dancing_kirby.cpp

A simple example for a delayed_send based application.

A simple example for a delayed_send based application.

// This example illustrates how to do time-triggered loops in CAF using
// delayed_send.
 
#include "caf/actor_system.hpp"
#include "caf/caf_main.hpp"
#include "caf/event_based_actor.hpp"
 
#include <algorithm>
#include <chrono>
#include <iostream>
 
using std::cout;
using std::endl;
using std::pair;
 
using namespace caf;
using namespace std::literals;
 
// ASCII art figures
constexpr const char* figures[] = {
  "<(^.^<)",
  "<(^.^)>",
  "(>^.^)>",
};
 
struct animation_step {
  size_t figure_idx;
  size_t offset;
};
 
// array of {figure, offset} pairs
constexpr animation_step animation_steps[] = {
  {1, 7},  {0, 7},  {0, 6},  {0, 5},  {1, 5},  {2, 5},  {2, 6},
  {2, 7},  {2, 8},  {2, 9},  {2, 10}, {1, 10}, {0, 10}, {0, 9},
  {1, 9},  {2, 10}, {2, 11}, {2, 12}, {2, 13}, {1, 13}, {0, 13},
  {0, 12}, {0, 11}, {0, 10}, {0, 9},  {0, 8},  {0, 7},  {1, 7},
};
 
constexpr size_t animation_width = 20;
 
// "draws" an animation step by printing "{offset_whitespaces}{figure}{padding}"
void draw_kirby(const animation_step& animation) {
  cout.width(animation_width);
  // override last figure
  cout << '\r';
  // print offset
  std::fill_n(std::ostream_iterator<char>{cout}, animation.offset, ' ');
  // print figure
  cout << figures[animation.figure_idx];
  // print padding
  cout.fill(' ');
  // make sure figure is printed
  cout.flush();
}
 
// --(rst-delayed-send-begin)--
// uses a message-based loop to iterate over all animation steps
behavior dancing_kirby(event_based_actor* self) {
  // let's get it started
  self->mail(update_atom_v, size_t{0}).send(self);
  return {
    [self](update_atom, size_t step) {
      if (step == sizeof(animation_step)) {
        // we've printed all animation steps (done)
        cout << endl;
        self->quit();
        return;
      }
      // print given step
      draw_kirby(animation_steps[step]);
      // schedule next animation step
      self->mail(update_atom_v, step + 1).delay(150ms).send(self);
    },
  };
}
// --(rst-delayed-send-end)--
 
void caf_main(actor_system& system) {
  system.spawn(dancing_kirby);
}
 
CAF_MAIN()