fix(mobile): show complete unwrapped diff lines containing tabs

apps/mobile/modules/t3-review-diff/ios/ReviewDiffCodeLayout.swift

@@ -1,7 +1,10 @@
 import UIKit
 
 /// ASCII uses fixed-pitch columns. TextKit handles shaping, tabs, and Unicode highlights.
+/// Pass `unboundedWidth` to lay a row out on one line for horizontal scrolling.
 final class ReviewDiffCodeLayout: NSObject {
+  static let unboundedWidth = CGFloat.greatestFiniteMagnitude
+
   // Measurement reuses one engine; only recently drawn rows retain a full TextKit layout.
   private static var measurer: ReviewDiffTextLayout {
     let key = "T3ReviewDiff.textMeasurer"
@@ -20,6 +23,8 @@ final class ReviewDiffCodeLayout: NSObject {
   let lineHeight: CGFloat
   let firstLineHeight: CGFloat
   let extraHeight: CGFloat
+  /// Widest visual line, which sizes horizontal scrolling when the row is not wrapped.
+  let usedWidth: CGFloat
   private let font: UIFont
   private let width: CGFloat
   private let characterWidth: CGFloat
@@ -32,10 +37,12 @@ final class ReviewDiffCodeLayout: NSObject {
     self.characterWidth = characterWidth
     lineHeight = ceil(font.lineHeight)
     if text.utf8.allSatisfy({ $0 >= 32 && $0 <= 126 }) {
-      let columns = max(1, Int(width / characterWidth))
-      starts = Array(stride(from: 0, to: max(1, text.utf8.count), by: columns))
+      let length = max(1, text.utf8.count)
+      let columns = max(1, Int(min(width / characterWidth, CGFloat(length))))
+      starts = Array(stride(from: 0, to: length, by: columns))
       firstLineHeight = font.lineHeight
       extraHeight = CGFloat(starts.count - 1) * lineHeight
+      usedWidth = CGFloat(min(text.utf8.count, columns)) * characterWidth
       usesNativeLayout = false
     } else {
       let layout = Self.measurer
@@ -46,7 +53,9 @@ final class ReviewDiffCodeLayout: NSObject {
       starts = [0]
       firstLineHeight = manager.numberOfGlyphs > 0
         ? manager.lineFragmentRect(forGlyphAt: 0, effectiveRange: nil).height : font.lineHeight
-      extraHeight = max(0, manager.usedRect(for: container).height - firstLineHeight)
+      let used = manager.usedRect(for: container)
+      extraHeight = max(0, used.height - firstLineHeight)
+      usedWidth = ceil(used.width)
     }
   }
 

apps/mobile/modules/t3-review-diff/ios/T3ReviewDiffView.swift

@@ -1120,6 +1120,14 @@ private final class ReviewDiffContentView: UIView, UIGestureRecognizerDelegate {
     ceil(codeFont.lineHeight)
   }
 
