Cross Platform Widgets Toolkit -- Better Approach

crossplatform_widgets__better.cpp

namespace ToolkitCode {
    class IButton {
        virtual void setTitle(const string &title) = 0;
        virtual void doOnClick(std::function<void()> handler) = 0;
    };

    class Win32APIButton : public IButton {
        virtual void setTitle(const string &title) = 0;
        virtual void doOnClick(std::function<void()> handler) = 0;
    };

    class WinFormsButton : public IButton  {
        virtual void setTitle(const string &title) = 0;
        virtual void doOnClick(std::function<void()> handler) = 0;
    };

    class GTKButton : public IButton  {
        virtual void setTitle(const string &title) override;
        virtual void doOnClick(std::function<void()> handler) override;
    };

    class QtButton : public IButton  {
        virtual void setTitle(const string &title) = 0;
        virtual void doOnClick(std::function<void()> handler) override;
    };
}

interface IWidgetsFactory { 
public:
    IButton *createButton();
};

class Win32APIWidgetsFactory : public IWidgetsFactory {
public:    
    IButton *createButton() { return Win32APIButton(); }
    IComboBox *createComboBox() { return Win32ComboBox(); }
};

class GTKWidgetsFactory : public IWidgetsFactory {
public:    
    IButton *createButton() { return GTKAPIButton(); }
    IComboBox *createComboBox() { return GTKComboBox(); }
};

class QtWidgetsFactory : public IWidgetsFactory {
public:    
    IButton *createButton() { return QtAPIButton(); }
    IComboBox *createComboBox() { return QtComboBox(); }
};

namespace ClientCode {
    enum class UIFlavor {
        GTK,
        WinForms,
        Win32,
        QT
    };

    class ProgramOptions {
        uiFlavor: UIFlavor;
    };

    void createUI() {
        IButton *createDocumentButton,
                *saveDocumentButton,
                *loadDocumentButton;
        IWidgetsFactory *widgetsFactory;

        ProgramOptions options = getActualOptions();

        if (options.uiFlavor == GTK) {
            widgetsFactory = new GTKWidgetsFactory();
        } else if (options.uiFlavor == WinForms) {
            widgetsFactory = WinFormsWidgetsFactory(); 
        } else if (options.uiFlavor == Win32) {
            widgetsFactory = Win32WidgetsFactory(); 
        } else if (options.uiFlavor == Qt) {
            widgetsFactory = QtWidgetsFactory(); 
        }

        createDocumentButton = widgetsFactory->createButton();
        saveDocumentButton = widgetsFactory->createButton();
        loadDocumentButton = widgetsFactory->createButton();
    }
};