COleControl::GetDC
Provides for a windowless object to get a screen (or compatible) device context from its container.
CDC* GetDC(
LPCRECT lprcRect = NULL,
DWORD dwFlags = OLEDC_PAINTBKGND
);
Parameters
lprcRect
A pointer to the rectangle the windowless control wants to redraw, in client coordinates of the control. NULL means the full object's extent.dwFlags
Drawing attributes of the device context. Choices are:OLEDC_NODRAW Indicates that the object won't use the device context to perform any drawing but merely to get information about the display device. The container should simply pass the window's DC without further processing.
OLEDC_PAINTBKGND Requests that the container paint the background before returning the DC. An object should use this flag if it is requesting a DC for redrawing an area with transparent background.
OLEDC_OFFSCREEN Informs the container that the object wishes to render into an off-screen bitmap that should then be copied to the screen. An object should use this flag when the drawing operation it is about to perform generates a lot of flicker. The container is free to honor this request or not. However, if this flag is not set, the container must hand back an on-screen DC. This allows objects to perform direct screen operations such as showing a selection (via an XOR operation).
Return Value
Pointer to the display device context for the container CWnd client area if successful; otherwise, the return value is NULL. The display device context can be used in subsequent GDI functions to draw in the client area of the container's window.
Remarks
The ReleaseDC member function must be called to release the context after painting. When calling GetDC, objects pass the rectangle they wish to draw into in their own client coordinates. GetDC translates these to coordinates of the container client area. The object should not request a desired drawing rectangle larger than its own client area rectangle, the size of which can be retrieved with GetClientRect. This prevents objects from inadvertently drawing where they are not supposed to.
Requirements
Header: afxctl.h