You can use a CExtControlBar-derived class which implements the following virtual method:
virtual void OnControlBarPositionChange(
CExtControlBar * pBarEventSrc,
e_control_bar_position_changing_t eCBPC,
bool bInitial,
bool bFinal
);
This method is invoked when the control bar is resized and redocked. The
eCBPC parameter defines how the position of the control bar changes. The
e_control_bar_position_changing_t enumeration is defined in scope of the
CExtControlBar class:
enum e_control_bar_position_changing_t
{
__ECBPC_EMPTY = 0,
__ECBPC_REDOCKING = 1,
__ECBPC_ROW_RESIZING = 2,
__ECBPC_IN_ROW_RESIZING = 3,
__ECBPC_FLOATING_FRAME_RESIZING = 4,
__ECBPC_MUTUAL_DEPENDENCY = 5,
};