[einpoklum]

Well, the question of what's "modern" in C++ is both deep and contentions. But I won't shirk the question...

You want to be utilizing the features C++11, C++14 and maybe even newer versions of the standard allow you to use, to avoid unnecessary boilerplate, repetition, and arcane-ness of syntax and semantics.

Similarly, the GUI toolkit should not be based on C-like or C++98-like design patterns, when newer versions of the standard allow replacing them with more convenient patterns.

Here's one example, from the Nana C++ GUI toolkit:

  #include <nana/gui.hpp>
  #include <nana/gui/widgets/label.hpp>
  #include <nana/gui/widgets/button.hpp>

  int main() {
      nana::form form;

      nana::label label{form, "Hello, <bold blue size=16>Nana C++ Library</>"};
      label.format(true);

      nana::button button{form, "Quit"};
      button.events().click( [&form]{ form.close(); } );

      form.div("vert <><<><weight=80% text><>><><weight=24<><button><>><>");
      form["text"] << label;
      form["button"] << button;
      form.collocate();
 
      form.show();
 
      //Start to event loop process, it blocks until the form is closed.
      nana::exec();
  }

This is not perfect IMHO; for example, I don't really like the confusing div string with the many < and > signs. But you can put this in a text editor, build it with `g++ -I/path/to/nana/includes -L/path/to/nana/libs -lnana` - and it will just work, on various platforms. No secret sauce, no need for a bunch of IDE dialogs or any special configuration or action.

[jcelerier]

Here's a quick port to Qt (except for the <> thing which I did not really understand after a cursory reading of its docs)

    #include <QtWidgets>

    int main(int argc, char **argv) {
      QApplication app{argc, argv};
      QWidget widg;
      QVBoxLayout form{&widg};

      QLabel label{
          R"(Hello, <span style="font-weight: 600; font-size: 16pt; color: blue;">Qt C++ Library</span>)"};

      QPushButton button{"Quit"};
      button.connect(&button, &QPushButton::clicked, [&widg] { widg.close(); });

      form.addStretch(0.1);
      form.addWidget(&label);
      form.addStretch(0.7);
      form.addWidget(&button);
      form.addStretch(0.2);

      widg.show();

      app.exec();
    }

Builds with

    g++ example.cpp -I/usr/include/qt/ -I/usr/include/qt/QtWidgets -fPIC -lQt5Widgets -lQt5Core

Here's also how the two programs behave in practice: https://streamable.com/brltmc

tl;ds: now that I saw it in action, I know I can instantly ignore anyone who says that nana is a suitable replacement for Qt.