CS_PARENTDC top-level constant
Sets the clipping rectangle of the child window to that of the parent window so that the child can draw on the parent. A window with the CS_PARENTDC style bit receives a regular device context from the system's cache of device contexts. It does not give the child the parent's device context or device context settings. Specifying CS_PARENTDC enhances an application's performance.
const CS_PARENTDC = 0x0080;