QTextEdit change Fontsize after using QTextCharFormat

Hi all,

after calling QTextCharFormat to set specific words' font size,

i cannot update the whole text's font anymore.

For example:

I have an idea.

"an idea" is changed by the function below:

Code:

---

void testTextView :: setInsertTextFont(const QFont& font)
{
   QTextCharFormat fmt;
   fmt.setFont(font);
 
   QTextCursor cursor = m_edit -> textCursor();
   cursor.mergeCharFormat(fmt);
 
   m_edit -> mergeCurrentCharFormat(fmt);
}

---

then when I called QTextEdit::setFont() and zoomIn()/zoomOut(), only "I have" change to the size I wanted,
but "an idea" remains the same state as before.

any idea to fix the problem?