SDL_RaiseWindow() vs SDL_SetWindowInputFocus()

SDL_RaiseWindow() and SDL_SetWindowInputFocus() are both functions used to manage window focus in SDL, but they serve slightly different purposes and behave differently.

SDL_RaiseWindow()

The SDL_RaiseWindow() function brings the specified window to the front, making it the top-most window. It also attempts to grab input focus, ensuring that the window can receive user input.

This function is useful when you want to ensure that your window is visible and ready for user interaction. Here's an example:

1SDL_Window* MyWindow{GameWindow.SDLWindow};
2SDL_RaiseWindow(MyWindow);

When you call SDL_RaiseWindow(), it makes your window visible and attempts to give it input focus. This is particularly useful if your window is obscured by other windows and you want to bring it to the user's attention.

SDL_SetWindowInputFocus()

The SDL_SetWindowInputFocus() function attempts to set the input focus to the specified window. However, it does not bring the window to the front.

This function might not be supported on all platforms and can sometimes fail silently, meaning it won't always work as expected.

Here's how you might use SDL_SetWindowInputFocus():

1SDL_Window* MyWindow{GameWindow.SDLWindow};
2SDL_SetWindowInputFocus(MyWindow);

While this function is supposed to give input focus to your window, it won't change the window's stacking order. This means your window could receive input focus but still be obscured by other windows.

Key Differences

• Visibility: SDL_RaiseWindow() makes the window visible and attempts to grab input focus. SDL_SetWindowInputFocus() only tries to set the input focus without altering the window's visibility.
• Platform Support: SDL_RaiseWindow() is generally more reliable across different platforms. SDL_SetWindowInputFocus() may not work on all platforms and can have no effect.
• Use Cases: Use SDL_RaiseWindow() when you need to ensure your window is visible and ready for interaction. Use SDL_SetWindowInputFocus() when you only need to change the input focus without altering the window's stacking order.

Example Usage

Here's an example demonstrating both functions in a practical context:

1#include <iostream>
2#include <SDL.h>
3#include <chrono>
4#include <thread>
5
6class Window {
7public:
8  Window() {
9    SDL_Init(SDL_INIT_VIDEO);
10
11    SDLWindow = SDL_CreateWindow(
12      "Example Window",
13      100, 100, 800, 600,
14      SDL_WINDOW_SHOWN
15    );
16  }
17
18  ~Window() {
19    SDL_DestroyWindow(SDLWindow);
20    SDL_Quit();
21  }
22
23  SDL_Window* SDLWindow{nullptr};
24};
25
26void HandleWindowEvent(SDL_WindowEvent& E) {
27  if (E.event == SDL_WINDOWEVENT_FOCUS_LOST) {
28    std::cout << "Window lost input focus\n";
29
30    using namespace std::chrono_literals;
31    std::this_thread::sleep_for(5s);
32
33    // Attempt to bring window to the front and focus it
34    SDL_RaiseWindow(SDL_GetWindowFromID(E.windowID));
35  }
36}
37
38int main(int argc, char** argv) {
39  Window GameWindow;
40  SDL_Event Event;
41
42  while (true) {
43    while (SDL_PollEvent(&Event)) {
44      if (Event.type == SDL_QUIT) {
45        return 0;
46      }
47      if (Event.type == SDL_WINDOWEVENT) {
48        HandleWindowEvent(Event.window);
49      }
50    }
51  }
52  
53  return 0;
54}

In this example, when the window loses input focus, SDL_RaiseWindow() is used to bring the window back to the front after a delay, ensuring the user can see it and interact with it.

1Window lost input focus

Choosing the right function depends on your application's needs and the behavior you want to achieve regarding window focus.