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  enum FOCUS_EVENTS
  {
      FOCUS_LOST = 0,
      FOCUS_GOT = 1,
  };
 
  struct FOCUS_PARAMS
  {
      UINT      cmd;            // FOCUS_EVENTS
      HELEMENT  target;         // target element, for FOCUS_LOST it is a handle 
                                // of new focus element and for FOCUS_GOT it is 
                                // a handle of old focus element, can be NULL
      BOOL      by_mouse_click; // TRUE if focus is being set by mouse click
      BOOL      cancel;         // in FOCUS_LOST phase setting this field to TRUE
                                // will cancel transfer focus from old element 
                                // to the new one.
  };

Let's assume that some element A already has focus and another element B is getting focus. While setting focus engine sends FOCUS_LOST and FOCUS_GOT events in the following sequence:

First:

• Element that has focus before (A) will get FOCUS_LOST (and its parents will get FOCUS_LOST | SINKING).
• FOCUS_PARAMS.target in this event points to the new focus candidate element.
• FOCUS_PARAMS.cancel at this point can be set to TRUE to canel focus assignment.
• In this phase (FOCUS_LOST dispatching) HTMLayoutGetFocusElement(HWND hwnd, HELEMENT *phe) will return reference to old focus element (A).

Second:

• System will set internal variable “current_focus” to the new focus.
• After this point HTMLayoutGetFocusElement(HWND hwnd, HELEMENT *phe) will return new focus element (B).

Third:

• Element that is getting focus gets FOCUS_GOT (and its parents will get FOCUS_GOT | SINKING).
• FOCUS_PARAMS.target in this event points to the old focus element (A).
• FOCUS_PARAMS.cancel has no effect in this case.

Rationale:

While processing these events applications knows what element is loosing focus and what element is getting focus.