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Code Issues Releases Wiki Activity

new timing scheme which should eliminate speedups

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thanks to opmox for initial implementation
This commit is contained in:
fgsfds 2020-11-02 19:32:54 +03:00
parent 2cf99649d8
commit 68e6e60a03
1 changed files with 35 additions and 10 deletions
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45
src/pc/gfx/gfx_sdl2.c
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@ -24,6 +24,7 @@
#endif // End of OS-Specific GL defines
#include <stdint.h>
#include <stdio.h>
#include <unistd.h>
@ -52,8 +53,10 @@ static void (*kb_all_keys_up)(void) = NULL;
// whether to use timer for frame control
static bool use_timer = true;
// time between consequtive game frames
static const int frame_time = 1000 / FRAMERATE;
// time between consequtive game frames, in perf counter ticks
static double frame_time = 0.0; // set in init()
// GetPerformanceFrequency
static double perf_freq = 0.0;
const SDL_Scancode windows_scancode_table[] = {
/* 0 1 2 3 4 5 6 7 */
@ -107,7 +110,12 @@ const SDL_Scancode scancode_rmapping_nonextended[][2] = {
#define IS_FULLSCREEN() ((SDL_GetWindowFlags(wnd) & SDL_WINDOW_FULLSCREEN_DESKTOP) != 0)
int test_vsync(void) {
static inline void sys_sleep(const uint64_t us) {
// TODO: not everything has usleep()
usleep(us);
}
static int test_vsync(void) {
// Even if SDL_GL_SetSwapInterval succeeds, it doesn't mean that VSync actually works.
// A 60 Hz monitor should have a swap interval of 16.67 milliseconds.
// Try to detect the length of a vsync by swapping buffers some times.
@ -224,6 +232,9 @@ static void gfx_sdl_init(const char *window_title) {
gfx_sdl_set_fullscreen();
perf_freq = SDL_GetPerformanceFrequency();
frame_time = perf_freq / FRAMERATE;
for (size_t i = 0; i < sizeof(windows_scancode_table) / sizeof(SDL_Scancode); i++) {
inverted_scancode_table[windows_scancode_table[i]] = i;
}
@ -327,13 +338,27 @@ static bool gfx_sdl_start_frame(void) {
}
static inline void sync_framerate_with_timer(void) {
static Uint32 last_time = 0;
// get base timestamp on the first frame (might be different from 0)
if (last_time == 0) last_time = SDL_GetTicks();
const int elapsed = SDL_GetTicks() - last_time;
if (elapsed < frame_time)
SDL_Delay(frame_time - elapsed);
last_time += frame_time;
static double last_time;
static double last_sec;
static int frames_since_last_sec;
const double now = SDL_GetPerformanceCounter();
frames_since_last_sec += 1;
if (last_time) {
const double elapsed = last_sec ? (now - last_sec) : (now - last_time);
if ((elapsed < frame_time && !last_sec) || (elapsed < frames_since_last_sec * frame_time && last_sec)) {
const double delay = last_sec ? frames_since_last_sec * frame_time - elapsed : frame_time - elapsed;
usleep(delay / perf_freq * 1000000.0);
last_time = now + delay;
} else {
last_time = now;
}
if ((int64_t)(now / perf_freq) > (int64_t)(last_sec / perf_freq)) {
last_sec = last_time;
frames_since_last_sec = 0;
}
} else {
last_time = now;
}
}
static void gfx_sdl_swap_buffers_begin(void) {