CMakeLists.txt

add_subdirectory("${CMAKE_CURRENT_LIST_DIR}/../SDL" SDL)

add_executable(vsync "${CMAKE_CURRENT_LIST_DIR}/vsync.cc")
target_link_libraries(vsync PRIVATE SDL3::SDL3)

sdl-vsync-test.cc

#include "SDL3/SDL.h"

#include <cassert>

int main() {
    SDL_Window* w = SDL_CreateWindow("vsync", 0, 0, 1280, 720, 0); assert(w);
    SDL_Renderer* r = SDL_CreateRenderer(w, "opengl", 0); assert(r);

    SDL_Log("Available render drivers:\n");
    for (int i = 0; i < SDL_GetNumRenderDrivers(); ++i) {
        SDL_Log("[%d] => %s\n", i, SDL_GetRenderDriver(i));
    }

    float then = 0.0f;
    bool vsync = false;
    bool running = true;
    do {
        SDL_Event evt = { };
        while (SDL_PollEvent(&evt)) {
            if (evt.type == SDL_QUIT) { running = false; }
            if (evt.type == SDL_KEYDOWN && evt.key.keysym.sym == SDLK_ESCAPE) {
                running = false;
            }
            if (evt.type == SDL_KEYDOWN && evt.key.keysym.sym == SDLK_v) {
                vsync = !vsync;
                if (SDL_RenderSetVSync(r, vsync) != 0) {
                    SDL_Log("SDL_RenderSetVSync failed: %s\n", SDL_GetError());
                    running = false;
                }
                SDL_Log("Set VSync to %d\n", vsync);
            }
        }

        SDL_RenderClear(r);
        SDL_RenderPresent(r);

        float now = SDL_GetTicks() / 1e3f;
        float dt = now - then;
        then = now;

        SDL_Log("Frame now=%f dt=%f fps=%.0f\n", now, dt, 1.0f / dt);
        SDL_Log("SDL_RenderGetVSync(): %d\n", SDL_RenderGetVSync(r));

        SDL_Delay(1000/100);
    } while (running);

    SDL_DestroyRenderer(r);
    SDL_DestroyWindow(w);
}