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Win32 API Structures

This section details the structures used within the Win32 API. Structures are composite data types that group related data items, often of different types, into a single unit. They are fundamental for passing complex information to and from Win32 functions.

RECT

The RECT structure defines a rectangle by the coordinates of its upper-left and lower-right corners.

typedef struct _RECT {
    LONG left;
    LONG top;
    LONG right;
    LONG bottom;
} RECT;

• left: The x-coordinate of the rectangle's upper-left corner.
• top: The y-coordinate of the rectangle's upper-left corner.
• right: The x-coordinate of the rectangle's lower-right corner.
• bottom: The y-coordinate of the rectangle's lower-right corner.

See also: POINT, SIZE.

POINT

The POINT structure defines a point in two-dimensional space (x-coordinate and y-coordinate).

typedef struct _POINT {
    LONG x;
    LONG y;
} POINT;

• x: The horizontal coordinate.
• y: The vertical coordinate.

See also: RECT, SIZE.

SIZE

The SIZE structure specifies a Win32 application's size, in pixels, of a rectangle or a position, in the order cx (width) and cy (height).

typedef struct _SIZE {
    LONG cx;
    LONG cy;
} SIZE;

• cx: The width.
• cy: The height.

See also: POINT, RECT.

MSG

The MSG structure contains message information available from the application message queue.

typedef struct _MSG {
    HWND hwnd;
    UINT message;
    WPARAM wParam;
    LPARAM lParam;
    DWORD time;
    POINT pt;
} MSG;

• hwnd: Handle to the window that is to receive the message.
• message: Type of the message.
• wParam: Additional information about the message.
• lParam: Additional information about the message.
• time: Time at which the message was posted.
• pt: Cursor position, in screen coordinates, at the time the message was posted.

See also: WNDCLASS.

WNDCLASS

The WNDCLASS structure defines the window class characteristics that are registered by the RegisterClass function.

typedef struct _WNDCLASS {
    UINT style;
    WNDPROC lpfnWndProc;
    int cbClsExtra;
    int cbWndExtra;
    HINSTANCE hInstance;
    HICON hIcon;
    HCURSOR hCursor;
    HBRUSH hbrBackground;
    LPCTSTR lpszMenuName;
    LPCTSTR lpszClassName;
} WNDCLASS, *LPWNDCLASS;

• style: The storage class and extended styles for the class.
• lpfnWndProc: Pointer to the window procedure.
• cbClsExtra: Number of extra bytes required by class.
• cbWndExtra: Number of extra bytes required per window.
• hInstance: Handle to the instance of the application defining the window class.
• hIcon: Handle to the class icon.
• hCursor: Handle to the class cursor.
• hbrBackground: Handle to the class background brush.
• lpszMenuName: Pointer to a null-terminated string that specifies the resource name of the class menu.
• lpszClassName: Pointer to a null-terminated string that specifies the name of the window class.

See also: MSG, RegisterClass.

CREATESTRUCT

The CREATESTRUCT structure contains information about the window being created as a result of a CreateWindow or CreateWindowEx function call.

typedef struct _CREATESTRUCT {
        LPVOID lpCreateParams;
        HINSTANCE hInstance;
        HMENU hMenu;
        HWND hwndParent;
        int cx;
        int cy;
        int x;
        int y;
        LONG style;
        LPCTSTR lpszName;
        LPCTSTR lpszClass;
        DWORD dwExStyle;
} CREATESTRUCT, *LPCREATESTRUCT;

• lpCreateParams: Pointer to the value specified in the lpCreateParams parameter of the CreateWindowEx function.
• hInstance: Handle to the module creating the window.
• hMenu: Handle to the menu of the window.
• hwndParent: Handle to the owner window or creator.
• cx: Width of the window.
• cy: Height of the window.
• x: Horizontal position of the window.
• y: Vertical position of the window.
• style: Window styles.
• lpszName: Pointer to the window name.
• lpszClass: Pointer to the window class name.
• dwExStyle: Extended window styles.

BITMAP

The BITMAP structure specifies the bitmap characteristics. It is used by the GetObject function.

typedef struct tagBITMAP {
    LONG bmType;
    LONG bmWidth;
    LONG bmHeight;
    LONG bmWidthBytes;
    WORD bmPlanes;
    WORD bmBitsPixel;
    LPVOID bmBits;
} BITMAP, *PBITMAP, NEAR *NBMPTR, FAR *LPBITMAP;

• bmType: Specifies the bitmap type.
• bmWidth: Specifies the bitmap width in bits.
• bmHeight: Specifies the bitmap height in raster lines.
• bmWidthBytes: Specifies the size, in bytes, of each scan line in the bitmap.
• bmPlanes: Specifies the number of color planes.
• bmBitsPixel: Specifies the number of bits used to define each color index.
• bmBits: Pointer to the bitmap memory.

LOGFONT

The LOGFONT structure contains the characteristics of a logical font—that is, the specification for a font that can be used to create a font with the graphics programming interface (GDI).

typedef struct tagLOGFONT {
    LONG lfHeight;
    LONG lfWidth;
    LONG lfEscapement;
    LONG lfOrientation;
    LONG lfWeight;
    BYTE lfItalic;
    BYTE lfUnderline;
    BYTE lfStrikeOut;
    BYTE lfCharSet;
    BYTE lfOutPrecision;
    BYTE lfClipPrecision;
    BYTE lfQuality;
    BYTE lfPitchAndFamily;
    TCHAR lfFaceName[LF_FACESIZE];
} LOGFONT;

This structure has many members controlling font properties such as height, width, escapement, orientation, weight, italic, underline, strikeout, character set, precision, quality, and face name.

SECURITY_ATTRIBUTES

The SECURITY_ATTRIBUTES structure contains security descriptor information that is used when creating certain securable objects.

typedef struct _SECURITY_ATTRIBUTES {
    DWORD nLength;
    LPVOID lpSecurityDescriptor;
    BOOL bInheritHandle;
} SECURITY_ATTRIBUTES, *PSECURITY_ATTRIBUTES, *LPSECURITY_ATTRIBUTES;

• nLength: Size of this structure in bytes.
• lpSecurityDescriptor: Pointer to a SECURITY_DESCRIPTOR structure that specifies the security of the object.
• bInheritHandle: Specifies whether the handle can be inherited by child processes.

FILETIME

The FILETIME structure is a 64-bit value that represents the number of 100-nanosecond intervals since January 1, 1601 (UTC).

typedef struct _FILETIME {
    DWORD dwLowDateTime;
    DWORD dwHighDateTime;
} FILETIME, *PFILETIME, *LPFILETIME;

• dwLowDateTime: Specifies the low-order part of the file time.
• dwHighDateTime: Specifies the high-order part of the file time.

For a comprehensive list of Win32 API structures, please refer to the main index or use the search functionality.