Run SDL Window (Centurion GUI lib) in other thread? - c++

Question

I want to run a window in another thread (ie not the main thread) using Centurion (which uses SDL).
Here is how i run the thread:
auto _THR_WIN_HWND_MAINLOOP = ([&HWND_instance]() {
HWND_instance._mainloop_();
});
// starts the window thread.
std::thread _thr(_THR_WIN_HWND_MAINLOOP);
_thr.detach();
Then my _mainloop_() function:
const cen::sdl sdl;
// main loop here.
cen::window hwnd;
cen::renderer renderer = hwnd.make_renderer();
hwnd.show();
cen::event_handler handler;
while (__flag_open) {
while (handler.poll()) {
if (handler.is<cen::quit_event>()) {
__flag_open = false;
break;
}
}
renderer.clear_with(cen::colors::white);
renderer.fill_rect(cen::frect{ 25.0, 500.0, 125.0, 75.0 });
renderer.present();
}
Just a note, the cen::window constructor calls SDL_Init().
The problem is is that on the off chance i run my program, it closes after a second or so. if i JOIN the thread instead of detaching it the window stays open. However i need the window to run in the background as i have other code that must be run. Is there any way to have a background thread that fully handles the SDL window as if it was its own program?
NOTE: No errors are thrown, the window just closes after a second or so, on the off chance?!

Answer 1

It turns out i was not labeling my HWND_instance class variable as static, and that variable held almost everything to do with SDL. So when it got destroyed, so did the SDL instances:
before:
_CE_WINDOW_HWND HWND_instance(s.get()); // create the instance.
auto _THR_WIN_HWND_MAINLOOP = ([&]() {
HWND_instance._mainloop_();
});
// starts the window thread.
std::thread _thr(_THR_WIN_HWND_MAINLOOP);
_thr.detach();
After:
static _CE_WINDOW_HWND HWND_instance(s.get()); // create the instance.
auto _THR_WIN_HWND_MAINLOOP = ([&]() {
HWND_instance._mainloop_();
});
// starts the window thread.
std::thread _thr(_THR_WIN_HWND_MAINLOOP);
_thr.detach();
As you can see, now the variable does not get destroyed after the function ends, preserving the lifetime of SDL and the class.