Animating Window Opacity

1#include <SDL.h>
2#include <iostream>
3#include <thread>
4
5void FadeWindow(
6  SDL_Window* window,
7  float start,
8  float end,
9  int duration_ms
10) {
11  // Number of opacity increments
12  const int steps = 50;
13  const float increment = (end - start) / steps;
14  const int delay = duration_ms / steps;
15
16  for (int i = 0; i <= steps; ++i) {
17    float opacity = start + (increment * i);
18    SDL_SetWindowOpacity(window, opacity);
19    std::this_thread::sleep_for(
20      std::chrono::milliseconds(delay));
21  }
22}
23
24int main() {
25  if (SDL_Init(SDL_INIT_VIDEO) < 0) {
26    std::cerr << "SDL Init Error: "
27      << SDL_GetError() << "\n";
28    return -1;
29  }
30
31  SDL_Window* window = SDL_CreateWindow(
32    "Fading Window",
33    SDL_WINDOWPOS_CENTERED,
34    SDL_WINDOWPOS_CENTERED,
35    400, 200, 0
36  );
37
38  if (!window) {
39    std::cerr << "Window Creation Error: "
40      << SDL_GetError() << "\n";
41    SDL_Quit();
42    return -1;
43  }
44  
45  // Fade out in 2 seconds
46  FadeWindow(window, 1.0f, 0.0f, 2000);
47
48  SDL_DestroyWindow(window);
49  SDL_Quit();
50  return 0;
51}