Window Management API Reference

This section details the Windows API functions and structures used for creating, manipulating, and managing windows within the Windows operating system. Effective window management is crucial for building responsive and user-friendly graphical applications.

Core Window Functions

`CreateWindowEx`

HWND CreateWindowEx( DWORD dwExStyle, LPCTSTR lpClassName, LPCTSTR lpWindowName, DWORD dwStyle, int x, int y, int nWidth, int nHeight, HWND hWndParent, HMENU hMenu, HINSTANCE hInstance, LPVOID lpParam );

Creates an overlapping, pop-up, or child window. This is the primary function for creating windows.

Parameters:

dwExStyle: Extended window styles.
lpClassName: The name of the window class.
lpWindowName: The text of the window.
dwStyle: Window styles.
x: The horizontal position of the window.
y: The vertical 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 window-creation data.

Returns: If the function succeeds, the return value is a handle to the new window. Otherwise, it is NULL.

`DestroyWindow`

BOOL DestroyWindow(HWND hWnd);

Destroys the specified window. The function sends a WM_DESTROY message to the window to be destroyed prior to destroying the window.

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

`ShowWindow`

BOOL ShowWindow(HWND hWnd, int nCmdShow);

Sets the visibility of the specified window. The `nCmdShow` parameter controls how the window is shown.

Parameters:

hWnd: Handle to the window.
nCmdShow: Controls the way the window is to be shown. Common values include SW_SHOW, SW_HIDE, SW_MINIMIZE, SW_MAXIMIZE.

Returns: If the window was previously visible, the return value is nonzero. Otherwise, the return value is zero.

Window Information and State

`GetWindowText`

int GetWindowText(HWND hWnd, LPTSTR lpString, int nMaxCount);

Copies the text of the specified window's title bar (if it has one) into a buffer.

Returns: The length, in characters, of the copied string, not including the null terminator.

`SetWindowPos`

BOOL SetWindowPos( HWND hWnd, HWND hWndInsertAfter, int X, int Y, int cx, int cy, UINT uFlags );

Changes the size, position, and ordering of a child, pop-up, or top-level window. It can also change the Z-order.

Use the SWP_NOMOVE and SWP_NOSIZE flags to preserve the current position or size.

`IsWindowVisible`

BOOL IsWindowVisible(HWND hWnd);

Determines whether the specified window, its parent window, its parent's parent, and so on, are visible.

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

Window Messages and Notifications

Window management heavily relies on the Windows message loop. Applications receive notifications and commands by processing messages sent to their windows.

Common Window Messages

WM_CREATE: Sent when a window is first created.
WM_DESTROY: Sent to a window when it is being destroyed.
WM_SIZE: Sent when the size, either initial or after the window has been resized, of a client area of a window has changed.
WM_MOVE: Sent after the window moves.
WM_PAINT: Sent when the system or another application requires that a window be redrawn.
WM_COMMAND: Sent to a window when the user selects a menu item; when a control in a child window sends a notification message to its parent window; or when an accelerator key is used.

Understanding message processing is fundamental to Windows programming. Familiarize yourself with the DefWindowProc function, which handles messages that your application does not explicitly process.

Structures Used in Window Management

Structure	Description
`WNDCLASS`	Defines the window class attributes that are registered by the `RegisterClass` function.
`CREATESTRUCT`	Contains information about the window being created that is passed to the window's creation function.
`RECT`	Defines a rectangle using the coordinates of its upper-left and lower-right corners.

Continue exploring the API Reference for more Windows development topics.