Path: utzoo!attcan!uunet!lll-winken!ncis.tis.llnl.gov!helios.ee.lbl.gov!pasteur!ucbvax!hoptoad!tim From: tim@hoptoad.uucp (Tim Maroney) Newsgroups: comp.sys.mac.programmer Subject: Re: Help: Using CopyBits for Update Message-ID: <7323@hoptoad.uucp> Date: 16 May 89 17:26:46 GMT References: <1617@neoucom.UUCP> <7254@hoptoad.uucp> <21931@santra.UUCP> <1203@speedy.mcnc.org> <7287@hoptoad.uucp> <21965@santra.UUCP> Reply-To: tim@hoptoad.UUCP (Tim Maroney) Organization: Eclectic Software, San Francisco Lines: 32 In article <21965@santra.UUCP> jmunkki@kampi.hut.fi (Juri Munkki) writes: >According to IM-I the whole string is drawn into an offscreen buffer >and only clipped after that. A complex clipping region will slow >down the copybits from this buffer to the screen. I still think you >don't loose any significant time. (Especially if you keep the screen >and your own offscreen bitmap aligned.) Is this still true in the Mac Plus and later ROMs? I doubt it. Like I said, I've seen that the contrary is true. If I have a terminal window open in TOPS Terminal and another window overlaps it, covering from some point right of the left margin all the way to the right margin, the lines go by significantly faster. Remember that one of the things they did in the Mac Plus ROMs was to speed up most QuickDraw operations. >It's somewhat easier to implement scrolling (or insert/delete) functions >if you keep an offscreen bitmap. Imagine that you have the calculator DA >in front of your terminal window. You update region after the operation >will most probably not be a rectangle. To update, you have to call DrawString >several times. QuickDraw will have to regenerate the mask from the region >every time you call DrawText. It only has to generate the mask once, when >you call copybits. Yes, I already said that this kind of update would be faster using an offscreen bitmap, and this may create an illusion of overall better speed to a naive user. That may be good enough, but for me, I prefer to work with the actual speed. And I still believe that overall, using an offscreen bitmap will be slower for every other operation. -- Tim Maroney, Consultant, Eclectic Software, sun!hoptoad!tim "Americans will buy anything, as long as it doesn't cross the thin line between cute and demonic." -- Ian Shoales