[etoys-dev] x-y plane questions

[Ricardo Moran]

On Sun, Mar 18, 2012 at 10:12 AM, Steve Thomas <sthomas1 at gosargon.com>wrote:

> Scott,
>
> I started looking at the code and was able to change the tick mark width's
> for the number lines and playing with the marksWidth/marksHeight.
> Part of the issue I was having was that the GraphPaper's line width was 1,
> but the mark's with was 2, so there was no way to center them.
> See samples below:
> [image: Inline image 1]
>
> But I couldn't figure out how to change the pixel width of the graph
> paper, could you point me in the right direction, thanks.
> Also any hints on how can I set the rotational center of the number line
> to its "0" point?  I can do it with Etoys tiles, But need hints on where
> would I modify the code and figure out the zero point.
>

Hi Steve,

I think you can change the rotation center to its 0 point by evaluating
this:

For horizontal number lines:

> self rotationCenter: ((self left + self offset + (0 - minValue *
> pixelsPerUnit)) @ (self top + self marksHeight)) - self topLeft / self
> extent * 1.0


For vertical number lines:

> self rotationCenter: (self left + self legendsWidth) @ (self bottom - self
> offset - (0 - minValue * pixelsPerUnit)) - self topLeft / self extent * 1.0


To keep it updated this would have to be hooked up everywhere the number
line can change its size. And (maybe) something should be done in case the
0 point is not visible.

Cheers,
Richo


> Thanks,
> Stephen
>
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>
>
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