Need help with C++ syntax - repost

[Anonymous_Banned275]

@Chris-Kawa Thanbks , appreciate all of your help.
I have another issue - appears that my OS is broken again, so I need to keep this short.

What I actually want is to be able to reuse the project QMainWindow.

Obviously I cannot just instantiate it - there are other QMainWIndow in my subproject...

Can I build / add another class to the Terminal project and make MainWindow its member ?

[Chris Kawa]

QMainWindow is not a project. It's a class. You can have as many instances of it as you want:

QMainWindow* instance1 = new QMainWindow();
QMainWindow* instance2 = new QMainWindow();
...

If you mean you have multiple classes deriving QMainWindow just name them differently or put them in a namespace:

class SomeWindow: public QMainWindow
{
 ...
};

class SomeOtherWindow: public QMainWindow
{
 ...
};

SomeWindow* instance1 = new SomeWindow();
SomeOtherWindow* instance2 = new SomeOtherWindow();

or

namespace A
{
   class MainWindow: public QMainWindow
   {
    ...
   };
}

namespace B
{
   class MainWindow: public QMainWindow
   {
    ...
   };
}


A::MainWindow* instance1 = new A::MainWindow();
B::MainWindow* instance2 = new B::MainWindow();

[Anonymous_Banned275]

@Chris-Kawa Neat idea - so all I have to do is to rename the MainWindow in "Terminal" project...

[Anonymous_Banned275]

@AnneRanch Unfortunately little too complicated - I had to rename both .cpp and .h files....
Now it is failing when I use / reuse the original "MainNwindow" form - it has references to QMainWindow...
I'll try "namespace" next ....
However - I think the ideas to build a class - say "C_Terminal " and make the MainWindow its variable / method may work the best .... trying to make as little changes to the original "MainWindow" class...

[Anonymous_Banned275]

I need to "re group". I think I am making it more complicated then it needs to be

I think my last attempt to rename "MainWindow" was OK , but I missed the

"NAMESPACE" in header ....

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QSerialPort>

QT_BEGIN_NAMESPACE

class QLabel;

namespace Ui {
class MainWindow;
}

QT_END_NAMESPACE

class Console;
class SettingsDialog;

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private slots:
    void openSerialPort();
    void closeSerialPort();
    void about();
    void writeData(const QByteArray &data);
    void readData();

    void handleError(QSerialPort::SerialPortError error);

private:
    void initActionsConnections();

private:
    void showStatusMessage(const QString &message);

    Ui::MainWindow *m_ui = nullptr;
    QLabel *m_status = nullptr;
    Console *m_console = nullptr;
    SettingsDialog *m_settings = nullptr;
    QSerialPort *m_serial = nullptr;
};

#endif // MAINWINDOW_H

[Anonymous_Banned275]

@AnneRanch I am trying to understand how is "namespace " used in the "terminal " example.
Why is only "Ui" enclosed in "namespace"?

Or better yet - how do I "exited the namespace " to the entire class ?

[JoeCFD]

you see here:
Ui::MainWindow *m_ui = nullptr;
MainWindow belongs to namespace Ui. In order to use it, you have to define the class name first. It is the same as QLabel.

you have to define
class QLabel;
then you can use
QLabel *m_status = nullptr;
Otherwide QLabel is not defined.

MainWindow is defined in namespace. therefore you define it inside
namespace Ui {
class MainWindow;
}

this may save you a bit time. Same thing.

    Ui::MainWindow *m_ui{};
    QLabel *m_status{};
    Console *m_console{];
    SettingsDialog *m_settings{};
    QSerialPort *m_serial{};

[Anonymous_Banned275]

@JoeCFD ...but that defeats the (desired) task of reusing the existing code .

