Centering Window on Specific Display

1#include <SDL.h>
2#include <iostream>
3
4void CenterWindowOnDisplay(
5  SDL_Window* window, int displayIndex
6) {
7  if (!window) {
8    std::cerr << "Window is null!\n";
9    return;
10  }
11
12  SDL_Rect displayBounds;
13  if (SDL_GetDisplayBounds(
14    displayIndex, &displayBounds
15  ) != 0) {
16    std::cerr << "Failed to get display "
17      "bounds: " << SDL_GetError() << "\n";
18    return;
19  }
20
21  int windowWidth, windowHeight;
22  SDL_GetWindowSize(
23    window, &windowWidth, &windowHeight);
24
25  int centeredX = displayBounds.x + (
26    displayBounds.w - windowWidth) / 2;
27  int centeredY = displayBounds.y + (
28    displayBounds.h - windowHeight) / 2;
29
30  SDL_SetWindowPosition(
31    window, centeredX, centeredY);
32}
33
34int main(int argc, char* argv[]) {
35  if (SDL_Init(SDL_INIT_VIDEO) != 0) {
36    std::cerr << "SDL_Init Error: "
37      << SDL_GetError() << "\n";
38    return 1;
39  }
40
41  SDL_Window* window = SDL_CreateWindow(
42    "Centered Window",
43    SDL_WINDOWPOS_CENTERED,
44    SDL_WINDOWPOS_CENTERED,
45    800, 600,
46    SDL_WINDOW_SHOWN
47  );
48
49  if (!window) {
50    std::cerr << "SDL_CreateWindow Error: "
51      << SDL_GetError() << "\n";
52    SDL_Quit();
53    return 1;
54  }
55
56  // Center the window on display 1 (change
57  // index as needed)
58  CenterWindowOnDisplay(window, 1);
59
60  // Wait 3 seconds to see the window
61  SDL_Delay(3000);
62
63  SDL_DestroyWindow(window);
64  SDL_Quit();
65  return 0;
66}