why are the Widgets not showing on this gtkmm4 application? - user-interface

Question

Hi I recently tried to update this application to gtkmm4, however I am not finding anyway to have the widgets shown in the application. I have found that the function show_al() has been removed because the widgets now are to be visible by default, so I really don't understand why.
main:
#include <iostream>
#include "config.h"
#ifdef ENABLE_NLS
# include <libintl.h>
#endif
#include "u-i-controller.h"
/* For testing propose use the local (not installed) ui file */
/* #define UI_FILE PACKAGE_DATA_DIR"/ui/time_keeper.ui" */
#define UI_FILE "src/time_keeper.ui"
Gtk::ApplicationWindow * main_win = nullptr;
Glib::RefPtr<Gtk::Builder> builder = nullptr;
void activate_app(Gtk::Application * app)
{
app->add_window(*main_win);
//Load the Glade file and instiate its widgets:
try
{
builder = Gtk::Builder::create_from_file(UI_FILE);
main_win = (Gtk::ApplicationWindow*) builder->get_widget<Gtk::ApplicationWindow>("main_window");
}
catch (const Glib::FileError & ex)
{
std::cerr << ex.what() << std::endl;
}
main_win->show();
//return app->run(helloworld, argc, argv);
//main_win->show_all_children ();
//main_win->show_all_children ()
}
int
main (int argc, char *argv[])
{
auto app = Gtk::Application::create("org.gtkmm.time_keeper");
return app->make_window_and_run<Gtk::ApplicationWindow>(argc, argv);
if (main_win)
{
app->signal_startup().connect(sigc::bind<0/*,Gtk::Application**/>(sigc::ptr_fun(&activate_app), app.get() ) );
UI_Controller * controller = new UI_Controller(builder.get(),app.get());
}
}
ui file:
<interface>
<requires lib="gtk" version="4.0"/>
<object class="GtkApplicationWindow" id="main_window">
<child>
<object class="GtkBox">
<property name="orientation">vertical</property>
<property name="spacing">13</property>
<property name="homogeneous">1</property>
<child>
<object class="GtkScrolledWindow">
<property name="focusable">1</property>
<!--property name="shadow-type">in</property-->
<property name="child">
<object class="GtkViewport">
<property name="child">
<object class="GtkBox">
<property name="orientation">vertical</property>
<child>
<object class="GtkLabel">
<property name="label" translatable="yes">current activity time</property>
</object>
</child>
<child>
<object class="GtkGrid" id="timer_grid">
<property name="hexpand">1</property>
<property name="vexpand">1</property>
<child>
<object class="GtkEntry">
<property name="focusable">1</property>
<property name="hexpand">1</property>
<layout>
<property name="column">0</property>
<property name="row">0</property>
<property name="column-span">3</property>
</layout>
</object>
</child>
<child>
<object class="GtkButton" id="start_timer">
<property name="label" translatable="yes">Start</property>
<property name="focusable">1</property>
<property name="receives-default">1</property>
<layout>
<property name="column">0</property>
<property name="row">2</property>
</layout>
</object>
</child>
<child>
<object class="GtkButton" id="stop_timer">
<property name="label" translatable="yes">Stop</property>
<property name="focusable">1</property>
<property name="receives-default">1</property>
<layout>
<property name="column">1</property>
<property name="row">2</property>
</layout>
</object>
</child>
<child>
<object class="GtkButton" id="restart_timer">
<property name="label" translatable="yes">Restart</property>
<property name="focusable">1</property>
<property name="receives-default">1</property>
<layout>
<property name="column">2</property>
<property name="row">2</property>
</layout>
</object>
</child>
<child>
<object class="GtkButton" id="add_timer">
<property name="label" translatable="yes">+</property>
<property name="focusable">1</property>
<property name="receives-default">1</property>
<layout>
<property name="column">3</property>
<property name="row">0</property>
<property name="row-span">3</property>
</layout>
</object>
</child>
<child>
<object class="GtkLabel" id="timer_display">
<property name="hexpand">1</property>
<property name="vexpand">1</property>
<layout>
<property name="column">0</property>
<property name="row">1</property>
<property name="column-span">3</property>
</layout>
</object>
</child>
</object>
</child>
</object>
</property>
</object>
</property>
</object>
</child>
<child>
<object class="GtkScrolledWindow">
<property name="focusable">1</property>
<!--property name="shadow-type">in</property-->
<property name="child">
<object class="GtkViewport">
<property name="child">
<object class="GtkBox">
<property name="orientation">vertical</property>
<child>
<object class="GtkLabel">
<property name="label" translatable="yes">activity limit</property>
</object>
</child>
<child>
<object class="GtkGrid" id="counter_grid">
<property name="hexpand">1</property>
<property name="vexpand">1</property>
<child>
<object class="GtkEntry">
<property name="focusable">1</property>
<property name="hexpand">1</property>
<layout>
<property name="column">0</property>
<property name="row">0</property>
<property name="column-span">3</property>
</layout>
</object>
</child>
<child>
<object class="GtkButton">
<property name="label" translatable="yes">Start</property>
<property name="focusable">1</property>
<property name="receives-default">1</property>
<layout>
<property name="column">0</property>
<property name="row">2</property>
</layout>
</object>
</child>
<child>
<object class="GtkButton">
<property name="label" translatable="yes">Stop</property>
<property name="focusable">1</property>
<property name="receives-default">1</property>
<layout>
<property name="column">1</property>
<property name="row">2</property>
</layout>
</object>
</child>
<child>
<object class="GtkButton">
<property name="label" translatable="yes">Restart</property>
<property name="focusable">1</property>
<property name="receives-default">1</property>
<layout>
<property name="column">2</property>
<property name="row">2</property>
</layout>
</object>
</child>
<child>
<object class="GtkButton">
<property name="label" translatable="yes">+</property>
<property name="focusable">1</property>
<property name="receives-default">1</property>
<layout>
<property name="column">3</property>
<property name="row">0</property>
<property name="row-span">3</property>
</layout>
</object>
</child>
<child>
<object class="GtkLabel">
<property name="hexpand">1</property>
<property name="vexpand">1</property>
<layout>
<property name="column">2</property>
<property name="row">1</property>
</layout>
</object>
</child>
<child>
<object class="GtkEntry">
<property name="focusable">1</property>
<property name="hexpand">1</property>
<layout>
<property name="column">0</property>
<property name="row">1</property>
<property name="column-span">2</property>
</layout>
</object>
</child>
</object>
</child>
</object>
</property>
</object>
</property>
</object>
</child>
</object>
</child>
</object>
</interface>
those are the most warnings that I receive but I dont think it has much to do with it:
(time_keeper:620): Gtk-WARNING **: 17:22:19.139: Unknown key gtk-menu-images in ~/.config/gtk-4.0/settings.ini
(time_keeper:620): Gtk-WARNING **: 17:22:19.139: Unknown key gtk-toolbar-style in ~/.config/gtk-4.0/settings.ini