Preserve inline code backgrounds after wrapping

Draw inline code fills from glyph positions because TextKit can report zero-width bounds after hidden delimiters wrap.

Co-authored-by: Codex <codex@openai.com>

Author: afollestad

Sources/BlockInputKit/AppKit/BlockInputTextView+InlineCode.swift

@@ -0,0 +1,50 @@
+import AppKit
+
+extension BlockInputTextView {
+    /// TextKit can report zero-width bounds and omit native backgrounds when hidden delimiters wrap.
+    /// Keep valid bounds for bidirectional runs; glyph positions recover the empty rectangles.
+    func drawInlineCodeBackgrounds(in dirtyRect: NSRect) {
+        guard let textStorage, let layoutManager, let textContainer else {
+            return
+        }
+        layoutManager.ensureLayout(for: textContainer)
+        let origin = textContainerOrigin
+        let fullRange = NSRange(location: 0, length: textStorage.length)
+        textStorage.enumerateAttribute(.blockInputInlineCodeBackground, in: fullRange) { value, range, _ in
+            guard let color = value as? NSColor else {
+                return
+            }
+            let glyphRange = layoutManager.glyphRange(forCharacterRange: range, actualCharacterRange: nil)
+            color.setFill()
+            var glyphIndex = glyphRange.location
+            while glyphIndex < NSMaxRange(glyphRange) {
+                var lineRange = NSRange()
+                let lineRect = layoutManager.blockInputGlyphLineRect(forGlyphAt: glyphIndex, effectiveRange: &lineRange)
+                let intersection = NSIntersectionRange(glyphRange, lineRange)
+                var rect = layoutManager.boundingRect(forGlyphRange: intersection, in: textContainer)
+                if rect.width <= 0 {
+                    let fragmentRect = layoutManager.lineFragmentRect(forGlyphAt: glyphIndex, effectiveRange: nil)
+                    let startX = fragmentRect.minX + layoutManager.location(forGlyphAt: intersection.location).x
+                    let endIndex = NSMaxRange(intersection)
+                    let endX = endIndex < NSMaxRange(lineRange)
+                        ? fragmentRect.minX + layoutManager.location(forGlyphAt: endIndex).x
+                        : lineRect.maxX
+                    rect.origin.x = min(startX, endX)
+                    rect.size.width = abs(endX - startX)
+                }
+                rect.origin.y = lineRect.minY
+                rect.size.height = lineRect.height
+                rect = rect.offsetBy(dx: origin.x, dy: origin.y)
+                if rect.intersects(dirtyRect) {
+                    rect.fill()
+                }
+                glyphIndex = max(glyphIndex + 1, NSMaxRange(lineRange))
+            }
+        }
+    }
+}
+
+extension NSAttributedString.Key {
+    /// Keeps inline code fills out of TextKit's unreliable native background drawing around hidden delimiters.
+    static let blockInputInlineCodeBackground = NSAttributedString.Key("BlockInputInlineCodeBackground")
+}

Sources/BlockInputKit/AppKit/BlockInputTextView+Links.swift

@@ -13,6 +13,7 @@ struct BlockInputLinkHitResult {
 extension BlockInputTextView {
     override func draw(_ dirtyRect: NSRect) {
         drawInlineChipBackgrounds(in: dirtyRect)
+        drawInlineCodeBackgrounds(in: dirtyRect)
         super.draw(dirtyRect)
         // Images paint after super so selection highlight cannot wash them out.
         drawInlineImages(in: dirtyRect)

Sources/BlockInputKit/AppKit/BlockItem/BlockInputBlockItem+Formatting.swift

@@ -286,6 +286,7 @@ extension BlockInputBlockItem {
         textStorage.removeAttribute(.blockInputInlineImage, range: fullRange)
         textStorage.removeAttribute(.blockInputHiddenDelimiter, range: fullRange)
         textStorage.removeAttribute(.blockInputInlineCode, range: fullRange)
+        textStorage.removeAttribute(.blockInputInlineCodeBackground, range: fullRange)
         textStorage.removeAttribute(.paragraphStyle, range: fullRange)
         applyBaseParagraphStyle(for: block, textStorage: textStorage, range: fullRange)
         applyCodeBlockAttributes(for: block, textStorage: textStorage)
@@ -314,7 +315,7 @@ extension BlockInputBlockItem {
         if isInlineCodeSelection {
             attributes[.font] = inlineCodeFont(for: font)
             attributes[.foregroundColor] = inlineCodeForegroundColor()
-            attributes[.backgroundColor] = inlineCodeBackgroundColor()
+            attributes[.blockInputInlineCodeBackground] = inlineCodeBackgroundColor()
             attributes[.blockInputInlineCode] = true
         } else {
             attributes = Self.applyingInlineMarkdownStyles(
@@ -354,7 +355,7 @@ extension BlockInputBlockItem {
         for key: NSAttributedString.Key in [
             .foregroundColor, .backgroundColor, .underlineStyle, .strikethroughStyle, .link, .toolTip, .kern,
             .baselineOffset, .blockInputInlineChip, .blockInputInlineImage, .blockInputHiddenDelimiter,
-            .blockInputInlineCode
+            .blockInputInlineCode, .blockInputInlineCodeBackground
         ] {
             attributes.removeValue(forKey: key)
         }

Sources/BlockInputKit/AppKit/BlockItem/BlockInputBlockItem+InlineCode.swift

@@ -22,7 +22,7 @@ extension BlockInputBlockItem {
                     [
                         .font: inlineFont,
                         .foregroundColor: foregroundColor,
-                        .backgroundColor: backgroundColor
+                        .blockInputInlineCodeBackground: backgroundColor
                     ],
                     range: contentRange
                 )