Buttons_editing.c

uiDefIDPoinBut(block, 0, ID_OB, B_CHANGEDEP, "Ob: ", lx, (cy-=19), 220,19, &wmd->objectcenter, "Parent Object for hook, also recalculates and clears offset");

DNA_Modifier_types.h

typedef struct WaveModifierData {
	ModifierData modifier;
	
	struct Object *objectcenter;
        
	short flag,pad;

	float startx, starty, height, width;
	float narrow, speed, damp, pad1;
	
	float timeoffs, lifetime,pad2;
} WaveModifierData;