J.COOK@ENS.Prime.COM (03/16/90)
Variable QuickDraw Performance? I don't understand. QuickDraw seems to give different levels of performance depending upon when it is invoked for a flying line application. I don't see why it is happening. Take the "Flying Line" program from the "Macintosh Programming Primer" by Mark & Reed. Basically, this program blanks the screen and then draws five lines. It draws the lines in XOR mode. The first line is drawn by picking two random endpoints and drawing a line between them. Succeeeding lines are drawn by applying a delta-x and delta-y to each endpoint to arrive at a new pair of endpoints to draw a line between. Once five lines are up, the algorithm "loops" by erasing the oldest line by redrawing it in XOR mode and drawing a new line based on the newest line. In this manner, you have a set of five lines flying about the screen. The program works, however, when it is run, it may run at speed "x" or at speed "2x". I would even claim there is a speed "4x". There is no predicting. This is all observed by eye. So, the question is: Why? I've tried two different machines. The first is an 8Mb II with a Radius 1152 x 882 with a Radius QuickColor Graphics Accelerator both on and off. A moderate number (< 6) CDEVs/Inits and Apple- talk are present. The second machine was an 8Mb IIx with a standard Apple 13" RGB monitor driven by a RasterOps 264 card, no printer, no external devices, no Appletalk, and practially no CDEVs/Inits other than that shipped by Apple. In all cases, the expected combinations were tried: 1-bit, 8-bit, 32-bit graphics mode, Multifinder on/off, Appletalk/inits/cdevs/external devices removed, if possible. Nothing seemed to be the key. Any ideas? My only thought is that the slowdown is due to a task tied to the VBL, but why would it sometimes affect things and not others? The presense or absense of a SystemTask() call does not make a difference. This obviously is not a critical problem, but I am really curious. Thanks if you know, Jim Cook J.COOK@ENS.PRIME.COM (Note: Mail to me may bounce this weekend while our network is being reconfigured). Disclaimer: "Just my confusion, not Prime's".