CreateWindow

2.x

The CreateWindow function creates an overlapped, pop-up, or child window. The CreateWindow function specifies the window class, window title, window style, and (optionally) the initial position and size of the window. The CreateWindow function also specifies the window's parent (if any) and menu.

Parameters

lpszClassName

Points to a null-terminated string specifying the window class. The class name can be any name registered with the RegisterClass function or any of the predefined control-class names. (See the following Comments section for a complete list.)

lpszWindowName

Points to a null-terminated string that represents the window name.

dwStyle

Specifies the style of window being created. This parameter can be a combination of the window styles and control styles given in the following Comments section.

x

Specifies the initial x-position of the window. For an overlapped or pop-up window, the x parameter is the initial x-coordinate of the window's upper-left corner, in screen coordinates. For a child window, x is the x-coordinate of the upper-left corner of the window in the client area of its parent window.

If this value is CW_USEDEFAULT, Windows selects the default position for the window's upper-left corner and ignores the y parameter. CW_USEDEFAULT is valid only for overlapped windows. If CW_USEDEFAULT is specified for a non-overlapped window, the x and y parameters are set to 0.

y

Specifies the initial y-position of the window. For an overlapped window, the y parameter is the initial y-coordinate of the window's upper-left corner. For a pop-up window, y is the y-coordinate, in screen coordinates, of the upper-left corner of the pop-up window. For list-box controls, y is the y-coordinate of the upper-left corner of the control's client area. For a child window, y is the y-coordinate of the upper-left corner of the child window. All of these coordinates are for the window, not the window's client area.

If an overlapped window is created with the WS_VISIBLE style and the x parameter set to CW_USEDEFAULT, Windows ignores the y parameter.

nWidth

Specifies the width, in device units, of the window. For overlapped windows, the nWidth parameter is either the window's width (in screen coordinates) or CW_USEDEFAULT. If nWidth is CW_USEDEFAULT, Windows selects a default width and height for the window (the default width extends from the initial x-position to the right edge of the screen, and the default height extends from the initial y-position to the top of the icon area). CW_USEDEFAULT is valid only for overlapped windows. If CW_USEDEFAULT is specified in nWidth for a non-overlapped window, nWidth and nHeight are set to 0.

nHeight

Specifies the height, in device units, of the window. For overlapped windows, the nHeight parameter is the window's height in screen coordinates. If the nWidth parameter is CW_USEDEFAULT, Windows ignores nHeight.

hwndParent

Identifies the parent or owner window of the window being created. A valid window handle must be supplied when creating a child window or an owned window. An owned window is an overlapped window that is destroyed when its owner window is destroyed, hidden when its owner is minimized, and that is always displayed on top of its owner window. For pop-up windows, a handle can be supplied but is not required. If the window does not have a parent window or is not owned by another window, the hwndParent parameter must be set to HWND_DESKTOP.

hmenu

Identifies a menu or a child window. This parameter's meaning depends on the window style. For overlapped or pop-up windows, the hmenu parameter identifies the menu to be used with the window. It can be NULL, if the class menu is to be used. For child windows, hmenu identifies the child window and is an integer value that is used by a dialog box control to notify its parent of events (such as the EN_HSCROLL message). The child window identifier is determined by the application and should be unique for all child windows with the same parent window.

hinst

Identifies the instance of the module to be associated with the window.

lpvParam

Points to a value that is passed to the window through the CREATESTRUCT structure referenced by the lParam parameter of the WM_CREATE message. If an application is calling CreateWindow to create a multiple document interface (MDI) client window, lpvParam must point to a CLIENTCREATESTRUCT structure. The CREATESTRUCT structure has the following form:

typedef struct tagCREATESTRUCT {    /* cs */
    void FAR* lpCreateParams;
    HINSTANCE hInstance;
    HMENU     hMenu;
    HWND      hwndParent;
    int       cy;
    int       cx;
    int       y;
    int       x;
    LONG      style;
    LPCSTR    lpszName;
    LPCSTR    lpszClass;
    DWORD     dwExStyle;
} CREATESTRUCT;

The CLIENTCREATESTRUCT structure has the following form:

typedef struct tagCLIENTCREATESTRUCT {  /* ccs */
    HANDLE  hWindowMenu;
    UINT    idFirstChild;
} CLIENTCREATESTRUCT;

For a full description of these two structures, see the Microsoft Windows Programmer's Reference, Volume 3.

Return Value

The return value is the handle of the new window if the function is successful. Otherwise, it is NULL.

Comments

For overlapped, pop-up, and child windows, the CreateWindow function sends WM_CREATE, WM_GETMINMAXINFO, and WM_NCCREATE messages to the window. If the WS_VISIBLE style is specified, CreateWindow sends the window all the messages required to activate and show the window.

If the window style specifies a title bar, the window title pointed to by the lpszWindowName parameter is displayed in the title bar. When using CreateWindow to create controls such as buttons, check boxes, and edit controls, use the lpszWindowName parameter to specify the text of the control.

Before returning, the CreateWindow function sends a WM_CREATE message to the window procedure.

Following are the predefined control classes an application can specify in the lpszClassName parameter:

Following are the window styles an application can specify in the dwStyle parameter.

Following are the button styles (in the BUTTON class) that an application can specify in the dwStyle parameter:

Following are the combo box styles (in the COMBOBOX class) that an application can specify in the dwStyle parameter:

Following are the edit control styles (in the EDIT class) that an application can specify in the dwStyle parameter:

Following are the list box styles (in the LISTBOX class) that an application can specify in the dwStyle parameter:

Following are the scroll bar styles (in the SCROLLBAR class) that an application can specify in the dwStyle parameter:

Following are the static control styles (in the STATIC class) that an application can specify in the dwStyle parameter. A static control can have only one of these styles.

Following are the dialog box styles an application can specify in the dwStyle parameter:

See Also

AnsiToOem, GetDialogBaseUnits, ShowWindow