ldo@waikato.ac.nz (Lawrence D'Oliveiro, Waikato University) (06/14/91)
Anybody remember the classic QuickDraw clipping problem? What happens is you record a sequence of drawing calls with OpenPicture/ClosePicture, and you find that the resulting picture disappears if you draw it at any origin other than (0,0). The problem arises because the default clipping region in the grafPort is the rectangle (-32767,-32767,32767,32767), so if you do any translation of the resulting picture, the clipping boundaries immediately overflow and wrap around, giving you an empty clipping region! This bit me again today, in a particularly memorable way: I'd created a picture on my machine, which displayed fine once I'd got it into Word, but disappeared when viewed on a colleague's machine. As soon as I saw the output from DeRez, I knew what the problem was; I fixed it by changing the bounds of the clipping region to +/-8192. My machine is a vintage II running System 7.0; the other machine is an SE running 6.0.7. What I'm curious about is: when was the problem fixed? Was it in Color QuickDraw (i e my ROM), 32-bit QuickDraw (pre-7.0), or System 7.0? Yours, the inveterate trivia collector... Lawrence D'Oliveiro fone: +64-71-562-889 Computer Services Dept fax: +64-71-384-066 University of Waikato electric mail: ldo@waikato.ac.nz Hamilton, New Zealand 37^ 47' 26" S, 175^ 19' 7" E, GMT+12:00 To someone with a hammer and a screwdriver, every problem looks like a nail with threads.