How do I check if a platform supports opacity before using `SDL_SetWindowOpacity()`?

Question

Ryan McCombe · Accepted Answer

You can determine whether a platform supports opacity by testing the return value of SDL_SetWindowOpacity() or SDL_GetWindowOpacity(). If these functions fail, the platform or the specific window likely does not support opacity. Here's an example:

Example: Checking Opacity Support

Here's an example where we test if the platform we're running on supports opacity:

1#include <SDL.h>
2#include <iostream>
3
4int main() {
5  if (SDL_Init(SDL_INIT_VIDEO) < 0) {
6    std::cerr << "SDL Init Error: "
7      << SDL_GetError() << "\n";
8    return -1;
9  }
10
11  SDL_Window* window = SDL_CreateWindow(
12    "Opacity Check",
13    SDL_WINDOWPOS_CENTERED,
14    SDL_WINDOWPOS_CENTERED,
15    400, 200, 0
16  );
17
18  if (!window) {
19    std::cerr << "Window Creation Error: "
20      << SDL_GetError() << "\n";
21    SDL_Quit();
22    return -1;
23  }
24
25  if (SDL_SetWindowOpacity(window, 0.5f) < 0) {
26    std::cerr << "Opacity Not Supported: "
27      << SDL_GetError() << "\n";
28  } else {
29    std::cout << "Opacity Supported!\n";
30  }
31
32  SDL_DestroyWindow(window);
33  SDL_Quit();
34  return 0;
35}

1Opacity Not Supported: That operation is not supported

Testing is essential for writing cross-platform code that gracefully handles unsupported features.

Window Opacity

Checking Opacity Support

Example: Checking Opacity Support

Window Opacity

Game Development with SDL2

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