custom layout manager with code block backgrounds and checkbox rendering

src/EditorView.swift

@@ -13,6 +13,7 @@ class MarkdownLayoutManager: NSLayoutManager {
         case codeBlock
         case blockquote
         case horizontalRule
+        case checkbox(checked: Bool)
         case tableBlock(columns: Int)
     }
 
@@ -34,12 +35,45 @@ class MarkdownLayoutManager: NSLayoutManager {
                 drawBlockquoteBorder(glyphRange: glyphRange, origin: origin, container: textContainer)
             case .horizontalRule:
                 drawHorizontalRule(glyphRange: glyphRange, origin: origin, container: textContainer)
-            case .tableBlock(let columns):
-                drawTableBorders(glyphRange: glyphRange, columns: columns, origin: origin, container: textContainer)
+            case .checkbox, .tableBlock:
+                break
             }
         }
     }
 
+    override func drawGlyphs(forGlyphRange glyphsToShow: NSRange, at origin: NSPoint) {
+        guard let textContainer = textContainers.first else {
+            super.drawGlyphs(forGlyphRange: glyphsToShow, at: origin)
+            return
+        }
+
+        var skipRanges: [NSRange] = []
+        for block in blockRanges {
+            guard case .checkbox(let checked) = block.kind else { continue }
+            let glyphRange = self.glyphRange(forCharacterRange: block.range, actualCharacterRange: nil)
+            guard NSIntersectionRange(glyphRange, glyphsToShow).length > 0 else { continue }
+            skipRanges.append(glyphRange)
+            drawCheckbox(checked: checked, glyphRange: glyphRange, origin: origin, container: textContainer)
+        }
+
+        if skipRanges.isEmpty {
+            super.drawGlyphs(forGlyphRange: glyphsToShow, at: origin)
+            return
+        }
+
+        skipRanges.sort { $0.location < $1.location }
+        var cursor = glyphsToShow.location
+        for skip in skipRanges {
+            if cursor < skip.location {
+                super.drawGlyphs(forGlyphRange: NSRange(location: cursor, length: skip.location - cursor), at: origin)
+            }
+            cursor = NSMaxRange(skip)
+        }
+        if cursor < NSMaxRange(glyphsToShow) {
+            super.drawGlyphs(forGlyphRange: NSRange(location: cursor, length: NSMaxRange(glyphsToShow) - cursor), at: origin)
+        }
+    }
+
     private func drawCodeBlockBackground(glyphRange: NSRange, origin: NSPoint, container: NSTextContainer) {
         var rect = boundingRect(forGlyphRange: glyphRange, in: container)
         rect.origin.x = origin.x + 4
@@ -82,6 +116,34 @@ class MarkdownLayoutManager: NSLayoutManager {
         path.stroke()
     }
 
+    private func drawCheckbox(checked: Bool, glyphRange: NSRange, origin: NSPoint, container: NSTextContainer) {
+        let rect = boundingRect(forGlyphRange: glyphRange, in: container)
+        let size: CGFloat = 14
+        let x = rect.origin.x + origin.x
+        let y = rect.origin.y + origin.y + (rect.size.height - size) / 2
+        let boxRect = NSRect(x: x, y: y, width: size, height: size)
+        let path = NSBezierPath(roundedRect: boxRect, xRadius: 3, yRadius: 3)
+
+        if checked {
+            Theme.current.green.setFill()
+            path.fill()
+
+            let check = NSBezierPath()
+            check.move(to: NSPoint(x: x + 3, y: y + size / 2))
+            check.line(to: NSPoint(x: x + size * 0.4, y: y + 3))
+            check.line(to: NSPoint(x: x + size - 3, y: y + size - 3))
+            check.lineWidth = 2
+            check.lineCapStyle = .round
+            check.lineJoinStyle = .round
+            NSColor.white.setStroke()
+            check.stroke()
+        } else {
+            Theme.current.overlay0.setStroke()
+            path.lineWidth = 1.5
+            path.stroke()
+        }
+    }
+
     private func drawTableBorders(glyphRange: NSRange, columns: Int, origin: NSPoint, container: NSTextContainer) {
         guard columns > 0 else { return }
         var rect = boundingRect(forGlyphRange: glyphRange, in: container)
@@ -100,7 +162,6 @@ class MarkdownLayoutManager: NSLayoutManager {
         let tableText = text.substring(with: charRange)
         let lines = tableText.components(separatedBy: "\n").filter { !$0.isEmpty }
 
