It's not true that the relevant source is in SDL - clock.tick does call SDL_Delay, but all SDL_Delay takes a number of ticks to sleep, and then just sleeps that long. It's pygame source that is deciding how long to sleep/wait.
... also no need to guess at the source, you can get at it from the web, even: http://www.seul.org/viewcvs/viewcvs.cgi/trunk/src/time.c?rev=1240&root=PyGame&view=auto Basically, I think this could be fixed in pygame source without an SDL change, just by putting a max on how long to wait in clock tick - and that delay could be maxed out at the framerate (surely you never would wait longer than 100ms to regulate a 10fps timer, right?) here's the relevant source (accurate_delay is passed in as 0, and the framerate arg is what was passed to tick): ---------------------------- // to be called by the other tick functions. static PyObject* clock_tick_base(PyObject* self, PyObject* arg, int use_accurate_delay) { PyClockObject* _clock = (PyClockObject*) self; float framerate = 0.0f; int nowtime; if (!PyArg_ParseTuple (arg, "|f", &framerate)) return NULL; if (framerate) { int delay, endtime = (int) ((1.0f / framerate) * 1000.0f); _clock->rawpassed = SDL_GetTicks () - _clock->last_tick; delay = endtime - _clock->rawpassed; /*just doublecheck that timer is initialized*/ if (!SDL_WasInit (SDL_INIT_TIMER)) { if (SDL_InitSubSystem (SDL_INIT_TIMER)) { RAISE (PyExc_SDLError, SDL_GetError ()); return NULL; } } if (use_accurate_delay) delay = accurate_delay (delay); else { // this uses sdls delay, which can be inaccurate. if (delay < 0) delay = 0; Py_BEGIN_ALLOW_THREADS; SDL_Delay ((Uint32) delay); Py_END_ALLOW_THREADS; } if (delay == -1) return NULL; } nowtime = SDL_GetTicks (); _clock->timepassed = nowtime - _clock->last_tick; _clock->fps_count += 1; _clock->last_tick = nowtime; if (!framerate) _clock->rawpassed = _clock->timepassed; if (!_clock->fps_tick) { _clock->fps_count = 0; _clock->fps_tick = nowtime; } else if (_clock->fps_count >= 10) { _clock->fps = _clock->fps_count / ((nowtime - _clock->fps_tick) / 1000.0f); _clock->fps_count = 0; _clock->fps_tick = nowtime; Py_XDECREF (_clock->rendered); } return PyInt_FromLong (_clock->timepassed); }
