Purpose of SDL Window Events

Monitoring SDL window events is more efficient and practical than continuously polling for window properties. Here’s why:

Efficiency

Polling involves repeatedly checking the state of properties like size, position, or flags in every frame of the game loop. This wastes CPU cycles and can degrade performance, especially in high-performance applications where every frame counts.

SDL window events are only generated when a relevant change happens, such as the window being resized or moved. This event-driven approach ensures your program reacts only when necessary.

Simplified Logic

By relying on events, you avoid cluttering your game loop with unnecessary checks. This makes your code cleaner and easier to maintain. Instead of writing logic to track every property change manually, you can handle specific events like SDL_WINDOWEVENT_RESIZED or SDL_WINDOWEVENT_MOVED when they occur.

Access to Richer Data

Window events often include additional information about the change. For instance, the SDL_WINDOWEVENT_RESIZED event provides the new dimensions of the window, saving you from having to query these properties separately.

Here’s an example showing the difference. Polling might look like this:

1void CheckWindowState(SDL_Window* window) {
2  static int lastWidth = 0, lastHeight = 0;
3
4  int width, height;
5  SDL_GetWindowSize(window, &width, &height);
6
7  if (width != lastWidth || height != lastHeight) {
8    std::cout << "Window resized to "
9      << width << "x" << height << '\n';
10    lastWidth = width;
11    lastHeight = height;
12  }
13}

A more efficient event-driven approach would look like this:

1void HandleWindowEvent(SDL_WindowEvent& event) {
2  if (event.event == SDL_WINDOWEVENT_RESIZED) {
3    std::cout << "Window resized to "
4      << event.data1 << "x" << event.data2 << '\n';
5  }
6}

By using events, your program is responsive, efficient, and simpler to maintain.