighlight? {
         didSet {
             removeHighlightLayers()
-            // Update selection highlights if needed.
-            highlightSelectionPairs()
         }
     }
 
@@ -227,6 +225,9 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
 
         highlighter?.invalidate()
         updateTextContainerWidthIfNeeded()
+        if bracketPairHighlight == .flash {
+            highlightSelectionPairs()
+        }
     }
 
     /// Calculated line height depending on ``STTextViewController/lineHeightMultiple``
@@ -242,7 +243,7 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
     // MARK: Selectors
 
     override public func keyDown(with event: NSEvent) {
-        if !highlightLayers.isEmpty {
+        if bracketPairHighlight == .flash &&  !highlightLayers.isEmpty {
             removeHighlightLayers()
         }
     }

From 59fe2b97ddeef757ecaf05cc5063961a52c71b4b Mon Sep 17 00:00:00 2001
From: Khan Winter <35942988+thecoolwinter@users.noreply.github.com>
Date: Mon, 8 May 2023 14:14:03 -0500
Subject: [PATCH 7/7] Fix flaky test, `removeHighlightLayers`

---
 ...t => STTextViewController+HighlightBracket.swift} |  1 +
 .../Controller/STTextViewController+Lifecycle.swift  |  6 ++----
 .../Controller/STTextViewController.swift            | 12 +++---------
 .../STTextViewControllerTests.swift                  |  1 +
 4 files changed, 7 insertions(+), 13 deletions(-)
 rename Sources/CodeEditTextView/Controller/{STTextViewController+HighlightRange.swift => STTextViewController+HighlightBracket.swift} (99%)

diff --git a/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift b/Sources/CodeEditTextView/Controller/STTextViewController+HighlightBracket.swift
similarity index 99%
rename from Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift
rename to Sources/CodeEditTextView/Controller/STTextViewController+HighlightBracket.swift
index 39dab99e5..848b6f15d 100644
--- a/Sources/CodeEditTextView/Controller/STTextViewController+HighlightRange.swift
+++ b/Sources/CodeEditTextView/Controller/STTextViewController+HighlightBracket.swift
@@ -12,6 +12,7 @@ extension STTextViewController {
     /// Highlights bracket pairs using the current selection.
     internal func highlightSelectionPairs() {
         guard bracketPairHighlight != nil else { return }
+        removeHighlightLayers()
         for selection in textView.textLayoutManager.textSelections.flatMap(\.textRanges) {
             if selection.isEmpty,
                let range = selection.nsRange(using: textView.textContentManager),
diff --git a/Sources/CodeEditTextView/Controller/STTextViewController+Lifecycle.swift b/Sources/CodeEditTextView/Controller/STTextViewController+Lifecycle.swift
index a1dfef35d..8cb55c110 100644
--- a/Sources/CodeEditTextView/Controller/STTextViewController+Lifecycle.swift
+++ b/Sources/CodeEditTextView/Controller/STTextViewController+Lifecycle.swift
@@ -109,7 +109,6 @@ extension STTextViewController {
             }
             self?.lastTextSelections = textSelections ?? []
 
-            self?.removeHighlightLayers()
             self?.updateCursorPosition()
             self?.highlightSelectionPairs()
         }
@@ -119,10 +118,9 @@ extension STTextViewController {
             object: (self.view as? NSScrollView)?.verticalRulerView,
             queue: .main
         ) { [weak self] _ in
-            self?.removeHighlightLayers()
             self?.updateTextContainerWidthIfNeeded()
-            if self?.bracketPairHighlight != .flash {
-                self?.highlightSelectionPairs()
+            if self?.bracketPairHighlight == .flash {
+                self?.removeHighlightLayers()
             }
         }
 
diff --git a/Sources/CodeEditTextView/Controller/STTextViewController.swift b/Sources/CodeEditTextView/Controller/STTextViewController.swift
index c77f63907..3d7915cda 100644
--- a/Sources/CodeEditTextView/Controller/STTextViewController.swift
+++ b/Sources/CodeEditTextView/Controller/STTextViewController.swift
@@ -96,11 +96,7 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
     }
 
     /// The type of highlight to use when highlighting bracket pairs. Leave as `nil` to disable highlighting.
-    public var bracketPairHighlight: BracketPairHighlight? {
-        didSet {
-            removeHighlightLayers()
-        }
-    }
+    public var bracketPairHighlight: BracketPairHighlight?
 
     /// The kern to use for characters. Defaults to `0.0` and is updated when `letterSpacing` is set.
     internal var kern: CGFloat = 0.0
@@ -225,9 +221,7 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
 
         highlighter?.invalidate()
         updateTextContainerWidthIfNeeded()
-        if bracketPairHighlight == .flash {
-            highlightSelectionPairs()
-        }
+        highlightSelectionPairs()
     }
 
     /// Calculated line height depending on ``STTextViewController/lineHeightMultiple``
@@ -243,7 +237,7 @@ public class STTextViewController: NSViewController, STTextViewDelegate, ThemeAt
     // MARK: Selectors
 
     override public func keyDown(with event: NSEvent) {
-        if bracketPairHighlight == .flash &&  !highlightLayers.isEmpty {
+        if bracketPairHighlight == .flash {
             removeHighlightLayers()
         }
     }
diff --git a/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift b/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift
index 9fd465b27..161299466 100644
--- a/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift
+++ b/Tests/CodeEditTextViewTests/STTextViewControllerTests.swift
@@ -222,6 +222,7 @@ final class STTextViewControllerTests: XCTestCase {
         controller.textView.string = "{ Loren Ipsum {} }"
         controller.setCursorPosition((1, 2)) // After first opening {
         XCTAssert(controller.highlightLayers.isEmpty, "Controller added highlight layer when setting is set to `nil`")
+        controller.setCursorPosition((1, 3))
 
         controller.bracketPairHighlight = .bordered(color: .black)
         controller.setCursorPosition((1, 2)) // After first opening {