Handling Multi-Window Events

SDL provides robust support for managing multiple windows in an application. Each window created with SDL_CreateWindow() is assigned a unique identifier (windowID), which SDL uses to associate events with the correct window.

Event Structure

When an event occurs that relates to a specific window, like a resize or keypress, the event structure includes the windowID. This allows your program to determine which window the event corresponds to.

For example, in a SDL_WindowEvent:

1if (event.type == SDL_WINDOWEVENT) {
2  std::cout << "Event for Window ID: "
3            << event.window.windowID << '\n';
4}

Retrieving the Window

To get the SDL_Window* associated with an event, use SDL_GetWindowFromID():

1SDL_Window* window = SDL_GetWindowFromID(
2  event.window.windowID);
3if (window) {
4  SDL_SetWindowTitle(
5    window, "Event Triggered"
6  );
7}

Example Use Case

Imagine a multi-window text editor. Each window represents a document, and resizing one window shouldn’t affect the others. Here’s a simplified example:

1void HandleResize(SDL_WindowEvent& event) {
2  SDL_Window* window =
3    SDL_GetWindowFromID(event.windowID);
4  if (window) {
5    std::cout << "Resized window with ID "
6      << event.windowID << '\n';
7  }
8}
9
10void ProcessEvents() {
11  SDL_Event event;
12  while (SDL_PollEvent(&event)) {
13    if (event.type == SDL_WINDOWEVENT &&
14        event.window.event == SDL_WINDOWEVENT_RESIZED) {
15      HandleResize(event.window);
16    }
17  }
18}

Using window IDs ensures you can efficiently manage events for each window independently, enabling complex multi-window applications.