+  /// Wrapped rows fill the code viewport; unwrapped rows keep one line and scroll horizontally.
+  private func codeLayoutWidthLimit(font: UIFont) -> CGFloat? {
+    guard style.wordWrap else { return ReviewDiffCodeLayout.unboundedWidth }
+    let width = viewportWidth - codeStartX - style.codePadding
+    let characterWidth = monospaceCharacterWidth(font: font)
+    return characterWidth > 0 && width >= characterWidth ? width : nil
+  }
+
   func frameForRow(at index: Int) -> CGRect? {
     guard rows.indices.contains(index), rowOffsets.indices.contains(index) else {
       return nil
@@ -1141,9 +1149,8 @@ private final class ReviewDiffContentView: UIView, UIGestureRecognizerDelegate {
     completion: @escaping () -> Void
   ) {
     let font = codeFont
-    let width = viewportWidth - codeStartX - style.codePadding
     let characterWidth = monospaceCharacterWidth(font: font)
-    guard style.wordWrap, width >= characterWidth, characterWidth > 0 else {
+    guard let width = codeLayoutWidthLimit(font: font) else {
       completion()
       return
     }
@@ -1160,7 +1167,7 @@ private final class ReviewDiffContentView: UIView, UIGestureRecognizerDelegate {
       }
       DispatchQueue.main.async { [weak self] in
         guard let self, isCurrent() else { return }
-        if self.codeFont != font || self.viewportWidth - self.codeStartX - self.style.codePadding != width {
+        if self.codeFont != font || self.codeLayoutWidthLimit(font: font) != width {
           self.prepareRows(rows, on: queue, isCurrent: isCurrent, completion: completion)
           return
         }
@@ -1176,18 +1183,16 @@ private final class ReviewDiffContentView: UIView, UIGestureRecognizerDelegate {
     var nextOffsets: [CGFloat] = []
     var nextFileHeaderRowIndices: [Int] = []
     nextOffsets.reserveCapacity(rows.count)
-    var maxColumnCountsByFileId: [String: Int] = [:]
+    var maxWidthsByFileId: [String: CGFloat] = [:]
     var nextCodeLayouts: [String: ReviewDiffCodeLayout] = [:]
     var offset: CGFloat = 0
     let font = codeFont
     let characterWidth = monospaceCharacterWidth(font: font)
-    let wrapAvailableWidth = viewportWidth - codeStartX - style.codePadding
-    let wrapColumns = style.wordWrap && characterWidth > 0 && wrapAvailableWidth >= characterWidth
-      ? Int(wrapAvailableWidth / characterWidth)
-      : nil
-    if codeLayoutWidth != wrapAvailableWidth || codeLayoutFont != font {
+    let layoutWidth = codeLayoutWidthLimit(font: font)
+    let wrapColumns = style.wordWrap ? layoutWidth.map { Int($0 / characterWidth) } : nil
+    if let layoutWidth, codeLayoutWidth != layoutWidth || codeLayoutFont != font {
       codeLayoutsByRowId.removeAll()
-      codeLayoutWidth = wrapAvailableWidth
+      codeLayoutWidth = layoutWidth
       codeLayoutFont = font
     }
 
@@ -1202,27 +1207,30 @@ private final class ReviewDiffContentView: UIView, UIGestureRecognizerDelegate {
       switch row.kind {
       case "line":
         // UTF-16 columns match the word diff ranges and the segments drawCodeLines draws.
-        let columnCount = row.content?.utf16.count ?? 0
-        maxColumnCountsByFileId[fileId] = max(maxColumnCountsByFileId[fileId] ?? 0, columnCount)
-        if wrapColumns != nil, let content = row.content {
+        var width = CGFloat(row.content?.utf16.count ?? 0) * characterWidth
+        if let layoutWidth, let content = row.content {
           let cached = codeLayoutsByRowId[row.id]
           let layout: ReviewDiffCodeLayout
           if let cached, cached.text == content {
             layout = cached
           } else {
             layout = ReviewDiffCodeLayout(
-              text: content, font: font, width: wrapAvailableWidth, characterWidth: characterWidth
+              text: content, font: font, width: layoutWidth, characterWidth: characterWidth
             )
           }
           nextCodeLayouts[row.id] = layout
+          // Tabs and fallback glyphs are wider than one column.
+          width = layout.usedWidth
           if rowHeight > 0 {
             rowHeight = max(rowHeight, layout.firstLineHeight) + layout.extraHeight
           }
         }
+        maxWidthsByFileId[fileId] = max(maxWidthsByFileId[fileId] ?? 0, width)
       case "hunk":
-        maxColumnCountsByFileId[fileId] = max(
-          maxColumnCountsByFileId[fileId] ?? 0,
-          row.text?.utf16.count ?? 0
+        // Hunk context can hold tabs and draws in its own font, so measure what drawHunkRow draws.
+        maxWidthsByFileId[fileId] = max(
+          maxWidthsByFileId[fileId] ?? 0,
+          textWidth(row.text ?? "", font: hunkFont)
         )
       default:
         break
@@ -1233,10 +1241,8 @@ private final class ReviewDiffContentView: UIView, UIGestureRecognizerDelegate {
     codeCharacterWidth = characterWidth
     codeWrapColumns = wrapColumns
     codeLayoutsByRowId = nextCodeLayouts
-    contentWidthsByFileId = maxColumnCountsByFileId.mapValues { maxColumnCount in
-      let measuredWidth = ceil(CGFloat(maxColumnCount) * characterWidth) + style.codePadding * 2
-      return max(0, min(style.contentWidth, measuredWidth))
-    }
+    // Measured widths are not capped, so the end of every line stays reachable by scrolling.
+    contentWidthsByFileId = maxWidthsByFileId.mapValues { ceil($0) + style.codePadding * 2 }
     rowOffsets = nextOffsets
     fileHeaderRowIndices = nextFileHeaderRowIndices
     contentHeight = offset
@@ -2375,7 +2381,7 @@ private final class ReviewDiffContentView: UIView, UIGestureRecognizerDelegate {
         version: codeDecorationVersion
       )
       layout.draw(
-        at: CGPoint(x: codeStartX, y: rect.minY + max(0, (firstLineRect.height - layout.firstLineHeight) / 2)),
+        at: CGPoint(x: codeStartX - horizontalOffset, y: rect.minY + max(0, (firstLineRect.height - layout.firstLineHeight) / 2)),
         clip: context.boundingBoxOfClipPath
       )
       context.restoreGState()

