const xwin::State& state = xwin::getXWinState();
#if defined(XWIN_WINDOWS)
HINSTANCE hinstance = state.hinstance;
HWND hwnd = window->hwnd;
#endif
On MacOS, CrossWindow creates an NSApplication in its MacOS specific main function, and a pointer to this is accessible from xwin::getXWinState().
The NSApplication is used to create NSWindow and NSView objects, with Views inside of Windows on MacOS.
A xwin::MacOSWindow object is accessible by grabbing a window's delegate:
const xwin::State& state = xwin::getXWinState();
#if defined(XWIN_MACOS)
NSApplication app = state.application;
NSWindow* window = window->window;
NSView* view = window->view;
#endif