Custom QWidget (Qwt) class not found when promoted

Kevin470

I have a QWidget element on my ui which I would like to use for as a plotter.
I am trying to promote it to a custom class (MyPlot) of mine which inherits QwtPlot.

The Qwt package is found and CMake runs fine. But when I try to build it, the ui_mainwindow.h file is not finding my custom class.

It throws the error : ui_mainwindow.h:19:10: 'src/myplot.hpp' file not found

My CMakeLists.txt file looks like this:

cmake_minimum_required(VERSION 3.5)

project(Front VERSION 0.1 LANGUAGES CXX)

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)

set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "cmake")

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

# extend cmake module path find additional .cmake module (here in Qwt)
set(CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake")

find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Widgets)
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Widgets)

# prepare QWT library
set (QWT_LIBRARY "c:/cpp_libs/Qwt/Qwt-6.2.0/lib")
set (QWT_INCLUDE_DIR "c:/cpp_libs/Qwt/Qwt-6.2.0/include")
find_package(Qwt)

if(Qwt_FOUND)
    message(STATUS "QWT Package Found")
endif()

set(PROJECT_SOURCES
        src/main.cpp
        src/mainwindow.cpp
        src/mainwindow.hpp
        src/mainwindow.ui
        src/myplot.hpp
        src/myplot.cpp
)

if(${QT_VERSION_MAJOR} GREATER_EQUAL 6)
    qt_add_executable(Front
        MANUAL_FINALIZATION
        ${PROJECT_SOURCES}
    )
# Define target properties for Android with Qt 6 as:
#    set_property(TARGET Front APPEND PROPERTY QT_ANDROID_PACKAGE_SOURCE_DIR
#                 ${CMAKE_CURRENT_SOURCE_DIR}/android)
# For more information, see https://doc.qt.io/qt-6/qt-add-executable.html#target-creation
else()
    if(ANDROID)
        add_library(Front SHARED
            ${PROJECT_SOURCES}
        )
# Define properties for Android with Qt 5 after find_package() calls as:
#    set(ANDROID_PACKAGE_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/android")
    else()
        add_executable(Front
            ${PROJECT_SOURCES}
        )
    endif()
endif()

# add QWT include and library directories to the project
target_include_directories(${PROJECT_NAME} PRIVATE ${QWT_INCLUDE_DIRS})
target_link_directories(${PROJECT_NAME} PRIVATE ${QWT_LIBRARIES})

target_link_libraries(Front PUBLIC
    Qt${QT_VERSION_MAJOR}::Widgets
    qwt
)

set_target_properties(Front PROPERTIES
    MACOSX_BUNDLE_GUI_IDENTIFIER my.example.com
    MACOSX_BUNDLE_BUNDLE_VERSION ${PROJECT_VERSION}
    MACOSX_BUNDLE_SHORT_VERSION_STRING ${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}
    MACOSX_BUNDLE TRUE
    WIN32_EXECUTABLE TRUE
)

install(TARGETS Front
    BUNDLE DESTINATION .
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})

if(QT_VERSION_MAJOR EQUAL 6)
    qt_finalize_executable(Front)
endif()

My MyPlot class header looks like this:

#ifndef MYPLOT_HPP
#define MYPLOT_HPP

#include "qwt_plot.h"
#include "qwt_scale_engine.h"
#include "qwt_plot_curve.h"
#include "qwt_plot_grid.h"
#include "qwt_scale_draw.h"
#include "qwt_symbol.h"
#include "qwt_legend.h"
#include "qwt_text.h"
#include "qwt_point_data.h"
#include "qwt_series_data.h"
#include "qwt_plot_zoomer.h"
#include "qwt_plot_magnifier.h"

class MyPlot : public QwtPlot
{
    Q_OBJECT
public:
    explicit MyPlot(QWidget *parent = nullptr);
};

#endif // MYPLOT_HPP

The implementation file is just an empty constructor.

This is the promoted classes for this widget.
Screenshot

What could I be missing? Thanks in advance.