CS_SAVEBITS top-level constant
int
const CS_SAVEBITS
Saves, as a bitmap, the portion of the screen image obscured by a window of this class. When the window is removed, the system uses the saved bitmap to restore the screen image, including other windows that were obscured. Therefore, the system does not send WM_PAINT messages to windows that were obscured if the memory used by the bitmap has not been discarded and if other screen actions have not invalidated the stored image.
Implementation
const CS_SAVEBITS = 0x0800;