Re: A86: Efficiency Problem Part III

To: assembly-86@lists.ticalc.org
Subject: Re: A86: Efficiency Problem Part III
From: ZeromusMog@aol.com
Date: Tue, 15 Dec 1998 20:19:32 EST
Delivered-To: assembly-86-outgoing@towerguard.unix.edu.sollentuna.se
Reply-To: assembly-86@lists.ticalc.org


In a message dated 15/12/98 12:03:19 Pacific Standard Time, ComAsYuAre@aol.com
writes:

<< > There must be an easier way... is there a way to inverse a portion of the
 >  screen?
 
 
 sure.  screen memory starts at $fc00 and goes until $ffff.  just do this to
 invert the byte at hl:
 	ld a,(hl)
 	cpl			;one's complement
 	ld (hl),a
 
 you can do this in a loop for inverting a bunch of lines:
 	ld hl,$fc00
 	ld b,16*7		;7 lines, 16 bytes each
 invert_loop:
 	ld a,(hl)
 	cpl
 	ld (hl),a
 	inc hl
 	djnz invert_loop
 	ret >>

Yes, but letters are smaller than one byte wide. I don't really know how to do
stuff that complicated yet... if I was inverting across the screen, I could do
it. However, it starts on the third character and the end depends on the menu
on the screen. Also, I am inverting only ONE line, not seven. It's very
similar to the menu at the beginning of Star Chaser.

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