Reaching the information of mainwindow from a class

Hi there

I have a code which makes a simple paint which let the user draw Line, Rectangle, Ellipse ... , and works well, but what I did is to put all the information of different shapes in MainWindow.cpp.
Now I want to edit this code and make a class for each shape, but I donnow how to reach the informaion in MainWindow.cpp from classes.

I tried I thought of making a line class, in the header folder I make no change, but in the .cpp file, I put #include "mainwindow.h", so I suppose information from initUi should be available from my new class, I moved codes related to line action to new class and tried it. But as errors show, including mainwindow as a header file, seems it's not possible to reach to initUi.

I was advised to use SIGNAL/SLOT for this aim, but I really donnow how.

Is there anyone who can help me about making a different class just for Line action?

The code consists of: MainWindow.h & .cpp / paintscene.h & .cpp / drawhistory.h & .cpp

I include MainWindow.cpp, as I believe it's only thing needed and related, but if you want I can include other files too.
I attach a photo of result too.

Code:

#include "mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    this->initUi();
    this->loadSettings();
}
 
MainWindow::~MainWindow()
{
    this->saveSettings();
}
 
void MainWindow::initUi()
{
    this->setCentralWidget(new QWidget(this));
 
    this->setMenuBar(new QMenuBar(this->centralWidget()));
 
    auto toolBar = new QToolBar(this->centralWidget());
    this->addToolBar(toolBar);
 
    this->setStatusBar(new QStatusBar(this->centralWidget()));
 
    _paintScene = new PaintScene(this);
 
    auto *layout = new QVBoxLayout(this->centralWidget());
 
    layout->addWidget(_paintScene);
 
    auto figMenu = this->menuBar()->addMenu(tr("Figures"));
    auto aboutMenu = this->menuBar()->addMenu(tr("About"));
 
    //figures
    auto lineAction = figMenu->addAction(QIcon(":/img/Resources/Img/line_stroked"), tr("Draw line"));
    auto rectAction = figMenu->addAction(QIcon(":/img/Resources/Img/rectangle_stroked"), tr("Draw rect"));
    auto ellipseAction = figMenu->addAction(QIcon(":/img/Resources/Img/ellipse_stroked"), tr("Draw ellipse"));
    auto polyAction = figMenu->addAction(QIcon(":/img/Resources/Img/polyline"), tr("Draw polyline"));
    auto brushAction = figMenu->addAction(QIcon(":/img/Resources/Img/paint_brush"), tr("Free draw"));
    figMenu->addSeparator();
    auto undoAction = figMenu->addAction(QIcon(":/img/Resources/Img/undo"), tr("Undo"));
 
    //about
    auto aboutAction = aboutMenu->addAction(tr("About"));
 
    lineAction->setCheckable	(true);
    rectAction->setCheckable	(true);
    ellipseAction->setCheckable	(true);
    polyAction->setCheckable	(true);
    brushAction->setCheckable	(true);
 
    auto figGroup = new QActionGroup(figMenu);
    figGroup->addAction(lineAction);
    figGroup->addAction(rectAction);
    figGroup->addAction(ellipseAction);
    figGroup->addAction(polyAction);
    figGroup->addAction(brushAction);
 
    //shortcuts
    lineAction->setShortcut		(Qt::CTRL + Qt::Key_L);
    rectAction->setShortcut		(Qt::CTRL + Qt::Key_R);
    ellipseAction->setShortcut	(Qt::CTRL + Qt::Key_E);
    polyAction->setShortcut		(Qt::CTRL + Qt::Key_M);
    brushAction->setShortcut	(Qt::CTRL + Qt::Key_B);
    undoAction->setShortcut		(Qt::CTRL + Qt::Key_Z);
 
    //status tips
    lineAction->setStatusTip	(tr("Draw line (Ctrl + L)"));
    rectAction->setStatusTip	(tr("Draw rectangle (Ctrl + R)"));
    ellipseAction->setStatusTip	(tr("Draw ellipse (Ctrl + E)"));
    polyAction->setStatusTip	(tr("Draw polyline (Ctrl + M)"));
    brushAction->setStatusTip	(tr("Free draw (Ctrl + B)"));
    undoAction->setStatusTip	(tr("Undo last action (Ctrl + Z)"));
    aboutAction->setStatusTip	(tr("About this program"));
 
    //tool tips
    lineAction->setToolTip		(tr("Draw line (Ctrl + L)"));
    rectAction->setToolTip		(tr("Draw rectangle (Ctrl + R)"));
    ellipseAction->setToolTip	(tr("Draw ellipse (Ctrl + E)"));
    polyAction->setToolTip		(tr("Draw polyline (Ctrl + P)"));
    brushAction->setToolTip		(tr("Free draw (Ctrl + B)"));
    undoAction->setToolTip		(tr("Undo last action (Ctrl + Z)"));
 
    //add actions to tool bar
    toolBar->addActions(figGroup->actions());
    toolBar->addSeparator();
    toolBar->addAction(undoAction);
 
    //add functions to actions
    //figures
    connect(lineAction, &QAction::triggered, [&](bool checked) mutable {
        if(checked)
            _paintScene->setTool(PaintScene::Tools::line);
    });
    connect(rectAction, &QAction::triggered, [&](bool checked) mutable {
        if(checked)
            _paintScene->setTool(PaintScene::Tools::rect);
    });
    connect(ellipseAction, &QAction::triggered, [&](bool checked) mutable {
        if(checked)
            _paintScene->setTool(PaintScene::Tools::ellipse);
    });
    connect(polyAction, &QAction::triggered, [&](bool checked) mutable {
        if(checked)
            _paintScene->setTool(PaintScene::Tools::poly);
    });
    connect(brushAction, &QAction::triggered, [&](bool checked) mutable {
        if(checked)
            _paintScene->setTool(PaintScene::Tools::brush);
    });
 
    lineAction->setChecked(true);
    //for shure
    _paintScene->setTool(PaintScene::Tools::line);
 
    //undo
    connect(undoAction, &QAction::triggered, [&]() mutable {
        _paintScene->undo();
    });
 
    connect(aboutAction, &QAction::triggered, [&](){
        auto w = new QWidget(this, Qt::Window);
        w->setWindowModality(Qt::WindowModal);
        w->setWindowIcon(this->windowIcon());
        w->setWindowTitle(tr("About"));
 
        auto *lay = new QVBoxLayout(w);
 
        auto image = new QLabel(w);
        image->setPixmap(QPixmap(":/img/qt"));
 
        lay->addWidget(new QLabel(tr("Made with Qt 5.7"), w), 0, Qt::AlignHCenter);
        lay->addWidget(image);
 
        w->show();
    });
}
 
 
void MainWindow::saveSettings()
{
    QSettings s(QCoreApplication::applicationDirPath() + "/config.ini", QSettings::IniFormat);
 
    s.beginGroup("window");
    s.setValue("geometry", this->geometry());
    s.endGroup();
 
    s.sync();
}
 
 
void MainWindow::loadSettings()
{
    QSettings s(QCoreApplication::applicationDirPath() + "/config.ini", QSettings::IniFormat);
 
    s.beginGroup("window");
    this->setGeometry(s.value("geometry", QRect(100, 100, 500, 500)).toRect());
    s.endGroup();
}