CreateCaret

The CreateCaret function creates a new shape for the system caret and assigns ownership of the caret to the specified window. The caret shape can be a line, a block, or a bitmap.

BOOL CreateCaret(

HWND hWnd,	// handle to owner window
HBITMAP hBitmap,	// handle to bitmap for caret shape
int nWidth,	// caret width
int nHeight	// caret height
);

Parameters

hWnd

Identifies the window that owns the caret.

hBitmap

Identifies the bitmap that defines the caret shape. If this parameter is NULL, the caret is solid. If this parameter is (HBITMAP) 1, the caret is gray. If this parameter is a bitmap handle, the caret is the specified bitmap. The bitmap handle must have been created by the CreateBitmap, CreateDIBitmap, or LoadBitmap function.

If hBitmap is a bitmap handle, CreateCaret ignores the nWidth and nHeight parameters; the bitmap defines its own width and height.

nWidth

Specifies the width of the caret in logical units. If this parameter is zero, the width is set to the system-defined window border width. If hBitmap is a bitmap handle, CreateCaret ignores this parameter.

nHeight

Specifies the height, in logical units, of the caret. If this parameter is zero, the height is set to the system-defined window border height. If hBitmap is a bitmap handle, CreateCaret ignores this parameter.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

The nWidth and nHeight parameters specify the caret's width and height, in logical units; the exact width and height, in pixels, depend on the window's mapping mode.

CreateCaret automatically destroys the previous caret shape, if any, regardless of the window that owns the caret. The caret is hidden until the application calls the ShowCaret function to make the caret visible.

The caret is a shared resource; there is only one caret in the system. A window should create a caret only when it has the keyboard focus or is active. The window should destroy the caret before losing the keyboard focus or becoming inactive.

You can retrieve the width or height of the system's window border by using the GetSystemMetrics function, specifying the SM_CXBORDER and SM_CYBORDER values. Using the window border width or height guarantees that the caret will be visible on a high-resolution screen.

See Also

CreateBitmap, CreateDIBitmap, DestroyCaret, GetSystemMetrics, HideCaret, LoadBitmap, ShowCaret

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