apps/mobile/modules/t3-review-diff/tests/ios/main.swift

@@ -46,6 +46,39 @@ for fixture in fixtures {
     cases += 1
   }
 }
+// Unwrapped rows stay on one line, and their measured width covers every drawn glyph.
+for text in ["\t\t\"extends\": \"@riptech/tsconfig/tsconfig.test.json\",", "漢字\tvalue", "مرحبا\tvalue"] {
+  let layout = ReviewDiffCodeLayout(
+    text: text, font: font, width: ReviewDiffCodeLayout.unboundedWidth, characterWidth: characterWidth
+  )
+  check(layout.usesNativeLayout && layout.extraHeight == 0, "Unwrapped text must stay on one line: \(text)")
+  check(layout.usedWidth > CGFloat(text.utf16.count - 1) * characterWidth, "Tabs must widen the row: \(text)")
+  layout.decorate(text: NSAttributedString(string: text, attributes: [.foregroundColor: UIColor.black]), highlights: [], color: .clear, version: 0)
+  let format = UIGraphicsImageRendererFormat()
+  format.scale = 1
+  format.opaque = false
+  format.preferredRange = .standard
+  let size = CGSize(width: layout.usedWidth + 40, height: ceil(layout.firstLineHeight))
+  let image = UIGraphicsImageRenderer(size: size, format: format).image { _ in
+    layout.draw(at: .zero, clip: CGRect(origin: .zero, size: size))
+  }
+  let bitmap = image.cgImage!
+  let bytes = CFDataGetBytePtr(bitmap.dataProvider!.data!)!
+  var inkMaxX = -1
+  for y in 0..<bitmap.height {
+    for x in 0..<bitmap.width where bytes[y * bitmap.bytesPerRow + x * 4 + 3] != 0 {
+      inkMaxX = max(inkMaxX, x)
+    }
+  }
+  check(inkMaxX <= Int(layout.usedWidth) + 1, "Ink beyond measured width: \(text) x=\(inkMaxX)")
+  check(CGFloat(inkMaxX) >= layout.usedWidth - characterWidth * 2, "Row end was not drawn: \(text) x=\(inkMaxX)")
+  cases += 1
+}
+let unwrappedAscii = ReviewDiffCodeLayout(
+  text: "const value = 123;", font: font, width: ReviewDiffCodeLayout.unboundedWidth, characterWidth: characterWidth
+)
+check(unwrappedAscii.starts == [0] && unwrappedAscii.usedWidth == 18 * characterWidth)
+
 let ascii = String(repeating: "const value = 123; ", count: 100)
 let layout = ReviewDiffCodeLayout(text: ascii, font: font, width: 280, characterWidth: characterWidth)
 let string = ascii as NSString
@@ -57,4 +90,4 @@ for (index, start) in layout.starts.enumerated() {
   reconstructed += segment
 }
 check(reconstructed == ascii)
-print("Passed \(cases) Unicode/width cases, color-update geometry, and ASCII coverage")
+print("Passed \(cases) Unicode/width and unwrapped cases, color-update geometry, and ASCII coverage")