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WM_ACTIVATE Overview Group

The WM_ACTIVATE message is sent when a window is being activated or deactivated. This message is sent first to the window procedure of the top-level window being deactivated; it is then sent to the window procedure of the top-level window being activated.

WM_ACTIVATE 

fActive = LOWORD(wParam);           // activation flag 

fMinimized = (BOOL) HIWORD(wParam); // minimized flag 

hwndPrevious = (HWND) lParam;       // window handle

Parameters

fActive

Value of the low-order word of wParam. Specifies whether the window is being activated or deactivated. This parameter can be one of the following values:

Value	Meaning
WA_ACTIVE	Activated by some method other than a mouse click (for example, by a call to the SetActiveWindow function or by use of the keyboard interface to select the window).
WA_CLICKACTIVE	Activated by a mouse click.
WA_INACTIVE	Deactivated.

fMinimized

Value of the high-order word of wParam. Specifies the minimized state of the window being activated or deactivated. A nonzero value indicates the window is minimized.

hwndPrevious

Value of lParam. Identifies the window being activated or deactivated, depending on the value of the fActive parameter. If the value of fActive is WA_INACTIVE, hwndPrevious is the handle of the window being activated. If the value of fActive is WA_ACTIVE or WA_CLICKACTIVE, hwndPrevious is the handle of the window being deactivated. This handle can be NULL.

Return Values

If an application processes this message, it should return zero.

Default Action

If the window is being activated and is not minimized, the DefWindowProc function sets the keyboard focus to the window.

Remarks

If the window is activated by a mouse click, it also receives a WM_MOUSEACTIVATE message.