QTextEdit. How to select text manually?

I encountered a similar problem. In Windows 10, there might be a bug of 'drag/move'. We use QT_NO_DRAGANDDROP as a compiler option, which makes text selection in QTextEdit not work anymore.

Solution:

void QTextEditEx::mouseMoveEvent(QMouseEvent *event)
{
    QTextEdit::mouseMoveEvent(event);
    if (event->buttons() & Qt::LeftButton)
    {
        QTextCursor cursor = textCursor();
        QTextCursor endCursor = cursorForPosition(event->pos()); // key point
        cursor.setPosition(pos, QTextCursor::MoveAnchor);
        cursor.setPosition(endCursor.position(), QTextCursor::KeepAnchor);
        setTextCursor(cursor);
    }
}

void QTextEditEx::mousePressEvent(QMouseEvent *event)
{
    QTextEdit::mousePressEvent(event);
    if (event->buttons() & Qt::LeftButton)
    {
        QTextCursor cursor = cursorForPosition(event->pos());
        // int pos; member variable
        pos = cursor.position();
        cursor.clearSelection();
        setTextCursor(cursor);
    }
}

reference:

1. Two existing answers

2. QTextEdit: get word under the mouse pointer?

 QTextCursor c = textEdit->textCursor();
 c.setPosition(startPos);
 c.setPosition(endPos, QTextCursor::KeepAnchor);
 textEdit->setTextCursor(c);

This piece of code moves the cursor to the start position of the selection using setPosition, then moves it to the end of the selection, but leaves the selection anchor at the old position by specifying a MoveMode as the second parameter.

The last line sets the selection to be visible inside the edit control, so you should skip it if you just want to do some manipulations with the selected text.

Also, if you don't have the exact positions, movePosition is helpful: you can move the cursor in various ways, such as one word to the right or down one line.