SDL_GetWindowWMInfo

The window manager’s own handles for this window, as a hash reference, or undef when SDL will not say.

my $wm = SDL_GetWindowWMInfo($win) or die SDL_GetError();
printf "%s display=%#x window=%#x\n", $wm->{driver}, $wm->{display}, $wm->{window};

subsystem is the numeric SDL_SYSWM_* value and driver is the same lowercase name SDL_GetCurrentVideoDriver uses. The remaining keys are the ones that windowing system has: display and window under X11, display and surface under Wayland - as plain integers, because they are C pointers and XIDs, not anything Perl can follow.

This is what a graphics API that is not OpenGL needs in order to draw on an SDL window: Peta::WebGPU creates its surface from exactly these two handles.