Toggling Fullscreen Mode in SDL2

SDL2 provides functions to easily switch between windowed and fullscreen modes for your application window. Here's how you can toggle fullscreen mode:

Step 1: Create a flag to keep track of the current window state:

1bool isFullscreen = false;

Step 2: When you want to toggle fullscreen mode (e.g., when a specific key is pressed), use the following code:

1if (isFullscreen) {
2    SDL_SetWindowFullscreen(window, 0);
3    isFullscreen = false;
4  } else {
5    SDL_SetWindowFullscreen(window,
6      SDL_WINDOW_FULLSCREEN_DESKTOP);
7    isFullscreen = true;
8  }

Here's a complete example that demonstrates toggling fullscreen mode when the 'F' key is pressed:

1#include <SDL.h>
2#include <SDL_image.h>
3#include <iostream>
4
5int main(int argc, char** argv) {
6  // Initialize SDL2 and create a window
7  SDL_Init(SDL_INIT_VIDEO);
8  SDL_Window* window = SDL_CreateWindow(
9    "Hello Window", 100, 100, 700, 300, 0);
10  bool isFullscreen = false;
11  bool quit = false;
12
13  while (!quit) {
14    SDL_Event event;
15    while (SDL_PollEvent(&event)) {
16      if (event.type == SDL_QUIT) {
17        quit = true;
18      } else if (event.type == SDL_KEYDOWN) {
19        if (event.key.keysym.sym == SDLK_f) {
20          if (isFullscreen) {
21            SDL_SetWindowFullscreen(window, 0);
22            isFullscreen = false;
23          } else {
24            SDL_SetWindowFullscreen(window,
25              SDL_WINDOW_FULLSCREEN_DESKTOP);
26            isFullscreen = true;
27          }
28        }
29      }
30    }
31
32    // Render your game content
33    // ...
34  }
35
36  // Cleanup and exit
37  // ...
38
39  return 0;
40}

In this example:

1. We create a flag isFullscreen to keep track of the current window state.
2. Inside the event loop, we check for the SDL_KEYDOWN event and specifically check if the 'F' key is pressed.
3. If the 'F' key is pressed, we toggle the fullscreen mode using SDL_SetWindowFullscreen:
   • If isFullscreen is true, we pass 0 to disable fullscreen mode.
   • If isFullscreen is false, we pass SDL_WINDOW_FULLSCREEN_DESKTOP to enable fullscreen mode.
4. We update the isFullscreen flag accordingly.

By using this approach, you can easily allow users to switch between windowed and fullscreen modes in your SDL2 application, providing a more immersive experience when desired.