Displaying a Cursor - Win32 Programmer's Reference

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Displaying a Cursor

Windows automatically displays the class cursor (the cursor associated with the window to which the cursor is pointing). You can assign a class cursor while registering a window class. The following example illustrates this by assigning a cursor handle to the hCursor member of the WNDCLASS structure identified by the wc parameter.

WNDCLASS wc;

// Fill the window class structure with parameters that

// describe the main window.

wc.style = NULL; // class style(s)

wc.lpfnWndProc = (WNDPROC) MainWndProc; // window procedure

wc.cbClsExtra = 0; // no per-class extra data

wc.cbWndExtra = 0; // no per-window extra data

wc.hInstance = hinst; // app that owns the class

wc.hIcon = LoadIcon(NULL, IDI_APPLICATION); // class icon

wc.hCursor = LoadCursor(hinst, MAKEINTRESOURCE(230)); // class cursor

wc.hbrBackground = GetStockObject(WHITE_BRUSH); // class background

wc.lpszMenuName = "GenericMenu"; // class menu

wc.lpszClassName = "GenericWClass" // class name

// Register the window class.

return RegisterClass(&wc);

When the window class is registered, the cursor identified by 230 in the application's resource-definition file will be the default cursor for all windows based on the class.

Your application can change the design of the cursor by using the SetCursor function and specifying a different cursor handle. However, when the cursor moves, Windows redraws the class cursor at the new location. To prevent the class cursor from being redrawn, you must process the WM_SETCURSOR message. Each time the cursor moves and mouse input is not captured, Windows sends this message to the window in which the cursor is moving.

You can specify different cursors for different conditions while processing WM_SETCURSOR. For example, the following example shows how to display the hCurs3 cursor whenever the cursor moves over the icon of a minimized application.

case WM_SETCURSOR:

// If the window is minimized, draw the hCurs3 cursor.

// If the window is not minimized, draw the default

// cursor (class cursor).

if (IsIconic(hwnd))

{

SetCursor(hCurs3);

break;

}

When the window is not minimized, Windows displays the class cursor.

You can replace a class cursor by using the SetClassLong function. This function changes the default window settings for all windows of a given class. The following example replaces the existing class cursor with the hCurs2 cursor.

// Change the cursor for window class represented by hwnd.

SetClassLong(hwnd, // window handle

GCL_HCURSOR, // change cursor

(LONG) hCurs2); // new cursor

For more information, see Window Classes and Mouse Input.

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