拼写输入框支持水平滚动，避免长单词被压缩

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

LearnEnglish/LearnEnglish/Views/SpellingInputView.swift

@@ -20,18 +20,31 @@ final class SpellingInputView: UIView, UITextFieldDelegate {
 
     override init(frame: CGRect) {
         super.init(frame: frame)
+
+        let scrollView = UIScrollView()
+        scrollView.showsHorizontalScrollIndicator = false
+        scrollView.showsVerticalScrollIndicator = false
+        addSubview(scrollView)
+        scrollView.translatesAutoresizingMaskIntoConstraints = false
+        NSLayoutConstraint.activate([
+            scrollView.topAnchor.constraint(equalTo: topAnchor),
+            scrollView.bottomAnchor.constraint(equalTo: bottomAnchor),
+            scrollView.leadingAnchor.constraint(equalTo: leadingAnchor),
+            scrollView.trailingAnchor.constraint(equalTo: trailingAnchor)
+        ])
+
         stack.axis = .horizontal
         stack.spacing = 6
         stack.alignment = .center
         stack.isUserInteractionEnabled = true
-        addSubview(stack)
+        scrollView.addSubview(stack)
         stack.translatesAutoresizingMaskIntoConstraints = false
         NSLayoutConstraint.activate([
-            stack.topAnchor.constraint(equalTo: topAnchor),
-            stack.bottomAnchor.constraint(equalTo: bottomAnchor),
-            stack.centerXAnchor.constraint(equalTo: centerXAnchor),
-            stack.leadingAnchor.constraint(greaterThanOrEqualTo: leadingAnchor),
-            stack.trailingAnchor.constraint(lessThanOrEqualTo: trailingAnchor)
+            stack.topAnchor.constraint(equalTo: scrollView.contentLayoutGuide.topAnchor),
+            stack.bottomAnchor.constraint(equalTo: scrollView.contentLayoutGuide.bottomAnchor),
+            stack.leadingAnchor.constraint(equalTo: scrollView.contentLayoutGuide.leadingAnchor),
+            stack.trailingAnchor.constraint(equalTo: scrollView.contentLayoutGuide.trailingAnchor),
+            stack.heightAnchor.constraint(equalTo: scrollView.frameLayoutGuide.heightAnchor)
         ])
 
         hiddenField.delegate = self
@@ -126,17 +139,9 @@ final class SpellingInputView: UIView, UITextFieldDelegate {
 
     private func rebuildBoxes() {
         stack.arrangedSubviews.forEach { $0.removeFromSuperview() }
-        let count = CGFloat(max(chars.count, 1))
-        let available = (window?.screen.bounds.width ?? 390) - 32
-        var spacing: CGFloat = 6
-        var boxWidth = (available - spacing * (count - 1)) / count
-        if boxWidth < 16 {
-            spacing = 3
-            boxWidth = (available - spacing * (count - 1)) / count
-        }
-        boxWidth = min(36, boxWidth)
-        stack.spacing = spacing
-        let fontSize = min(22, max(12, boxWidth * 0.62))
+        let boxWidth: CGFloat = 32
+        let fontSize: CGFloat = 20
+        stack.spacing = 6
         boxViews = chars.enumerated().map { index, ch in
             let box = makeBox(fontSize: fontSize)
             box.tag = index