I went and added this piece of code

//QT_BEGIN_NAMESPACE TERMINAL_SERIAL

**namespace TERMINAL**
{
class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private slots:

Then I changed all references to MainWindow
to
TERMINAL::MainWindow

it complied and run BUT when I add TERMINAL
to the code / class which actually uses the TERMINAL namespace modified class I get an error

/media/nov25-1/MDI_BASE_RAID_5/DIRECT_BACKUP_DEC16_NAMESPACE/Qt-5.15.2/widgets/mainwindows/mdi/mainwindow.cpp:112: error: use of undeclared identifier 'TERMINAL'
mainwindow.cpp:112:9: error: use of undeclared identifier 'TERMINAL'
TERMINAL::MainWindow *MW = new MainWindow();
^

How do I make /mdi/mainwindow.cpp aware of "namespace TERMINAL" ?
Normal "include ' does not work ...

case 0:
{
qDebug() <<Q_FUNC_INFO; // "updateWindowMenu() build windows submenu ";
qDebug() << "& line " << QString::number(LINE);

    **TERMINAL::MainWindow *MW = new MainWindow();**  no go 


    mdiArea->addSubWindow(MW)->
            //         setWindowState(Qt::WindowMinimized) ;
            setWindowState(Qt::WindowMinimized) ;

[Chris Kawa]

@AnneRanch said:

Why is only "Ui" enclosed in "namespace"?

MainWindow is your class. Ui::MainWindow is another class, generated from the .ui file. It is put in the Ui namespace to denote that it is a designer generated class. It is instantiated in the constructor via new and assigned to the ui member variable. It holds pointers to all ui widgets and only has the setupUi method that sets your MainWindow with what you created in the designer.

As to renaming. Lets say you want to rename MainWindow to TerminalWindow.

1. Your MainWindow is a designer class, so it consists of 3 files: mainwindow.h, mainwindow.cpp and mainwindow.ui. Rename these to terminalwindow.h, terminalwindow.cpp and terminalwindow.ui.

2. In terminalwindow.h:

• rename class MainWindow : public QMainWindow to class TerminalWindow : public QMainWindow
• replace namespace Ui { class MainWindow; } with namespace Ui { class TerminalWindow; }
• replace Ui::MainWindow *ui; with Ui::TerminalWindow *ui;

3. In terminalwindow.cpp:

• change #include "mainwindow.h" to #include "terminalwindow.h"
• change #include "ui_mainwindow.h" to #include "ui_terminalwindow.h"
• change all methods from MainWindow::xxx to TerminalWindow::xxx
• change creation of the ui from ui(new Ui::MainWindow) to ui(new Ui::TerminalWindow)

4. In terminalwindow.ui you have 2 options:

• you can open it in the form designer, select MainWindow in the object hierarchy and change its objectName property from MainWindow to TerminalWindow
• or you can open it in a text editor and change the XML directly, replacing MainWindow with TerminalWindow

5. in all other files that use that class:

• change #include "mainwindow.h" to #include "terminalwindow.h"
• replace MainWindow with TerminalWindow

6. Last but not least, in your .pro file replace the names in SOURCES, HEADERS and FORMS from mainwindow.h, mainwindow.cpp and mainwindow.ui to terminalwindow.h, terminalwindow.cpp and terminalwindow.ui

[Anonymous_Banned275]

BUIDING PROGRESS

I hope this error is due to incomplete rebuidl, however , here itis in case it is not

/media/nov25-1/MDI_BASE_RAID_5/DIRECT_BACKUP_DEC15_C_TERMINAL_MAIN/Qt-5.15.2/serialport/terminal/terminal_mainwindow_copy.cpp:76: error: allocation of incomplete type 'Ui::Terminal_MainWindow'
terminal_mainwindow_copy.cpp:76:14: error: allocation of incomplete type 'Ui::Terminal_MainWindow'
    m_ui(new Ui::Terminal_MainWindow),
             ^~~~~~~~~~~~~~~~~~~~~~~
./terminal_mainwindow_copy.h:66:7: note: forward declaration of 'Ui::Terminal_MainWindow'
class Terminal_MainWindow;
      ^

this is the actual code posting the first error

//! [0]
Terminal_MainWindow::Terminal_MainWindow(QWidget *parent) :
    QMainWindow(parent),
    **m_ui(new Ui::Terminal_MainWindow),**    **source of error** 
    m_status(new QLabel),
    m_console(new Console),
    m_settings(new SettingsDialog),
//! [1]
    m_serial(new QSerialPort(this))
//! [1]
{
//! [0]
    qDebug() <<Q_FUNC_INFO; // "updateWindowMenu() build windows submenu  ";
    qDebug() << "& line " << QString::number(__LINE__);
    m_ui->setupUi(this);
    m_console->setEnabled(false);
    setCentralWidget(m_console);



    m_ui->actionConnect->setEnabled(true);


    m_ui->actionDisconnect->setEnabled(false);
    qDebug() <<Q_FUNC_INFO; // "updateWindowMenu() build windows submenu  ";
    qDebug() << "& line " << QString::number(__LINE__);
#ifdef BYPASS

