This is a handle to the OS’s native window that X-Plane is running in. This dataref is only safe for 32-bit builds of X-Plane; use sim/operation/windows/system_window_64 to get a 64-bit native window handle.
You should almost never need to use this dataref!
Contents X-Plane 6.70 -> 10.10
Macintosh: this dataref is a Carbon WindowRef.
Windows: This is a Window HWND.
Linux: This is an X11 XID for a Window object. (TODO: unclear when this first became available, as Linux was not a supported OS for 6.70)
Contents X-Plane 10.20 and Newer, 32-bit builds
Macintosh: this returns NULL; the underlying Cocoa window is not available.
Windows: This is a Window HWND.
Linux: This is an X11 XID for a Window object.
Contents X-Plane 10.20 and Newer, 64-bit builds
Macintosh: this returns NULL; the underlying Cocoa window is not available.
Windows: This is the low 32 bits of a Window HWND.
Linux: This is the low 32 bits of an X11 XID for a Window object.