On Jun 27, 2011, at 1:13 PM, Jens Alfke wrote:

> It makes sense to me. Integer coordinates denote the grid lines between 
> pixels, not the pixel centers. Likewise, the hot-spot of the cursor is in 
> between pixels, not in the center of a pixel. In the case of the default 
> arrow cursor, the hot-spot is at the tip of the arrow.
> 
> Put that together, and what you get is that if the tip pixel of the arrow 
> cursor is positioned over the bottom pixel of the view, the hot-spot is 
> actually at y=1.0.
> 
> This may seem a little unexpected, but I don’t think most programmers ever 
> worry about it. Hit-testing shouldn’t require single-pixel accuracy anyway, 
> so I doubt the user would notice if your calculations were a pixel off.


This seems like a correct interpretation. Thanks for the insight.

--Richard

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