With this function you can get the internal Windows id value (the HWND, a pointer). This function is really only useful for extension writers who need the window handle to call Windows API's in DLL code (the returned pointer should be cast into a string and then in the C++ just cast it to an HWND). The table below shows the platforms supported along with what they return:
Platform Returns Windows Window HWND macOS NSWindow class Ubuntu (Linux) XWindow handle HTML5 Canvas ID
win_id = windows_handle();
The above code will store the game window id in a variable.