Re: A89: Re: Re: Survey for the next version of PlusShell
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Re: A89: Re: Re: Survey for the next version of PlusShell
What do you say about my idea to move tha screen a bit in the graph-mem, and
then get rid of the need for clipping at _all_ sides
//Olle
Dux Gregis wrote:
>
> >>
> >>At 20:46 1998-11-18 -0500, you wrote:
> >>>On the 89 LCD, a sprite must be clipped only when it crosses the top or
> >left
> >>>side LCD edges.
> >>
> >>Not really true... a sprite on the top row, with a negative x value
> >>(x=-8,y=0) would in that case start writing before the video memory
> >>starts... so a special case is needed with such sprites.
> >
> >That's what I meant: the two special cases are at the top and left side of
> >the screen. It's also a good idea to not put the sprite when it is
> >completely off the screen in either of the other two directions, although
> >that would not really constitute clipping.
>
> Let me revise that: there are actually three cases, the third being that
> _both_ coordinates are of negative values. In some clipping routines, this
> must be treated as a unique case. (Really; before I implemented that case
> in the 89 clipping routine I wrote, it actually crashed the calc when you
> tried to move the sprite off both the top and the left edges of the screen
> simultaneously) This is very nice because on all other TI calcs there are
> eight cases you must implement! (or at least test)
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