CreateCaret function (winuser.h)

Article
05/07/2024

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.

Syntax

BOOL CreateCaret(
  [in]           HWND    hWnd,
  [in, optional] HBITMAP hBitmap,
  [in]           int     nWidth,
  [in]           int     nHeight
);

Parameters

[in] hWnd

Type: HWND

A handle to the window that owns the caret.

[in, optional] hBitmap

Type: HBITMAP

A handle to 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. The caret is drawn to the screen via the XOR operation.

If hBitmap is a bitmap handle, CreateCaret ignores the nWidth and nHeight parameters; the bitmap defines its own width and height. The application should not delete the hBitmap until the caret is destroyed or replaced by another caret.

[in] nWidth

Type: int

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.

[in] nHeight

Type: int

The height of the caret, in logical units. 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 value

Type: BOOL

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 system provides one caret per queue. 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.

DPI Virtualization

This API does not participate in DPI virtualization. The width and height parameters are interpreted as logical sizes in terms of the window in question. The calling thread is not taken into consideration.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	winuser.h (include Windows.h)
Library	User32.lib
DLL	User32.dll
API set	ext-ms-win-ntuser-caret-l1-1-0 (introduced in Windows 8)

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