widget.h

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#pragma once
 
#include <functional>
#include <memory>
#include <string>
#include <type_traits>
 
#include <stdint.h>
 
#include "rbjson.h"
 
#include "../widgets/widget.h"
 
namespace gridui {
 
class _GridUi;
 
namespace builder {
 
template <typename Self, typename Constructed>
class BuilderMixin {
    // The Self is not fully defined yet here, so the check won't compile.
    //static_assert(std::is_base_of<Widget, Self>::value, "Self must inherit from Widget.");
    static_assert(std::is_base_of<gridui::Widget, Constructed>::value, "Constructed must inherit from gridui::Widget.");
 
    friend class gridui::_GridUi;
 
public:
    typedef std::function<void(Constructed&)> callback_t;
 
    Self& css(const std::string& key, const std::string& value) {
        auto& s = self();
        s.style().set(key, value);
        return s;
    }
 
    Constructed finish() {
        return Constructed(&self().m_state);
    }
 
protected:
    void addCallback(const std::string& name, callback_t cb) {
        auto* cbHeap = static_cast<void*>(new callback_t(cb)); // fuj
        self().m_state.addCallback(&callbackTrampoline, &callbackDeleter, name, cbHeap);
    }
 
private:
    Self& self() { return *static_cast<Self*>(this); }
    const Self& self() const { return *static_cast<Self*>(this); }
 
    static void callbackTrampoline(void* cb, WidgetState* state) {
        Constructed w(state);
        (*static_cast<callback_t*>(cb))(w);
    }
 
    static void callbackDeleter(void *cb) {
        auto *cb_typed = static_cast<callback_t*>(cb);
        delete cb_typed;
    }
};
 
class Widget {
    friend class gridui::_GridUi;
 
    template <typename Self, typename Finished>
    friend class BuilderMixin;
 
public:
    Widget(Widget&& o) noexcept;
    virtual ~Widget();
 
protected:
    Widget(const char* type, WidgetState& state);
 
    virtual void serialize(std::stringstream& ss);
 
    rbjson::Object& extra();
    rbjson::Object& style();
 
    WidgetState& m_state;
 
private:
    Widget(const Widget&) = delete;
    Widget& operator=(const Widget&) = delete;
 
    const char* m_type;
    rbjson::Object* m_style;
};
 
};
};