Toggle comment for current line via CMD + /

Sources/CodeEditSourceEditor/Controller/TextViewController+LoadView.swift

@@ -109,5 +109,18 @@ extension TextViewController {
                 }
             }
             .store(in: &cancellables)
+
+        NSEvent.addLocalMonitorForEvents(matching: .keyDown) { event in
+            guard self.view.window?.firstResponder == self.textView else { return event }
+            let charactersIgnoringModifiers = event.charactersIgnoringModifiers
+            let commandKey = NSEvent.ModifierFlags.command.rawValue
+            let modifierFlags = event.modifierFlags.intersection(.deviceIndependentFlagsMask).rawValue
+            if modifierFlags == commandKey && event.charactersIgnoringModifiers == "/" {
+                self.commandSlashCalled()
+                return nil
+            } else {
+                return event
+            }
+        }
     }
 }

Sources/CodeEditSourceEditor/Controller/TextViewController+Shortcuts.swift

@@ -0,0 +1,92 @@
+//
+//  TextViewController+Shortcuts.swift
+//  CodeEditSourceEditor
+//
+//  Created by Sophia Hooley on 4/21/24.
+//
+
+import CodeEditTextView
+import AppKit
+
+extension TextViewController {
+    /// Method called when CMD + / key sequence recognized, comments cursor's current line of code
+    public func commandSlashCalled() {
+        guard let cursorPosition = cursorPositions.first else {
+            print("There is no cursor \(#function)")
+            return
+        }
+        // Many languages require a character sequence at the beginning of the line to comment the line.
+        // (ex. python #, C++ //)
+        // If such a sequence exists, we will insert that sequence at the beginning of the line
+        if !language.lineCommentString.isEmpty {
+            toggleCharsAtBeginningOfLine(chars: language.lineCommentString, lineNumber: cursorPosition.line)
+        }
+        // In other cases, languages require a character sequence at beginning and end of a line, aka a range comment
+        // (Ex. HTML <!--line here -->)
+        // We treat the line as a one-line range to comment it out using rangeCommentStrings on both sides of the line
+        else {
+            let (openComment, closeComment) = language.rangeCommentStrings
+            toggleCharsAtEndOfLine(chars: closeComment, lineNumber: cursorPosition.line)
+            toggleCharsAtBeginningOfLine(chars: openComment, lineNumber: cursorPosition.line)
+        }
+    }
+
+    ///  Toggles comment string at the beginning of a specified line (lineNumber is 1-indexed)
+    private func toggleCharsAtBeginningOfLine(chars: String, lineNumber: Int) {
+        guard let lineInfo = textView.layoutManager.textLineForIndex(lineNumber - 1) else {
+            print("There are no characters/lineInfo \(#function)")
+            return
+        }
+        guard let lineString = textView.textStorage.substring(from: lineInfo.range) else {
+            print("There are no characters/lineString \(#function)")
+            return
+        }
+        let firstNonWhiteSpaceCharIndex = lineString.firstIndex(where: {!$0.isWhitespace}) ?? lineString.startIndex
+        let numWhitespaceChars = lineString.distance(from: lineString.startIndex, to: firstNonWhiteSpaceCharIndex)
+        let firstCharsInLine = lineString.suffix(from: firstNonWhiteSpaceCharIndex).prefix(chars.count)
+        // toggle comment off
+        if firstCharsInLine == chars {
+            textView.replaceCharacters(in: NSRange(
+                location: lineInfo.range.location + numWhitespaceChars,
+                length: chars.count
+            ), with: "")
+        }
+        // toggle comment on
+        else {
+            textView.replaceCharacters(in: NSRange(
+                location: lineInfo.range.location + numWhitespaceChars,
+                length: 0
+            ), with: chars)
+        }
+    }
+
+    ///  Toggles a specific string of characters at the end of a specified line. (lineNumber is 1-indexed)
+    private func toggleCharsAtEndOfLine(chars: String, lineNumber: Int) {
+        guard let lineInfo = textView.layoutManager.textLineForIndex(lineNumber - 1) else {
+            print("There are no characters/lineInfo \(#function)")
+            return
+        }
+        guard let lineString = textView.textStorage.substring(from: lineInfo.range) else {
+            print("There are no characters/lineString \(#function)")
+            return
+        }
+        let lineLastCharIndex = lineInfo.range.location + lineInfo.range.length - 1
+        let closeCommentLength = chars.count
+        let closeCommentRange = NSRange(
+            location: lineLastCharIndex - closeCommentLength,
+            length: closeCommentLength
+        )
+        let lastCharsInLine = textView.textStorage.substring(from: closeCommentRange)
+        // toggle comment off
+        if lastCharsInLine == chars {
+            textView.replaceCharacters(in: NSRange(
+                location: lineLastCharIndex - closeCommentLength,
+                length: closeCommentLength
+            ), with: "")
+        }
+        // toggle comment on
+        else {
+            textView.replaceCharacters(in: NSRange(location: lineLastCharIndex, length: 0), with: chars)
+        }
+    }
+}

Sources/CodeEditSourceEditor/Controller/TextViewController.swift

@@ -16,7 +16,6 @@ import TextFormation
 ///
 /// A view controller class for managing a source editor. Uses ``CodeEditTextView/TextView`` for input and rendering,
 /// tree-sitter for syntax highlighting, and TextFormation for live editing completions.
-/// 
 public class TextViewController: NSViewController {
     // swiftlint:disable:next line_length
     public static let cursorPositionUpdatedNotification: Notification.Name = .init("TextViewController.cursorPositionNotification")