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From: k36853p@saha.hut.fi (Tapani Otala)
Newsgroups: comp.sys.handhelds
Subject: HP48SX PICT quirk
Keywords: PICT,48SX
Message-ID: <1990Oct7.020606.6246@santra.uucp>
Date: 7 Oct 90 02:06:06 GMT
Sender: news@santra.uucp (Cnews - USENET news system)
Reply-To: k36853p@saha.hut.fi (Tapani Otala)
Organization: Helsinki University of Technology, Finland
Lines: 27


Anybody know the reason why this piece of code does not work properly:

	<< PICT RCL             @ save current PICT contents to stack
	   { #0 #0 } PVIEW	@ display PICT
	   .
	   .
	   .
	   PICT STO		@ restore old PICT contents from stack
	>>
	   
By 'not properly' I mean the garbage that fills the screen when HP
executes the 'PICT STO' stuff.  Looks to me like it (temporarily)
screws up the LCD display controller, i.e. makes it show incorrect area
of memory.  BTW, the garbage changes form, or the starting location
of it changes; anyway, sort of like looking at a continuous hex dump
of 0040:0000 of a PC...)

If this method of saving/restoring the PICT contents is incorrect,
better ideas anybody? (sure, PICT { #0 #0 } ROT REPL instead of PICT STO
restores it without the garbled display, but... its not that elegant)
What really bugs me is that the PIE demo program (pages 592-597 of
the Owner's Manual II) seems to use a similar trick, only without
the crap on screen.
  -- k36853p@saha.hut.fi  ! Clothes make the man. Naked people have little
    -- tpo@otax.tky.hut.fi  ! or no influence on society. -- Mark Twain
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