Path: utzoo!attcan!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!decwrl!purdue!ames!xanth!mcnc!kk From: kk@mcnc.org (Krzysztof Kozminski) Newsgroups: comp.sys.mac.programmer Subject: Re: Help: Using CopyBits for Update Message-ID: <1203@speedy.mcnc.org> Date: 12 May 89 16:17:42 GMT References: <1617@neoucom.UUCP> <7254@hoptoad.uucp> <21931@santra.UUCP> Reply-To: kk@mcnc.org.UUCP (Krzysztof Kozminski) Organization: Microelectronics Center of NC; RTP, NC Lines: 15 In article <21931@santra.UUCP> jmunkki@kampi.hut.fi (Juri Munkki) writes: >In article <7254@hoptoad.uucp> tim@hoptoad.UUCP (Tim Maroney) writes: >>Maybe I'm being dense, but what is the advantage to keeping an >>offscreen bitmap in a terminal emulator and using it for updates? > >I had a very good reason why using the offscreen bitmap might be even faster >than drawing directly (in some special cases), but I can't remember it right >now. I'll post the reasoning, if I remember it again. How about this: sometimes the visible and/or clipping regions on the screen are not rectangular => drawing to the screen is slower than drawing to an offscreen *rectangular* PixMap due to the extra effort necessary for the proper clipping of each object drawn. KK