Re: Double lowres graphics?

[Mike Pfaiffer <pfaiffer@mts.net>]

Dave Althoff Jr wrote:
> 
> Mike Pfaiffer (pfaiffer@mts.net) wrote:
> : Dennis Jenkins wrote:
<Question about double lores and a solution for Applesoft removed> 
> Mike is correct here.  Remember that the lo-res screen is implemented on
> the text screen.  You need an Apple ][e of Revision B or later, an Apple
> //c, or an Apple IIgs.  I'm not certain whether the Applesoft commands
> were added to the "unenhanced" ][e Applesoft or not...
> 
> (Dave goes and plays with his enhanced ][e)
> 
> Well, as it turns out, the double lo-res commands are NOT implemented in
> Applesoft on the ][e.  Can't check on the IIgs right now 'cause I'm using
> it to type this message.  8-)

	Hmmmm... I thought it was implemented on the enhanced //e and //c. I
know it is indeed implemented on the GS.

> But it is simple enough to use.  Here are the things you need to know:
> 
> 1)  You must have the 80-column display card active.
> 2)  To activate double graphics mode, you need to turn Annunciator #3 OFF.
>     Note that the supplement to the Extended 80-column card got this wrong
>     by saying that double graphics comes from turning Annunciator #3 ON; in
>     fact, that annunciator is left on by default; turning it off gives you
>     double graphics.
> 3)  The display is horizontally interlaced.  Even numbered columns
>     (0,2,4...78) are in auxiliary memory; odd numbered columns
>     (1,3,5...79) are in main memory.
> 4)  To distinguish between main and auxiliary screen memory, use the Page
>     1/Page 2 soft switch.  "Page 1" indicates main memory, "Page 2" indicates
>     auxiliary memory.  You can't see the second page of either text or
>     graphics when the 80-column card firmware is active.
> 
> To clear the entire double-lo-res screen and draw a white horizontal line
> across the middle of it, then, you would need to do the following:
> 
> ]PR#3
> ]GR
> ]POKE -16290,0: REM Annunciator 3
> ]POKE -16299,0: REM Page 2
> ]GR : REM Clear the other half of the page
> ]COLOR=15 : REM Set color=White
> ]HLIN 0,39 AT 24 : REM Draw line across even spaces
> ]POKE -16300,0 :REM Select main memory
> ]HLIN 0,39 AT 24 : REM Fill in the gaps
> 
> I have just been informed that the system is about to go down, so I have
> to run.  I'll present the list of soft-switches next time I read this
> newsgroup.

	It might be easier just to implement some routines in assembler. Just
remember it maps to the same area with the AUX page as the even columns
(0,2,4,etc.). The toughest thing to implement would be a line from one
point to another (not HLIN or VLIN). To implement a line the formula y=
mx + b should be useful.

				Later
				Mike




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