Techwiki:Win32k/BASEOBJECT

The GDI Base Object, which is a header at the top of every GDI Object. The structure is called BASEOBJECT and is defined as follows for Windows XP, Windows 2003 and Vista, same for 64 Bit Versions:

typedef struct _BASEOBJECT
{
     HANDLE hHmgr;
     ULONG ulShareCount;
     USHORT cExclusiveLock;
     USHORT BaseFlags;
     PW32THREAD Tid;
} BASEOBJECT, *POBJ; 

typedef struct _BASEOBJECT DD_BASEOBJECT, *PDD_BASEOBJECT; (correct?)

The pointer to a _BASEOBJECT is known as a POBJ.

BaseFlags

0x800 for objects that are allocated from a lookaside list (DC, region, bitmap, palette, font and brush)