refactor: remove HighlightedTextarea (cursor desync unfixable)

src/components/ChatInput.tsx

@@ -1,7 +1,6 @@
 import { useState, useRef, useEffect, useCallback, lazy, Suspense } from 'react';
-import { Send, Square, Paperclip, X, FileText, Eye, EyeOff, Highlighter } from 'lucide-react';
+import { Send, Square, Paperclip, X, FileText, Eye, EyeOff } from 'lucide-react';
 import { useT } from '../hooks/useLocale';
-import { HighlightedTextarea } from './HighlightedTextarea';
 
 const ReactMarkdown = lazy(() => import('react-markdown'));
 const remarkGfm = import('remark-gfm').then(m => m.default);
@@ -92,7 +91,6 @@ export function ChatInput({ onSend, onAbort, isGenerating, disabled, sessionKey
   const [files, setFiles] = useState<FileAttachment[]>([]);
   const [isDragOver, setIsDragOver] = useState(false);
   const [showPreview, setShowPreview] = useState(() => localStorage.getItem('pinchchat-md-preview') === '1');
-  const [highlightEnabled, setHighlightEnabled] = useState(() => localStorage.getItem('pinchchat-syntax-hl') === '1');
   const textareaRef = useRef<HTMLTextAreaElement>(null);
   const fileInputRef = useRef<HTMLInputElement>(null);
 
@@ -285,15 +283,6 @@ export function ChatInput({ onSend, onAbort, isGenerating, disabled, sessionKey
             >
               {showPreview ? <EyeOff size={18} /> : <Eye size={18} />}
             </button>
-            {/* Syntax highlight toggle — hidden on mobile */}
-            <button
-              onClick={() => setHighlightEnabled(v => { const next = !v; localStorage.setItem('pinchchat-syntax-hl', next ? '1' : '0'); return next; })}
-              className={`hidden sm:flex shrink-0 h-11 w-11 rounded-2xl border border-pc-border bg-pc-elevated/30 items-center justify-center transition-colors ${highlightEnabled ? 'text-pc-accent-light bg-[var(--pc-accent-glow)]' : 'text-pc-text-secondary hover:text-pc-accent-light hover:bg-[var(--pc-hover)]'}`}
-              title={highlightEnabled ? 'Disable syntax highlight' : 'Enable syntax highlight'}
-              aria-label={highlightEnabled ? 'Disable syntax highlight' : 'Enable syntax highlight'}
-            >
-              <Highlighter size={18} />
-            </button>
             <input
               ref={fileInputRef}
               type="file"
@@ -303,12 +292,11 @@ export function ChatInput({ onSend, onAbort, isGenerating, disabled, sessionKey
               accept="image/*,.pdf,.txt,.md,.json,.csv,.log,.py,.js,.ts,.tsx,.jsx,.html,.css,.yaml,.yml,.xml,.sql,.sh,.env,.toml"
             />
 
-            <HighlightedTextarea
+            <textarea
               id="chat-input"
               ref={textareaRef}
               value={text}
-              highlightEnabled={highlightEnabled}
-              onChange={(e) => setText((e.target as HTMLTextAreaElement).value)}
+              onChange={(e) => setText(e.target.value)}
               onKeyDown={handleKeyDown}
               onPaste={handlePaste}
               placeholder={t('chat.inputPlaceholder')}

