foo_bar.cpp

# include "ui/button.h.cpp"
# include "ui/pane.h.cpp"
# include "ui/tooltip.h.cpp"
# include "ui/typography.h.cpp"

# include "wtk/event.h.cpp"
# include "wtk/render.h.cpp"
# include "wtk/state.h.cpp"
# include "wtk/style.h.cpp"
# include "wtk/tree.h.cpp"
# include "wtk/widget.h.cpp"

namespace foo {
    
    class bar : public wtk::widget<bar> {
        
        private:
            void handle_click (wtk::event event) {
                widget_state.emplace("click_count", widget_state.at<int>("click_count") + 1);
            }
        
        protected:
            wtk::state create () override {
                return {
                    { "click_count", 0 }
                };
            }
        
            wtk::style design () override {
                return {
                    { "foo_bar",
                        {
                            { "height", 240 },
                            { "width", 640 }
                        }
                    }
                };
            }
        
            wtk::tree render () override {
                int click_count = widget_state.at<int>("click_count");
                
                return {
                    wtk::render<ui::pane>({ { "id", "foo_bar" }, { "layout", "vertical" } }, {
                        wtk::render<ui::typography>({ { "variant", "title" }, {
                            "this is a title",
                            wtk::render<ui::typography>({ { "variant", "bold" } }, {
                                "this is bold"
                            });
                        }),
                        wtk::render<ui::button>({ { "on_click", this->handle_click } }, { 
                            "click me (" + click_count + ")" 
                        }),
                        wtk::render<ui::tooltip>({ { "hidden", false }, {
                            "click the button to increment the count"
                        })
                    })
                };
            }
    }
}

widget.cpp

# pragma once

# include "fusion/emitter.h.cpp"

# include "wtk/event.h.cpp"
# include "wtk/factory.h.cpp"
# include "wtk/props.h.cpp"
# include "wtk/state.h.cpp"
# include "wtk/style.h.cpp"
# include "wtk/tree.h.cpp"

namespace wtk {

    template <typename widget_type> class widget : public fusion::emitter<wtk::event*> {
        friend wtk::factory;

        private:
            wtk::props widget_props;
            wtk::state widget_state;
            wtk::style widget_style;
        
        protected:
            explicit widget () {

            }

            virtual wtk::state create () {
                return { };
            }

            virtual wtk::style design () {
                return { };
            }

            virtual wtk::tree render () {
                return { };
            }
    };
}