Text caret invisible on position:relative elements (Firefox)

현상

In Firefox on Windows, when editing content inside an element with position:relative, the text caret is completely invisible.

재현 예시

1. Create a container element with position:relative.
2. Place contenteditable element inside it.
3. Focus on the contenteditable element.
4. ❌ Caret is not visible!

관찰된 동작

• No visible caret: Cannot see where text will be inserted
• Text still appears: Typed text shows up in editor
• Difficult editing: User has to guess insertion point
• Affects multiple browsers: Confirmed on Firefox, Safari, Chrome on macOS

예상 동작

• Caret should be visible (blinking line or other indicator)
• User should clearly see insertion point
• position:relative should not affect caret rendering

참고사항 및 가능한 해결 방향

• Remove position:relative: Remove the problematic CSS property from parent
• Use position:static: Change to static positioning
• Move to wrapper element: Apply position:relative to wrapper, keep editor static
• Custom caret implementation: Create blinking cursor with CSS animation

코드 예시

Solution 1: Remove position:relative

.editable-container {
  position: static; /* Remove or omit position property */
}

[contenteditable] {
  min-height: 100px;
  outline: 2px solid #ddd;
}

Solution 2: Wrapper element

.wrapper {
  position: relative;
  padding: 20px;
  border: 1px solid #ccc;
}

[contenteditable] {
  position: static; /* Keep contenteditable static */
  min-height: 100px;
}

Solution 3: Custom caret

@keyframes caret-blink {
  0%, 100% { opacity: 1; }
  50% { opacity: 0; }
}

.custom-caret {
  position: absolute;
  width: 2px;
  height: 20px;
  background: black;
  animation: caret-blink 1s infinite;
  pointer-events: none;
}

const editor = document.querySelector('[contenteditable]');
const caret = document.createElement('span');
caret.className = 'custom-caret';
document.body.appendChild(caret);

editor.addEventListener('input', (e) => {
  const selection = window.getSelection();
  if (selection.rangeCount > 0) {
    const range = selection.getRangeAt(0);
    const rect = range.getBoundingClientRect();
    
    // Update caret position
    caret.style.top = rect.top + 'px';
    caret.style.left = rect.left + 'px';
  }
});