Ugly tabs on macOS

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QTabWidget>


namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private:
    Ui::MainWindow *ui;

    QTabWidget *tabs;
};

#endif // MAINWINDOW_H

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QPlainTextEdit>

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

    tabs = new QTabWidget(this);
    setCentralWidget(tabs);

    tabs->setDocumentMode(true);

    for (auto i = 0; i < 3; ++i) {
        auto editor = new QPlainTextEdit();
        tabs->addTab(editor, "Editor");
    }
}

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