Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!mips!apple!dlyons
From: dlyons@Apple.COM (David A Lyons)
Newsgroups: comp.sys.apple2
Subject: Re: help optimizing asm routine (and help with GetCaretTime)
Message-ID: <53391@apple.Apple.COM>
Date: 28 May 91 09:43:34 GMT
References: <3638@kluge.fiu.edu>
Organization: Apple Computer Inc., Cupertino, CA
Lines: 49

In article <3638@kluge.fiu.edu> acmfiu@serss0.fiu.edu (ACMFIU) writes:
>because i'm not using TextEdit for my program, i need to blink the insertion
>cursor. everytime through my main event loop ('event_loop' below), i call
>'blink_cursor' which accomplishes this. however, it doesn't blink the cursor
>at all

By the way (regarding a different message):  If you're not getting null
events, it's because you are getting an Update event which you are not
handling.  Window update events are not stored in the event queue--
if there is no higher-priority event, the system looks through all the
windows front-to-back until it finds one with a non-empty update region.
If you don't handle that by calling BeginUpdate, blahblahblah, EndUpdate,
(which has the side-effect of emptying out the update region) then you'll
get the same event again.

I didn't examine your code closely enough to diagnose the real problem,
but I did notice it barfs when the tick count value wraps around past
zero (which happens every 2.2 years of continuous use)! -- I suggest a
slightly simpler approach, using only the low word of the tick count,
and also working properly when it wraps around past zero:

  pha
  pha
  _GetTick
  pla
  plx                   ;ignore high word
  tay                   ;keep copy of low word in Y
  sec
  sbc previous_ticks
  cmp blink_internal    ;set earlier from GetCaretTime
  bcc dont_blink_it
  sty previous_ticks
  ...                   ;blink the thing, with InvertRect or whatever
dont_blink_it

Note that the calculation (Now - Previous) gives you a legitimate number
of ticks even if it's something like $0005 minus $FFF0.  That's $0015.

(If you do "loop until current-ticks is greater-than-or-equal-to previous
ticks plus increment" you can get stuck with "loop until X >= $FFFE", and
X will go right past the big value back into the small values, if your
main loop takes a significant amount of time per iteration.)
-- 
David A. Lyons, Apple Computer, Inc.      |   DAL Systems
Apple II System Software Engineer         |   P.O. Box 875
America Online: Dave Lyons                |   Cupertino, CA 95015-0875
GEnie:DAVE.LYONS  CompuServe:72177,3233 Internet:dlyons@apple.com

My opinions are my own, not Apple's.