On Thu, Nov 3, 2016 at 3:45 PM, Stirling Westrup <swest...@gmail.com> wrote:
> I've noticed that the transformation matrices that this function builds > for rotated screens is not quite correct. > > In particular, it consistently builds maps from 0 to width or height > instead of from 0 to width-1 or height-1. > > This means that an inverted screen maps (0,0) to (width,height) instead of > (width-1,height-1). This causes out-of-boundary errors when mapping screens. > > OMG. I just worked out that this is a *DELIBERATE* error in order to accommodate the half-open-interval method of describing rectangles. The transforms as created work for half-open boundaries, but then fail to work for mapping individual pixels. If the code were fixed to correctly handle pixel coordinates, all of the boundary calculations in X would be off by one... -- Stirling Westrup Programmer, Entrepreneur. https://www.linkedin.com/e/fpf/77228 http://www.linkedin.com/in/swestrup http://technaut.livejournal.com http://sourceforge.net/users/stirlingwestrup
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