Here is the snippet referring to "forward declaration " in error

QT_BEGIN_NAMESPACE

class QLabel;

namespace Ui {
//class MainWindow;
class Terminal_MainWindow;
// replace DONE
}

QT_END_NAMESPACE

class Console;
class SettingsDialog;

class Terminal_MainWindow : public QMainWindow
{
    Q_OBJECT

PS
I did use QT "duplicate file" and removed all the references to the original MainWindow

[Chris Kawa]

The definition of that symbol comes from the ui_terminal_mainwindow.h (or whatever you called it) file that gets generated form the .ui file, so either you didn't change the name in the .ui itself or it wasn't rebuilt. Make sure the change is there, delete your build directory (or just the generated ui_terminal_mainwindow.h) and rebuild. If in doubt you can just open that generated file and see if class Ui::Terminal_MainWindow is there or is it still Ui::MainWindow.

[Anonymous_Banned275]

OK, I did give it another try and still getting same error

/media/nov25-1/MDI_BASE_RAID_5/DIRECT_BACKUP_DEC17_TERMINAL/Qt-5.15.2/serialport/terminal/TERMINAL_mainwindow_copy.cpp:70: error: allocation of incomplete type 'Ui::TERMINAL_MainWindow'
TERMINAL_mainwindow_copy.cpp:70:14: error: allocation of incomplete type 'Ui::TERMINAL_MainWindow'
m_ui(new Ui::TERMINAL_MainWindow),
^~~~~~~~~~~~~~~~~~~~~~~
./TERMINAL_mainwindow_copy.h:63:7: note: forward declaration of 'Ui::TERMINAL_MainWindow'
class TERMINAL_MainWindow;
^

I am including full copies of .cpp and ,h files .

I DID Clean IT uP As much as i could, but keep in mind it is a code under construction
and it is being posted to help me find the error.

#ifndef TERMINAL_MAINWINDOW_COPY_H
#define TERMINAL_MAINWINDOW_COPY_H

#include <QMainWindow>
#include <QSerialPort>

QT_BEGIN_NAMESPACE

class QLabel;

namespace Ui {
class TERMINAL_MainWindow;
}

QT_END_NAMESPACE


class Console;
class SettingsDialog;


class TERMINAL_MainWindow : public QMainWindow
{
    Q_OBJECT

public:
#ifdef BYPASS
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
#endif
    explicit TERMINAL_MainWindow(QWidget *parent = nullptr);
    ~TERMINAL_MainWindow();

private slots:
    void openSerialPort(QT_END_NAMESPACE);
    void closeSerialPort();
    void about();
    void writeData(const QByteArray &data);
    void readData();

    void handleError(QSerialPort::SerialPortError error);

private:
    void initActionsConnections();

private:
    void showStatusMessage(const QString &message);

    Ui::TERMINAL_MainWindow *m_ui; //  = nullptr;
    QLabel *m_status = nullptr;
    Console *m_console = nullptr;
    SettingsDialog *m_settings = nullptr;
    QSerialPort *m_serial = nullptr;
};


#endif // TERMINAL_MAINWINDOW_COPY_H

//#include "mainwindow.h"
#include "TERMINAL_mainwindow_copy.h"
// DONE

//#include "ui_mainwindow.h"
//  change #include "ui_mainwindow.h" to #include "ui_terminalwindow.h"
#include "ui_TERMINAL_mainwindow_copy.h"
// this was missing

#include "console.h"
#include "settingsdialog.h"

