Handling Multi-Window Events

How does SDL handle events when there are multiple windows?

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:

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

Retrieving the Window

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

SDL_Window* window = SDL_GetWindowFromID(
  event.window.windowID);
if (window) {
  SDL_SetWindowTitle(
    window, "Event Triggered"
  );
}

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:

void HandleResize(SDL_WindowEvent& event) {
  SDL_Window* window =
    SDL_GetWindowFromID(event.windowID);
  if (window) {
    std::cout << "Resized window with ID "
      << event.windowID << '\n';
  }
}

void ProcessEvents() {
  SDL_Event event;
  while (SDL_PollEvent(&event)) {
    if (event.type == SDL_WINDOWEVENT &&
        event.window.event == SDL_WINDOWEVENT_RESIZED) {
      HandleResize(event.window);
    }
  }
}

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

Multiple Windows and Utility Windows

Learn how to manage multiple windows, and practical examples using utility windows.

Questions & Answers

Answers are generated by AI models and may not have been reviewed. Be mindful when running any code on your device.

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What happens if we don't destroy a window before exiting the program?
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