Porting to Carbon, Lock/UnlockPortBits and Lock/UnlockPixels

Question

I am porting an OS 9 app to Carbon and then Mac OS X.
In the original source, I might have something like:
GetGWorld (&currPort,&currDev);
SetGWorld (mGridPictGW->gw, nil);
LockPixels ((mGridPictGW->gw)->portPixMap);
// do some drawing here
SetGWorld (currPort,currDev);
UnlockPixels ((mGridPictGW->gw)->portPixMap);
The LockPixels() and UnlockPixels() calls are now causing compiler errors (CW) for
"illegal use of incomplete struct/union/class 'OpaqueGrafPtr'"
I know, from reading the porting docs, that I need to handle this
with the new ACCESSORS, but my question is about the new function
Lock/UnlockPortBits(). It says in the docs that "this is not a
replacement for Lock/UnlockPixels()". So do I need to use both
of them? Do I now need to rewrite the above code to look like this?
GetGWorld (&currPort,&currDev);
SetGWorld (mGridPictGW->gw, nil);
LockPortBits(mGridPictGW->gw);
LockPixels(GetPortPixMap(mGridPictGW->gw));
// do some drawing here
SetGWorld (currPort,currDev);
UnlockPixels ((mGridPictGW->gw)->portPixMap);
UnockPortBits(mGridPictGW->gw);
Or do I use this new function instead of Lock/Unlock Pixels? Or is
this new function not even needed here, and I simply need to rewrite
the Lock/UnlockPixels() calls as shown, using the GetPortPixMap() accessor?
Thanks for any advice.
Stephen
G4 Dual 800 QuickSilver / PBook G4 Titanium   Mac OS X (10.3.9)  

Answer 1

If you're drawing from a GWorld to a window, you don't need to call LockPortBits(). QuickDraw does the lock for you. Call Lock/UnlockPortBits() only when you need to directly access a Mac OS X window's back buffer.
  Mac OS X (10.4)