Textedit - can't reset charFormat after highlight

[ChrisW67]

I generated a basic QMainWindow project with aQTextEdit as the central widget. This code caches the formats and generates a stream of foreign text that switches from plain to highlighted and back without issue. run it an type continously for a few seconds. Useful?

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
#include <QTimer>
 
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
    , m_timer(nullptr)
{
    ui->setupUi(this);
 
    m_base = ui->textEdit->textCursor().charFormat();
    m_highlighted = m_base;
    m_highlighted.setBackground(Qt::yellow);
 
    m_timer = new QTimer(this);
    connect(m_timer, &QTimer::timeout, this, &MainWindow::writeForeignText);
    m_timer->setInterval(5000);
    m_timer->start();
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::writeForeignText()
{
    QTextCursor cursor = ui->textEdit->textCursor();
    cursor.setCharFormat(m_highlighted);
    cursor.insertText("Plugh");
    cursor.setCharFormat(m_base);
    ui->textEdit->setTextCursor(cursor);
}

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QTimer>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
    , m_timer(nullptr)
{
    ui->setupUi(this);

    m_base = ui->textEdit->textCursor().charFormat();
    m_highlighted = m_base;
    m_highlighted.setBackground(Qt::yellow);

    m_timer = new QTimer(this);
    connect(m_timer, &QTimer::timeout, this, &MainWindow::writeForeignText);
    m_timer->setInterval(5000);
    m_timer->start();
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::writeForeignText()
{
    QTextCursor cursor = ui->textEdit->textCursor();
    cursor.setCharFormat(m_highlighted);
    cursor.insertText("Plugh");
    cursor.setCharFormat(m_base);
    ui->textEdit->setTextCursor(cursor);
}

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