#include <QLabel>
#include <QMessageBox>
//  change creation of the ui from ui(new Ui::MainWindow) to ui(new Ui::TerminalWindow)
//! [0]
TERMINAL_MainWindow::TERMINAL_MainWindow(QWidget *parent) :
    QMainWindow(parent),
    m_ui(new Ui::TERMINAL_MainWindow),
    m_status(new QLabel),
    m_console(new Console),
    m_settings(new SettingsDialog),
//! [1]
    m_serial(new QSerialPort(this))
//! [1]
{
//! [0]
    m_ui->setupUi(this);
    m_console->setEnabled(false);
    setCentralWidget(m_console);

    m_ui->actionConnect->setEnabled(true);
    m_ui->actionDisconnect->setEnabled(false);
    m_ui->actionQuit->setEnabled(true);
    m_ui->actionConfigure->setEnabled(true);

    m_ui->statusBar->addWidget(m_status);

    initActionsConnections();

    connect(m_serial, &QSerialPort::errorOccurred, this, &TERMINAL_MainWindow::handleError);

//! [2]
    connect(m_serial, &QSerialPort::readyRead, this, &TERMINAL_MainWindow::readData);
//! [2]
    connect(m_console, &Console::getData, this, &TERMINAL_MainWindow::writeData);
//! [3]
}
//! [3]

TERMINAL_MainWindow::~TERMINAL_MainWindow()
{
    delete m_settings;
    delete m_ui;
}

//! [4]
void TERMINAL_MainWindow::openSerialPort()
{
    const SettingsDialog::Settings p = m_settings->settings();
    m_serial->setPortName(p.name);
    m_serial->setBaudRate(p.baudRate);
    m_serial->setDataBits(p.dataBits);
    m_serial->setParity(p.parity);
    m_serial->setStopBits(p.stopBits);
    m_serial->setFlowControl(p.flowControl);
    if (m_serial->open(QIODevice::ReadWrite)) {
        m_console->setEnabled(true);
        m_console->setLocalEchoEnabled(p.localEchoEnabled);
        m_ui->actionConnect->setEnabled(false);
        m_ui->actionDisconnect->setEnabled(true);
        m_ui->actionConfigure->setEnabled(false);
        showStatusMessage(tr("Connected to %1 : %2, %3, %4, %5, %6")
                          .arg(p.name).arg(p.stringBaudRate).arg(p.stringDataBits)
                          .arg(p.stringParity).arg(p.stringStopBits).arg(p.stringFlowControl));
    } else {
        QMessageBox::critical(this, tr("Error"), m_serial->errorString());

        showStatusMessage(tr("Open error"));
    }
}
//! [4]

//! [5]
void TERMINAL_MainWindow::closeSerialPort()
{
    if (m_serial->isOpen())
        m_serial->close();
    m_console->setEnabled(false);
    m_ui->actionConnect->setEnabled(true);
    m_ui->actionDisconnect->setEnabled(false);
    m_ui->actionConfigure->setEnabled(true);
    showStatusMessage(tr("Disconnected"));
}
//! [5]

void TERMINAL_MainWindow::about()
{
    QMessageBox::about(this, tr("About Simple Terminal"),
                       tr("The <b>Simple Terminal</b> example demonstrates how to "
                          "use the Qt Serial Port module in modern GUI applications "
                          "using Qt, with a menu bar, toolbars, and a status bar."));
}

//! [6]
void TERMINAL_MainWindow::writeData(const QByteArray &data)
{
    m_serial->write(data);
}
//! [6]

//! [7]
void TERMINAL_MainWindow::readData()
{
    const QByteArray data = m_serial->readAll();
    m_console->putData(data);
}
//! [7]

//! [8]
void TERMINAL_MainWindow::handleError(QSerialPort::SerialPortError error)
{
    if (error == QSerialPort::ResourceError) {
        QMessageBox::critical(this, tr("Critical Error"), m_serial->errorString());
        closeSerialPort();
    }
}
//! [8]

void TERMINAL_MainWindow::initActionsConnections()
{
    connect(m_ui->actionConnect, &QAction::triggered, this, &TERMINAL_MainWindow::openSerialPort);
    connect(m_ui->actionDisconnect, &QAction::triggered, this, &TERMINAL_MainWindow::closeSerialPort);
    connect(m_ui->actionQuit, &QAction::triggered, this, &TERMINAL_MainWindow::close);
    connect(m_ui->actionConfigure, &QAction::triggered, m_settings, &SettingsDialog::show);
    connect(m_ui->actionClear, &QAction::triggered, m_console, &Console::clear);
    connect(m_ui->actionAbout, &QAction::triggered, this, &TERMINAL_MainWindow::about);
    connect(m_ui->actionAboutQt, &QAction::triggered, qApp, &QApplication::aboutQt);
}

void TERMINAL_MainWindow::showStatusMessage(const QString &message)
{
    m_status->setText(message);
}

