display capture issue

I have an app which captures a display (CGDisplayCapture or CGDisplayCaptureWithOptions), grabs its drawing context, and then draw image on it:

//1.  capture
auto cpErr = CGDisplayCaptureWithOptions( mDid, kCGCaptureNoOptions );
  if ( cpErr != kCGErrorSuccess )
  {
    LOGEX( "😂 Failed to capture Display, ID:%d", mDId );
    return;
  }
// Grab context
context = CGDisplayGetDrawingContext( mDId );

//Draw image
CGContextDrawImage( context, rect, image );
CGContextFlush( context );

The video is pretty good, but two issues:

1. When captured, according to the document, it only capture the event on that display, actually, when the app running, all system key event (i.g. Shift+Cmd+R) and swipe won't work.

2. CGContextDrawImage is taking pretty high CPU usage, in my Mac mini 2018, it is taking over 20%

Anyone got the solution to the above issues?

-Thanks :)