SetForegroundWindow

SetForegroundWindow is a Windows API function in user32.dll that attempts to bring a specified window to the foreground and give it focus. It is commonly used to ensure a particular window becomes the active window in response to user action or program logic.

The function signature is: BOOL SetForegroundWindow(HWND hWnd); The hWnd parameter is a handle to the top-level window to be activated and brought to the foreground. If the call succeeds, the window becomes the foreground window and typically receives input focus.

Behavior and limitations: Windows enforces focus-stealing protections to prevent background processes from forcibly taking the foreground. As a result, SetForegroundWindow may fail for handles from non-foreground processes or when the user has not recently interacted with the application. In such cases the function returns zero, and extended error information can be retrieved with GetLastError. When successful, the window is activated, and depending on its state, it may be restored or brought to the front in the z-order.

Error handling and related functions: If SetForegroundWindow fails, examining GetLastError can help determine the cause, such as ERROR_ACCESS_DENIED or an invalid handle. To allow other processes to set the foreground window, applications can use AllowSetForegroundWindow. Other related functions include BringWindowToTop (which changes z-order without necessarily activating the window), ShowWindow (to adjust visibility and state), SetActiveWindow, and AttachThreadInput (to synchronize input queues between threads in some scenarios).

Usage considerations: SetForegroundWindow should be used in response to explicit user actions or well-defined program logic, acknowledging Windows focus rules. Relying on it for silent focus changes can lead to a poor user experience or focus-related failures.