[Chris Kawa]

Like I said - open that generated ui_TERMINAL_mainwindow_copy.h and see what class name is there. There should be a class Ui_TERMINAL_MainWindow and below it, in a namespace Ui class TERMINAL_MainWindow : public Ui_TERMINAL_MainWindow.
If any of those is still just MainWindow then you haven't done the renaming in the .ui file (maybe a typo, wrong place or anything like that).

[Anonymous_Banned275]

@Chris-Kawa said in Need help with C++ syntax - repost:

Like I said - open that generated ui_TERMINAL_mainwindow_copy.h and see what class name is there. There should be a class Ui_TERMINAL_MainWindow and below it, in a namespace Ui class TERMINAL_MainWindow : public Ui_TERMINAL_MainWindow.
If any of those is still just MainWindow then you haven't done the renaming in the .ui file (maybe a typo, wrong place or anything like that).

caorrect - this is the problem

/********************************************************************************
** Form generated from reading UI file 'TERMINAL_mainwindow_copy.ui'
**
** Created by: Qt User Interface Compiler version 5.15.2
**
** WARNING! All changes made in this file will be lost when recompiling UI file!
********************************************************************************/

#ifndef UI_TERMINAL_MAINWINDOW_COPY_H
#define UI_TERMINAL_MAINWINDOW_COPY_H

#include <QtCore/QVariant>
#include <QtWidgets/QAction>
#include <QtWidgets/QApplication>
#include <QtWidgets/QMainWindow>
#include <QtWidgets/QMenu>
#include <QtWidgets/QMenuBar>
#include <QtWidgets/QStatusBar>
#include <QtWidgets/QToolBar>
#include <QtWidgets/QVBoxLayout>
#include <QtWidgets/QWidget>

QT_BEGIN_NAMESPACE

class Ui_MainWindow
{
public:
    QAction *actionAbout;
    QAction *actionAboutQt;
    QAction *actionConnect;
    QAction *actionDisconnect;
    QAction *actionConfigure;
    QAction *actionClear;
    QAction *actionQuit;
    QWidget *centralWidget;
    QVBoxLayout *verticalLayout;
    QMenuBar *menuBar;
    QMenu *menuCalls;
    QMenu *menuTools;
    QMenu *menuHelp;
    QToolBar *mainToolBar;
    QStatusBar *statusBar;

