nameWindow name used as its persistent ID and displayed title; ### can separate the title from the ID.
p_openOptional open state in Uint8Array[0]. Write only 0 (closed) or 1 (open); the close button writes 0. Null omits the close button. The native call accesses this writable backing memory directly.
flagsImGuiWindowFlags options controlling this operation; combine compatible flag bits with |.
True when this scope is open/active and its contents may be submitted. Call EndPopup() only when true; on false, skip both contents and the matching end.
Begin appending to an open modal popup.