-        // Draw horizontal row separators
         var charOffset = charRange.location
         for (i, line) in lines.enumerated() {
             let lineLen = (line as NSString).length
@@ -118,7 +179,6 @@ class MarkdownLayoutManager: NSLayoutManager {
             charOffset += lineLen + 1
         }
 
-        // Draw vertical column separators using pipe character glyph positions
         if let firstLine = lines.first {
             let nsFirstLine = firstLine as NSString
             var pipeOffsets: [Int] = []
@@ -127,7 +187,6 @@ class MarkdownLayoutManager: NSLayoutManager {
                     pipeOffsets.append(i)
                 }
             }
-            // Skip first and last pipe (outer borders), draw inner separators
             if pipeOffsets.count > 2 {
                 for pi in 1..<(pipeOffsets.count - 1) {
                     let charPos = charRange.location + pipeOffsets[pi]
@@ -143,7 +202,6 @@ class MarkdownLayoutManager: NSLayoutManager {
                 }
             }
 
-            // Header background
             if lines.count > 1 {
                 let firstLineRange = NSRange(location: charRange.location, length: nsFirstLine.length)
                 let headerGlyphRange = self.glyphRange(forCharacterRange: firstLineRange, actualCharacterRange: nil)
@@ -418,6 +476,10 @@ struct EditorTextView: NSViewRepresentable {
 
 // MARK: - Block Range Detection
 
+private let checkboxPattern: NSRegularExpression? = {
+    try? NSRegularExpression(pattern: "\\[[ xX]\\]")
+}()
+
 func updateBlockRanges(for textView: NSTextView) {
     guard let lm = textView.layoutManager as? MarkdownLayoutManager else { return }
     let text = textView.string as NSString
@@ -440,7 +502,6 @@ func updateBlockRanges(for textView: NSTextView) {
         let line = text.substring(with: lineRange)
         let trimmed = line.trimmingCharacters(in: .whitespacesAndNewlines)
 
-        // Fenced code blocks
         if openFence == nil && trimmed.hasPrefix("```") {
             openFence = lineRange.location
         } else if openFence != nil && trimmed == "```" {
@@ -456,7 +517,6 @@ func updateBlockRanges(for textView: NSTextView) {
             continue
         }
 
-        // Blockquotes
         if trimmed.hasPrefix("> ") || trimmed == ">" {
             if blockquoteStart == nil { blockquoteStart = lineRange.location }
             blockquoteEnd = NSMaxRange(lineRange)
@@ -467,12 +527,24 @@ func updateBlockRanges(for textView: NSTextView) {
             }
         }
 
-        // Horizontal rules
         if isHorizontalRule(trimmed) && openFence == nil {
             blocks.append(.init(range: lineRange, kind: .horizontalRule))
         }
 
-        // Tables
+        // Task list checkboxes
+        let taskPrefixes = ["- [ ] ", "- [x] ", "- [X] ", "* [ ] ", "* [x] ", "* [X] ", "+ [ ] ", "+ [x] ", "+ [X] "]
+        let strippedLine = trimmed
+        for prefix in taskPrefixes {
+            if strippedLine.hasPrefix(prefix) {
+                let checked = prefix.contains("x") || prefix.contains("X")
+                if let regex = checkboxPattern,
+                   let match = regex.firstMatch(in: text as String, range: lineRange) {
+                    blocks.append(.init(range: match.range, kind: .checkbox(checked: checked)))
+                }
+                break
+            }
+        }
+
         if trimmed.hasPrefix("|") {
             if tableStart == nil {
                 tableStart = lineRange.location
@@ -491,7 +563,6 @@ func updateBlockRanges(for textView: NSTextView) {
         lineStart = NSMaxRange(lineRange)
     }
 
-    // Flush pending blocks
     if let start = blockquoteStart {
         blocks.append(.init(range: NSRange(location: start, length: blockquoteEnd - start), kind: .blockquote))
     }