i_font_size - updating of user defined widgets

The class Fl_Widget is ment as basic class for user defined classes. But it doesn't provide methods for text settings and often derived widgets will use text output. For adding such widgets to font and size system, they can be derive from i_font_size:
 struct i_font_size
    {    // Interface for adjustment of fonts and sizes for self defined widgets
        virtual unsigned char textsize() const= 0;
        virtual Fl_Font textfont() const= 0;
        virtual void textsize(unsigned char Size)= 0;
        virtual void textfont(Fl_Font Font)= 0;

It's a pure interface and you need to overwrite the methods to make the widget accessable by general setting of font and font size.

class Fl_My_Widget: public Fl_Widget, public i_font_size
        virtual unsigned char textsize() const    { return m_Size; }
        virtual Fl_Font textfont() const  { return m_Font; }
        virtual void textsize(unsigned char Size)    { m_Size= Size; }
        virtual void textfont(Fl_Font Font) { m_Font= Font; }

        Fl_Font    m_Font;
        unsigned char m_Size;

It is not necessary to use this interface, when the new widget was derived from a class, that provides methods textsize(), textfont().

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