    void setupUi(QMainWindow *MainWindow)
    {
        if (MainWindow->objectName().isEmpty())
            MainWindow->setObjectName(QString::fromUtf8("MainWindow"));
        MainWindow->resize(400, 300);
        actionAbout = new QAction(MainWindow);
        actionAbout->setObjectName(QString::fromUtf8("actionAbout"));
        actionAboutQt = new QAction(MainWindow);
        actionAboutQt->setObjectName(QString::fromUtf8("actionAboutQt"));
        actionConnect = new QAction(MainWindow);
        actionConnect->setObjectName(QString::fromUtf8("actionConnect"));
        QIcon icon;
        icon.addFile(QString::fromUtf8(":/images/connect.png"), QSize(), QIcon::Normal, QIcon::Off);
        actionConnect->setIcon(icon);
        actionDisconnect = new QAction(MainWindow);
        actionDisconnect->setObjectName(QString::fromUtf8("actionDisconnect"));
        QIcon icon1;
        icon1.addFile(QString::fromUtf8(":/images/disconnect.png"), QSize(), QIcon::Normal, QIcon::Off);
        actionDisconnect->setIcon(icon1);
        actionConfigure = new QAction(MainWindow);
        actionConfigure->setObjectName(QString::fromUtf8("actionConfigure"));
        QIcon icon2;
        icon2.addFile(QString::fromUtf8(":/images/settings.png"), QSize(), QIcon::Normal, QIcon::Off);
        actionConfigure->setIcon(icon2);
        actionClear = new QAction(MainWindow);
        actionClear->setObjectName(QString::fromUtf8("actionClear"));
        QIcon icon3;
        icon3.addFile(QString::fromUtf8(":/images/clear.png"), QSize(), QIcon::Normal, QIcon::Off);
        actionClear->setIcon(icon3);
        actionQuit = new QAction(MainWindow);
        actionQuit->setObjectName(QString::fromUtf8("actionQuit"));
        QIcon icon4;
        icon4.addFile(QString::fromUtf8(":/images/application-exit.png"), QSize(), QIcon::Normal, QIcon::Off);
        actionQuit->setIcon(icon4);
        centralWidget = new QWidget(MainWindow);
        centralWidget->setObjectName(QString::fromUtf8("centralWidget"));
        verticalLayout = new QVBoxLayout(centralWidget);
        verticalLayout->setSpacing(6);
        verticalLayout->setContentsMargins(11, 11, 11, 11);
        verticalLayout->setObjectName(QString::fromUtf8("verticalLayout"));
        MainWindow->setCentralWidget(centralWidget);
        menuBar = new QMenuBar(MainWindow);
        menuBar->setObjectName(QString::fromUtf8("menuBar"));
        menuBar->setGeometry(QRect(0, 0, 400, 19));
        menuCalls = new QMenu(menuBar);
        menuCalls->setObjectName(QString::fromUtf8("menuCalls"));
        menuTools = new QMenu(menuBar);
        menuTools->setObjectName(QString::fromUtf8("menuTools"));
        menuHelp = new QMenu(menuBar);
        menuHelp->setObjectName(QString::fromUtf8("menuHelp"));
        MainWindow->setMenuBar(menuBar);
        mainToolBar = new QToolBar(MainWindow);
        mainToolBar->setObjectName(QString::fromUtf8("mainToolBar"));
        MainWindow->addToolBar(Qt::TopToolBarArea, mainToolBar);
        statusBar = new QStatusBar(MainWindow);
        statusBar->setObjectName(QString::fromUtf8("statusBar"));
        MainWindow->setStatusBar(statusBar);

        menuBar->addAction(menuCalls->menuAction());
        menuBar->addAction(menuTools->menuAction());
        menuBar->addAction(menuHelp->menuAction());
        menuCalls->addAction(actionConnect);
        menuCalls->addAction(actionDisconnect);
        menuCalls->addSeparator();
        menuCalls->addAction(actionQuit);
        menuTools->addAction(actionConfigure);
        menuTools->addAction(actionClear);
        menuHelp->addAction(actionAbout);
        menuHelp->addAction(actionAboutQt);
        mainToolBar->addAction(actionConnect);
        mainToolBar->addAction(actionDisconnect);
        mainToolBar->addAction(actionConfigure);
        mainToolBar->addAction(actionClear);

        retranslateUi(MainWindow);

