RxTerm

What is RxTerm?

RxTerm is a header-only C++ library for building terminal UIs using functional-reactive principles. It renders rich, animated output entirely via ANSI escape sequences — no ncurses, no platform-specific console API.

How it works

RxTerm models terminal output as a pure function of state. On each update it:

1. Computes the new screen as a string of ANSI-annotated characters
2. Diffs it against the previous frame
3. Writes only the changed cells using ESC[row;colH cursor positioning and ESC[2K line clearing

This is exactly the technique covered in the Terminal Escape Sequences slides — cursor positioning, line clearing, and colour codes working together to create smooth in-place animation.

Core API

#include <rxterm/terminal.hpp>
#include <rxterm/style.hpp>
#include <rxterm/components/text.hpp>
#include <rxterm/components/stacklayout.hpp>
 
using namespace rxterm;
 
auto render(VirtualTerminal vt, int i) {
  return vt.flip(
    StackLayout<>{
      Text("Hello, " + std::to_string(i) + "!", Style{ Color::Green }),
    }
  );
}
 
int main() {
  auto vt = VirtualTerminal{};
  for (int i = 0; i < 100; ++i) {
    vt = render(vt, i);
    std::this_thread::sleep_for(std::chrono::milliseconds(30));
  }
}

Features

• ✅ ANSI colour output (16-color + 256-color)
• ✅ Reusable components (Text, StackLayout, …)
• ✅ Functional / immutable update model
• ⬜ Managed console input
• ⬜ Terminal width detection
• ⬜ Full Windows support (works in msys2/mingw/cygwin)

Building

Requires C++14 and either Buck or Bazel:

buckaroo install
buck run :main      # or: bazel run :main