src/components/HighlightedTextarea.tsx

@@ -1,97 +0,0 @@
-import { forwardRef, useRef, useEffect, useImperativeHandle, useCallback } from 'react';
-
-/**
- * A textarea with a syntax-highlighted backdrop overlay.
- * The textarea text is transparent; a <pre> behind it renders colored tokens.
- */
-
-interface Props extends Omit<React.TextareaHTMLAttributes<HTMLTextAreaElement>, 'style'> {
-  value: string;
-  highlightEnabled?: boolean;
-}
-
-// Simple markdown tokenizer — returns HTML with <span> wrappers
-function highlightMarkdown(text: string): string {
-  if (!text) return '\n'; // pre needs at least a newline to size correctly
-
-  // Escape HTML first
-  let html = text
-    .replace(/&/g, '&amp;')
-    .replace(/</g, '&lt;')
-    .replace(/>/g, '&gt;');
-
-  // Fenced code blocks: ```...```
-  html = html.replace(/(```[\s\S]*?```)/g, '<span class="ht-code-block">$1</span>');
-
-  // Inline code: `...`  (but not inside code blocks — already wrapped)
-  html = html.replace(/(?<!<span class="ht-code-block">[\s\S]*?)(`[^`\n]+?`)/g, '<span class="ht-inline-code">$1</span>');
-
-  // Bold: **...**
-  html = html.replace(/(\*\*[^*]+?\*\*)/g, '<span class="ht-bold">$1</span>');
-
-  // Italic: *...* (single, not inside bold)
-  html = html.replace(/(?<!\*)(\*[^*\n]+?\*)(?!\*)/g, '<span class="ht-italic">$1</span>');
-
-  // Headers at line start: # ...
-  html = html.replace(/(^|\n)(#{1,6}\s[^\n]*)/g, '$1<span class="ht-heading">$2</span>');
-
-  // Links: [text](url)
-  html = html.replace(/(\[[^\]]*\]\([^)]*\))/g, '<span class="ht-link">$1</span>');
-
-  // Ensure trailing newline for proper sizing
-  if (!html.endsWith('\n')) html += '\n';
-
-  return html;
-}
-
-export const HighlightedTextarea = forwardRef<HTMLTextAreaElement, Props>(
-  ({ value, highlightEnabled = true, className = '', ...props }, ref) => {
-    const textareaRef = useRef<HTMLTextAreaElement>(null);
-    const backdropRef = useRef<HTMLPreElement>(null);
-
-    useImperativeHandle(ref, () => textareaRef.current!);
-
-    // Sync scroll
-    const syncScroll = useCallback(() => {
-      if (textareaRef.current && backdropRef.current) {
-        backdropRef.current.scrollTop = textareaRef.current.scrollTop;
-        backdropRef.current.scrollLeft = textareaRef.current.scrollLeft;
-      }
-    }, []);
-
-    useEffect(() => {
-      syncScroll();
-    }, [value, syncScroll]);
-
-    if (!highlightEnabled) {
-      return (
-        <textarea
-          ref={textareaRef}
-          value={value}
-          className={className}
-          {...props}
-        />
-      );
-    }
-
-    return (
-      <div className="ht-container relative flex-1 min-w-0">
-        <pre
-          ref={backdropRef}
-          className={`ht-backdrop ${className}`}
-          aria-hidden="true"
-          dangerouslySetInnerHTML={{ __html: highlightMarkdown(value) }}
-        />
-        <textarea
-          ref={textareaRef}
-          value={value}
-          className={`ht-textarea ${className}`}
-          onScroll={syncScroll}
-          {...props}
-        />
-      </div>
-    );
-  }
-);
-
-HighlightedTextarea.displayName = 'HighlightedTextarea';

src/index.css

@@ -53,8 +53,6 @@
 }
 
 /* Chat textarea: no focus ring (container handles visual feedback) */
-.ht-textarea:focus-visible,
-.ht-textarea:focus,
 #chat-input:focus-visible,
 #chat-input:focus {
   outline: none;
@@ -202,77 +200,6 @@ html, body {
 .markdown-body th { background: var(--pc-accent-glow); }
 .markdown-body img { max-width: 100%; border-radius: 8px; }
 
-/* Highlighted textarea overlay */
-.ht-container {
-  position: relative;
-  flex: 1;
-  min-width: 0;
-  overflow: hidden;
-}
-
-.ht-backdrop,
-.ht-textarea {
-  /* Must share EXACTLY identical text layout — any difference causes cursor desync */
-  font-family: inherit;
-  font-size: inherit;
-  line-height: inherit;
-  letter-spacing: inherit;
-  word-spacing: inherit;
-  white-space: pre-wrap;
-  word-break: break-word;
-  overflow-wrap: break-word;
-  overflow-x: hidden;
-  overflow-y: auto;
-  margin: 0;
-  box-sizing: border-box;
-  /* padding, border, border-radius all come from the shared className */
-}
-
-.ht-backdrop {
-  position: absolute;
-  inset: 0;
-  pointer-events: none;
-  color: var(--pc-text-primary);
-  background: transparent;
-}
-
-.ht-textarea {
-  position: relative;
-  width: 100%;
-  color: transparent;
-  caret-color: var(--pc-text-primary);
-  background: transparent !important;
-  resize: none;
-  z-index: 1;
-}
-
-/* Token colors — ONLY color allowed, nothing that changes text geometry */
-.ht-code-block {
-  color: #67e8f9; /* cyan-300 */
-}
-
-.ht-inline-code {
-  color: #67e8f9;
-}
-
-.ht-bold {
-  color: var(--pc-text-primary);
-}
-
-.ht-italic {
-  color: var(--pc-text-secondary);
-  /* No font-style: italic — italic glyphs have different widths, causes cursor desync */
-}
-
-.ht-heading {
-  color: #a78bfa; /* violet-400 */
-  /* No font-weight — bolder glyphs are wider, causes cursor desync */
-}
-
-.ht-link {
-  color: #67e8f9;
-}
-
 /* Accessibility: respect reduced-motion preferences */
 @media (prefers-reduced-motion: reduce) {
   .animate-fade-in {