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  1. Path: sparky!uunet!zaphod.mps.ohio-state.edu!malgudi.oar.net!uoft02.utoledo.edu!desire.wright.edu!jmatthews
  2. Newsgroups: comp.sys.mac.programmer
  3. Subject: Re: LockPixels() before every CopyBits()?
  4. Message-ID: <1992Sep12.232233.4076@desire.wright.edu>
  5. From: jmatthews@desire.wright.edu
  6. Date: 12 Sep 92 23:22:33 EST
  7. References: <1992Sep11.213220.23039@alias.com>
  8. Organization: Wright State University 
  9. Lines: 31
  10.  
  11. > Assuming that the address is okay, I noticed that we don't call
  12. > LockPixels() before CopyBits().  After inserting calls to LockPixels()
  13. > and UnlockPixels(), it looks something like this:
  14. > 
  15. >     HLock((Handle) pixHandle1);
  16. >     HLock((Handle) pixHandle2);
  17. >     LockPixels(pixHandle1);
  18. >     LockPixels(pixHandle2);
  19. >     CopyBits((BitMap *)*pixHandle1, (BitMap *)*pixHandle2, ...);
  20. >     UnlockPixels(pixHandle2);
  21. >     UnlockPixels(pixHandle1);
  22. >     HUnlock((Handle) pixHandle2);
  23. >     HUnlock((Handle) pixHandle1);
  24. > 
  25. > Now this seems to be a bit much for every call to CopyBits.
  26.  
  27. LockPixels and UnlockPixels should be suffucient; the HLock and
  28. HUnlock aren't needed. I think you may need to be calling
  29. GetGWorldPixMap instead of getting the pixMap directly (except
  30. under ColorQD version 1.2 where it's broken (see the Q & A stack)).
  31.  
  32. IM VI just says use GetGWorldPixMap without much explanation. I've
  33. imagined this makes a difference with GWorlds on graphic accelerators
  34. or temporary memory, but I don't really know.
  35.  
  36. Any thoughts?
  37.  
  38. o----------------------------------------------------------------------------o
  39. | John B. Matthews, jmatthews@desire.wright.edu, disclaimer:= myViews <> WSU |
  40. |      "Whom the gods would destroy, they first invite to program in C"      |
  41. o----------------------------------------------------------------------------o
  42.