Window Management Functions

The Win32 API provides a rich set of functions for managing windows, user interface elements, and handling user input. This section covers core functionalities for creating, manipulating, and interacting with windows.

Core Window Functions

Function	Description
CreateWindowEx	Creates an overlapped, pop-up, or child window with a wide style.
DestroyWindow	Destroys the specified window. The DestroyWindow function posts a WM_DESTROY message to the window to which the specified handle identifies.
ShowWindow	Sets the show state of a window.
UpdateWindow	Updates the client area of a window that has been interrupted.
GetMessage	Retrieves messages from the calling thread's message queue.
DispatchMessage	Dispatches a message to a window procedure.

CreateWindowEx

Syntax

HWND CreateWindowExA(
  DWORD     dwExStyle,
  LPCSTR    lpClassName,
  LPCSTR    lpWindowName,
  DWORD     dwStyle,
  int       X,
  int       Y,
  int       nWidth,
  int       nHeight,
  HWND      hWndParent,
  HMENU     hMenu,
  HINSTANCE hInstance,
  LPVOID    lpParam
);

Creates an overlapped, pop-up, or child window with a wide style.

Parameters

• dwExStyle: Extended window styles.
• lpClassName: The registered class name.
• lpWindowName: The window name.
• dwStyle: Window styles.
• X: The initial position of the window.
• Y: The initial position of the window.
• nWidth: The width of the window.
• nHeight: The height of the window.
• hWndParent: Handle to the parent window.
• hMenu: Handle to a menu, or a child-window identifier.
• hInstance: Handle to the application instance.
• lpParam: Pointer to values for object creation.

Return Value

• If the function succeeds, the return value is a handle to the newly created window.
• If the function fails, the return value is NULL.

DestroyWindow

Syntax

BOOL DestroyWindow(
  HWND hWnd
);

Destroys the specified window. The DestroyWindow function posts a WM_DESTROY message to the window to which the specified handle identifies.

Parameters

• hWnd: Handle to the window to be destroyed.

Return Value

• If the function succeeds, the return value is nonzero.
• If the function fails, the return value is zero.

ShowWindow

Syntax

BOOL ShowWindow(
  HWND hWnd,
  int  nCmdShow
);

Sets the show state of a window.

Parameters

• hWnd: Handle to the window.
• nCmdShow: Controls the way the window is to be shown.

Return Value

• If the window was previously visible, the return value is nonzero.
• If the window was previously invisible, the return value is zero.

UpdateWindow

Syntax

BOOL UpdateWindow(
  HWND hWnd
);

Updates the client area of a window that has been interrupted.

Parameters

• hWnd: Handle to the window to be updated.

Return Value

• If the function succeeds, the return value is nonzero.
• If the function fails, the return value is zero.

GetMessage

Syntax

BOOL GetMessageA(
  LPMSG lpMsg,
  HWND  hWnd,
  UINT  wMsgFilterMin,
  UINT  wMsgFilterMax
);

Retrieves messages from the calling thread's message queue.

Parameters

• lpMsg: Pointer to a MSG structure that receives message information.
• hWnd: Handle to the window whose messages are to be retrieved.
• wMsgFilterMin: Minimum message value.
• wMsgFilterMax: Maximum message value.

Return Value

• If the function retrieves a message other than WM_QUIT, the return value is nonzero.
• If the function retrieves the WM_QUIT message, the return value is zero.
• If there is an error, the return value is -1.

DispatchMessage

Syntax

LRESULT DispatchMessageA(
  const MSG *lpMsg
);

Dispatches a message to a window procedure.

Parameters

• lpMsg: Pointer to a structure that contains the message to be dispatched.

Return Value

• The return value is the result of the message processing and depends on the message sent.