QT-qtextedit how to set part of the text read-only (partially editable)

Overview

I've been writing a file system recently.
The infrastructure has been written for a while, and it's basically the same. Also need to use QT to do a shell interactive program interface. Refer to the shells of mac, linux and windows, all of which are operated in a text box. And
in
this text, only the bottom line can be entered. The problem is:

---

How to set part of the text read-only in qtextedit?

Ideas:

Follow us: Cursor! If the position of the cursor changes (not the bottom line), then set the text to read-only (setReadOnly(true)); otherwise (setReadOnly(false));
the following key is how to track it?

Use the signal-slot mechanism.

connect( myTextEdit, SIGNAL(cursorPositionChanged()), SLOT(on_textEdit_cursorPositionChanged()) );

The cursorPositionChanged() system here already exists. And
on_textEdit_cursorPositionChanged()
needs to be written by itself:
write the function under widget:

void Widget::on_textEdit_cursorPositionChanged()
{
  //当前光标
    qDebug()<<"coming"<<endl;           //可以看到行号随着光标的改变而改变

  QTextCursor tc = myTextEdit->textCursor();
  QTextLayout *pLayout = tc.block().layout();
  //当前光标在本BLOCK内的相对位置
  int nCurpos = tc.position() - tc.block().position();
  int nTextline = pLayout->lineForTextPosition(nCurpos).lineNumber() + tc.block().firstLineNumber();
  qDebug()<<nTextline<<endl;           //可以看到行号随着光标的改变而改变
}

and documented in the header file.

It should also be noted that a lot of people have reported slot loss errors:

Object::connect: No such slot （QT槽丢失问题）

This is because your slot function is not placed under it

private slot:

The complete code is given below:

code

main.cpp

#include "widget.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.resize(300,300);
    w.show();

    return a.exec();
}

widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QTextEdit>

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = 0);
private:
    QTextEdit *myTextEdit;
    int max_line;
private slots:
    void on_textEdit_cursorPositionChanged();
};

#endif

widget.cpp

#include "widget.h"
#include <QTextLayout>
#include <QTextBlock>
#include <QDebug>
void Widget::on_textEdit_cursorPositionChanged()
{
  //当前光标
    qDebug()<<"coming"<<endl;           //可以看到行号随着光标的改变而改变

  QTextCursor tc = myTextEdit->textCursor();
  QTextLayout *pLayout = tc.block().layout();
  //当前光标在本BLOCK内的相对位置
  int nCurpos = tc.position() - tc.block().position();
  int nTextline = pLayout->lineForTextPosition(nCurpos).lineNumber() + tc.block().firstLineNumber();
  qDebug()<<nTextline<<endl;           //可以看到行号随着光标的改变而改变
}

Widget::Widget(QWidget *parent) :
    QWidget(parent)
{
    setWindowTitle(tr("Viverrine-guest"));
    myTextEdit = new QTextEdit(this);
    myTextEdit->setFocus();               //得到鼠標
    myTextEdit->setText(tr("這是一段text內容：\n內容通常很多......"));  //設定內容文字
    myTextEdit->setGeometry(0,0,550,330); //設定位置大小
    qDebug()<<"nTextline"<<endl;           //可以看到行号随着光标的改变而改变
    connect( myTextEdit, SIGNAL(cursorPositionChanged()), SLOT(on_textEdit_cursorPositionChanged()) );

}

You can see the number of lines printed. Here read-only and writable can be written in additionally.