The handle to a display device context for the specified window indicates success.

NULL indicates that no display device context is available.

To get extended error information, call GetLastError.

The following code example shows a window procedure that processes a WM_PAINTmessage by using BeginPaintto prepare a window for painting, and then draws an icon or bitmap in the window.

Note:
To make the following code example easier to read, error checking is not included. Do not use this code example in a release configuration unless you have modified it to include secure error handling.

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#include <windows.h> HICON ghIcon = NULL; HBITMAP ghbmMask = NULL; HBITMAP ghbmColor = NULL; LRESULT APIENTRY MainWndProc( HWND hWnd, // window handle UINT message, // type of message WPARAM wParam, // additional information LPARAM lParam) // additional information { switch (message) { case WM_PAINT: PAINTSTRUCT ps; HDC hdc; COLORREF crTxt, crBk; hdc = BeginPaint(hWnd, &ps); if (ghIcon) DrawIcon(hdc, 10, 10, ghIcon); if (ghbmMask) DrawBitmap(hdc, 10, 50, ghbmMask); if (ghbmColor) DrawBitmap(hdc, 50, 10, ghbmColor); EndPaint(hWnd, &ps); break; // Include case statements for other messages here. default: // Pass the message on if unproccessed. return (DefWindowProc(hWnd, message, wParam, lParam)); } return (0L); }

The BeginPaintfunction sets the clipping region of the device context to exclude any area outside the update region.

The update region is set by the InvalidateRectfunction and by the system after sizing, moving, creating, scrolling, or any other operation that affects the client area.

If the update region is marked for erasing, BeginPaintsends a WM_ERASEBKGNDmessage to the window.

An application should not call BeginPaintexcept in response to a WM_PAINT message.

Each call to BeginPaintmust have a corresponding call to the EndPaintfunction.

If the caret is in the area to be painted, BeginPainthides the caret to prevent it from being erased.

If the window's class has a background brush, BeginPaintuses that brush to erase the background of the update region before returning.