Reduce style output

[fl4p]

Hi,

I am using this asciichart on a ESP32 micro controller. Resources are limited and the current implementation generates a lot of unnessary styling set & unset sequences.

We can omit styling when two consecutive text elements share the same style. C++ has a stream state API, that we can use to store information about the current style.

This works for me
Here's my implementation: (Note that you need to un-set the style at each line-end: std::cout << ascii::Decoration::From(ascii::Decoration::RESET) << "\n";):

text.h:

  friend std::ostream &operator<<(std::ostream &os, const Text &val) {

      std::stringstream ss;
      ss << val.style_;
      std::hash<std::string> hasher;
      auto textStyleHash = (long)hasher(ss.str());

      auto &streamStyleHash = os.iword(get_style_stream_iword());

      if(textStyleHash == streamStyleHash)
        os << val.text_;
      else {
          os << val.style_ << val.text_; // << Decoration::From(Decoration::RESET);
          streamStyleHash = textStyleHash;
      }
    return os;
  }

inline int get_style_stream_iword() {
    static int i = std::ios_base::xalloc();
    return i;
}