Why Use SDL_GetWindowFromID()?

SDL_GetWindowFromID() is particularly useful in scenarios where you are managing multiple windows and only have the window ID, not the pointer. While passing a SDL_Window* directly is simpler, here's why you might prefer using SDL_GetWindowFromID():

Events Are Window ID-Based

When handling SDL events, window-related events, like SDL_WINDOWEVENT, provide only the window ID (event.window.windowID). To interact with the corresponding window, you must use SDL_GetWindowFromID() to retrieve its pointer.

Safety

Using window IDs ensures that you're accessing the correct window, especially if windows are dynamically created and destroyed. A pointer might become invalid if the window it references is destroyed.

Example Usage

Here's an example where we get a window ID from an SDL_Window*, and an SDL_Window* from a window ID:

1#include <SDL.h>
2#include <iostream>
3
4int main() {
5  if (SDL_Init(SDL_INIT_VIDEO) < 0) {
6    std::cerr << "SDL Init Error: "
7      << SDL_GetError() << "\n";
8    return -1;
9  }
10
11  SDL_Window* window = SDL_CreateWindow(
12    "Window Example",
13    SDL_WINDOWPOS_CENTERED,
14    SDL_WINDOWPOS_CENTERED,
15    400, 300,
16    SDL_WINDOW_SHOWN
17  );
18
19  if (!window) {
20    std::cerr << "Window Creation Error: "
21      << SDL_GetError() << "\n";
22    SDL_Quit();
23    return -1;
24  }
25
26  Uint32 windowID = SDL_GetWindowID(window);
27
28  SDL_Window* retrieved =
29    SDL_GetWindowFromID(windowID);
30    
31  if (retrieved == window) {
32    std::cout << "Successfully retrieved "
33      "the window from ID!\n";
34  }
35
36  SDL_DestroyWindow(window);
37  SDL_Quit();
38  return 0;
39}

1Successfully retrieved the window from ID!

Using IDs is safer and integrates better with SDL's event-driven architecture.