emsdk/upstream/emscripten/test/emscripten_request_animation_frame.c

#include <emscripten/html5.h>
#include <assert.h>

int func1Executed = 0;
int func2Executed = 0;

bool func1(double time, void *userData);

bool func2(double time, void *userData) {
  assert((long)userData == 2);
  assert(time > 0);
  ++func2Executed;

  if (func2Executed == 1) {
    // Test canceling an animation frame: register rAF() but then cancel it immediately
    long id = emscripten_request_animation_frame(func1, (void*)2);
    emscripten_cancel_animation_frame(id);

    emscripten_request_animation_frame(func2, (void*)2);
  }
  if (func2Executed == 2) {
    assert(func1Executed == 1);
  }
  return 0;
}

bool func1(double time, void *userData) {
  assert((long)userData == 1);
  assert(time > 0);
  ++func1Executed;

  assert(func1Executed == 1);

  emscripten_request_animation_frame(func2, (void*)2);

  return 0;
}

int main() {
  emscripten_request_animation_frame(func1, (void*)1);
}