info-mac@uw-beaver (info-mac) (07/05/84)
From: Martin J Mahoney <UI.MJM%CU20B@COLUMBIA-20.ARPA> While using the Mac yesterday i discovered a bug in Quickdraw. I tried to draw two rectangles such that they shared a common side, however, one was drawn using the FRAMERECT quickdraw routine and the other used the LINETO quickdraw routines. When the two rectangles were drawn the one draw using the LINETO calls had its vertical sides slightly longer than the one drawn with the FRAMERECT call, when the sides should have all been the same length. Here is the code to reproduce the problem in both MS-basic and Forth: MS-BASIC 10 dim rect%(3) 20 rect%(0)=50:rect%(1)=50:rect%(2)=100:rect%(3)=100 30 call FRAMERECT(varptr(rect%(0))) 40 call moveto(0,50):call lineto(0,100) 50 call lineto(50,100):call lineto(50,50):call lineto(0,50) 60 end FORTH gint 50 50 100 100 frame rectangle 0 50 0 100 vector 0 100 50 100 vector 50 100 50 50 vector 50 50 0 50 vector Martin J. Mahoney -------
info-mac@uw-beaver (info-mac) (07/05/84)
From: Richard Reich <REICH@NYU-ACF1.ARPA> Sorry folks. That's bEhavior and hanging to the RIGHT and bewlow. BELOW UGH!! -r -------
info-mac@uw-beaver (info-mac) (07/05/84)
From: Richard Reich <REICH@NYU-ACF1.ARPA> The bahavior you describe is completely in accord with QD documentation and philosophy -- FrameRect draws "just inside" the argument rect. Remember that QD coords are at the interstices between pixels, not at the pixels themselves. Lines are drawn with the pen "hanging" to the left and BELOW the specified coords. No bug. -r -------