I was thinking about how it'd be interesting to write a "printer" simulator in lua so I could render various printer outputs that have different ESC codes... like Imagewriter ESC codes, 'cuz I'm dying to print dot matrix output in color.

I made a luaprinter class and I've got it so it can render to a bitmap.

Just a proof of concept.

class luaprinter {


        const static int BUFFERSIZE = 128000;  // a nice big size so we shouldn't have to worry
        int m_printerbuffer[BUFFERSIZE];
        int m_head = 0;
        int m_tail = 0;
        bitmap_rgb32 *m_bitmap;  // pointer to bitmap
        int m_xpos = 0;
        int m_ypos = 0;

        virtual void clearpage(){ m_bitmap->fill(0);};
        virtual void drawpixel(int x, int y, int pixelval){m_bitmap->pix32(y,x) = pixelval; };  // row major
        virtual int getpixel(int x, int y){return m_bitmap->pix32(y,x);};
        virtual void setheadpos(int x, int y){m_xpos=x;m_ypos=y;};
        virtual void savepage(){};
        virtual std::tuple<int*,int,int>  getbuffer() { return std::make_tuple(m_printerbuffer,m_head,m_tail);};   // returns the entire buffer as an integer a>
        virtual int getnextchar(){if (m_head==m_tail) return -1; else { int retval = m_printerbuffer[m_tail++]; m_tail %= BUFFERSIZE; return retval;}};
        virtual void putnextchar(int c){m_printerbuffer[m_head++]=c; m_head %= BUFFERSIZE;};
        void register_bitmap(bitmap_rgb32 &mybitmap){m_bitmap = &mybitmap;}  //
        void  testmodifybuffer(){ for (int i=0;i<10;i++){  m_printerbuffer[i]=i; m_head++;  };  };
        std::tuple<int,int>getheadpos() { return std::make_tuple(m_xpos,m_ypos); };

        static std::vector<luaprinter *> luaprinterlist;

and then hack on centronics/printer.cpp to inherit from luaprinter, and do a little bit of hookups in luaengine.

        auto luaprinter_type = sol().registry().create_simple_usertype<luaprinter>("new", sol::no_constructor);
        luaprinter_type.set("clearpage", &luaprinter::clearpage);
        luaprinter_type.set("drawpixel", &luaprinter::drawpixel);
        luaprinter_type.set("getpixel", &luaprinter::getpixel);
        luaprinter_type.set("setheadpos", &luaprinter::setheadpos);
        luaprinter_type.set("savepage", &luaprinter::savepage);
        luaprinter_type.set("getbuffer", &luaprinter::getbuffer);
        luaprinter_type.set("getnextchar", &luaprinter::getnextchar);
        luaprinter_type.set("getheadpos", &luaprinter::getheadpos);
        sol().registry().set_usertype("luaprinter", luaprinter_type);

        machine_type.set("luaprinters", sol::property([this](running_machine &m) {
                        sol::table table = sol().create_table();
                        int i=0;
                        for(luaprinter* p : luaprinter::luaprinterlist)
                                table[i++] = &(*p);
                        return table;

I haven't worked it all out yet and I'm figuring out all this cpp stuff (and sometimes not figuring it out 8-) but I did get it to draw on my bitmap:
for i=0,255 do for p=0,7 do 
if (2^p) & i ~= 0 then 
end end end

[Linked Image from i.imgur.com]

And it wouldn't be hard at all to do color:
[Linked Image from i.imgur.com]
function iff(a,b,c) if a~=0 then return b else return c end end
for i=0,255 do 
for p=0,7 do 
if (2^p) & i ~= 0 then 
end end end