# flushBuffer() Copies the back buffer to the front buffer of the OpenGL context. ``` func flushBuffer() ``` ## Discussion If the receiver is not a double-buffered context, this call does nothing. If the [`NSOpenGLPixelFormat`](/documentation/AppKit/NSOpenGLPixelFormat) object used to create the context had a backing store attribute (`NSOpenGLPFABackingStore`), the buffers may be exchanged rather than copied. This is often the case in full-screen mode. According to the swap interval context attribute (see [`NSOpenGLCPSwapInterval`](/documentation/AppKit/NSOpenGLCPSwapInterval)), the copy may take place during the vertical retrace of the monitor, rather than immediately after [`flushBuffer()`](/documentation/AppKit/NSOpenGLContext/flushBuffer()) is called. An implicit `glFlush` is done by [`flushBuffer()`](/documentation/AppKit/NSOpenGLContext/flushBuffer()) before it returns. For optimal performance, an application should not call `glFlush` immediately before calling [`flushBuffer()`](/documentation/AppKit/NSOpenGLContext/flushBuffer()). Subsequent OpenGL commands can be issued immediately after calling [`flushBuffer()`](/documentation/AppKit/NSOpenGLContext/flushBuffer()), but are not executed until the buffer copy is completed. ## See Also [`func getValues(UnsafeMutablePointer, for: NSOpenGLContext.Parameter)`](/documentation/AppKit/NSOpenGLContext/getValues(_:for:)) Returns the value of the requested parameter. [`init?(format: NSOpenGLPixelFormat, share: NSOpenGLContext?)`](/documentation/AppKit/NSOpenGLContext/init(format:share:)) Returns an OpenGL context object initialized with the specified pixel format information. [`func setValues(UnsafePointer, for: NSOpenGLContext.Parameter)`](/documentation/AppKit/NSOpenGLContext/setValues(_:for:)) Sets the value of the specified parameter. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)