        QMetaObject::connectSlotsByName(MainWindow);
    } // setupUi

    void retranslateUi(QMainWindow *MainWindow)
    {
        MainWindow->setWindowTitle(QCoreApplication::translate("MainWindow", "Simple Terminal", nullptr));
        actionAbout->setText(QCoreApplication::translate("MainWindow", "&About", nullptr));
#if QT_CONFIG(tooltip)
        actionAbout->setToolTip(QCoreApplication::translate("MainWindow", "About program", nullptr));
#endif // QT_CONFIG(tooltip)
#if QT_CONFIG(shortcut)
        actionAbout->setShortcut(QCoreApplication::translate("MainWindow", "Alt+A", nullptr));
#endif // QT_CONFIG(shortcut)
        actionAboutQt->setText(QCoreApplication::translate("MainWindow", "About Qt", nullptr));
        actionConnect->setText(QCoreApplication::translate("MainWindow", "C&onnect", nullptr));
#if QT_CONFIG(tooltip)
        actionConnect->setToolTip(QCoreApplication::translate("MainWindow", "Connect to serial port", nullptr));
#endif // QT_CONFIG(tooltip)
#if QT_CONFIG(shortcut)
        actionConnect->setShortcut(QCoreApplication::translate("MainWindow", "Ctrl+O", nullptr));
#endif // QT_CONFIG(shortcut)
        actionDisconnect->setText(QCoreApplication::translate("MainWindow", "&Disconnect", nullptr));
#if QT_CONFIG(tooltip)
        actionDisconnect->setToolTip(QCoreApplication::translate("MainWindow", "Disconnect from serial port", nullptr));
#endif // QT_CONFIG(tooltip)
#if QT_CONFIG(shortcut)
        actionDisconnect->setShortcut(QCoreApplication::translate("MainWindow", "Ctrl+D", nullptr));
#endif // QT_CONFIG(shortcut)
        actionConfigure->setText(QCoreApplication::translate("MainWindow", "&Configure", nullptr));
#if QT_CONFIG(tooltip)
        actionConfigure->setToolTip(QCoreApplication::translate("MainWindow", "Configure serial port", nullptr));
#endif // QT_CONFIG(tooltip)
#if QT_CONFIG(shortcut)
        actionConfigure->setShortcut(QCoreApplication::translate("MainWindow", "Alt+C", nullptr));
#endif // QT_CONFIG(shortcut)
        actionClear->setText(QCoreApplication::translate("MainWindow", "C&lear", nullptr));
#if QT_CONFIG(tooltip)
        actionClear->setToolTip(QCoreApplication::translate("MainWindow", "Clear data", nullptr));
#endif // QT_CONFIG(tooltip)
#if QT_CONFIG(shortcut)
        actionClear->setShortcut(QCoreApplication::translate("MainWindow", "Alt+L", nullptr));
#endif // QT_CONFIG(shortcut)
        actionQuit->setText(QCoreApplication::translate("MainWindow", "&Quit", nullptr));
#if QT_CONFIG(shortcut)
        actionQuit->setShortcut(QCoreApplication::translate("MainWindow", "Ctrl+Q", nullptr));
#endif // QT_CONFIG(shortcut)
        menuCalls->setTitle(QCoreApplication::translate("MainWindow", "Calls", nullptr));
        menuTools->setTitle(QCoreApplication::translate("MainWindow", "Tools", nullptr));
        menuHelp->setTitle(QCoreApplication::translate("MainWindow", "Help", nullptr));
    } // retranslateUi

};

namespace Ui {
    class MainWindow: public Ui_MainWindow {};
} // namespace Ui

QT_END_NAMESPACE

#endif // UI_TERMINAL_MAINWINDOW_COPY_H

/********************************************************************************
** Form generated from reading UI file 'TERMINAL_mainwindow_copy.ui'
**
** Created by: Qt User Interface Compiler version 5.15.2
**
** WARNING! All changes made in this file will be lost when recompiling UI file!
********************************************************************************/

Here is the issue - I have NEVER grasped the relations between .ui file and UI files .

Here is the directory structure and the "form" has been renamed .

The (form) . ui has be renamed and the CREATED ui file still has the original class name ....

So - where is the missing link /m source of error ?

PS
here is my terminal.pro

QT += widgets serialport
requires(qtConfig(combobox))

TARGET = terminal
#TEMPLATE = app
TEMPLATE = lib
SOURCES += \
    TERMINAL_mainwindow_copy.cpp \
    class_terminal.cpp \
    main.cpp \
#    mainwindow.cpp \
    settingsdialog.cpp \
    console.cpp

HEADERS += \
    TERMINAL_NOTES.h \
    TERMINAL_mainwindow_copy.h \
    class_terminal.h \
#    mainwindow.h \
    settingsdialog.h \
    console.h

FORMS += \
    TERMINAL_mainwindow_copy.ui \
 #   mainwindow.ui \
    settingsdialog.ui

RESOURCES += \
    terminal.qrc

target.path = $$[QT_INSTALL_EXAMPLES]/serialport/terminal
INSTALLS += target

[Anonymous_Banned275]

PROGRESS (?) REPORT
I have removed all the contents of the "generated" Ui_ file.
After "rebuild" of the entire project - it fails same way .

The "rebuild" file still DOES NOT reflect the renaming of the header file.

I can try to find the ui_ file and actually delete it....

or

it looks there is something else missing in rebuilding the renamed header.

[Anonymous_Banned275]

SUCCESS SOLVED CASE CLOSED (?)

The moral of the story

changing the name of the header file has no effect in changing the object name in the "form"

Thanks to all for much needed assistance , especially Chis.