[Cuis-dev] Layout, belly dance

Juan Vuletich juan at jvuletich.org
Fri Oct 29 07:45:26 PDT 2021

On 10/29/2021 5:16 AM, Hilaire Fernandes via Cuis-dev wrote:
> Hi,
> When a window is dragged arround, its elements are doing a belly dance.
> Obverve this video: https://youtu.be/kn5qhPb-8DY
> Hilaire
> -- 
> GNU Dr. Geo
> http://drgeo.eu
> http://blog.drgeo.eu

This was not a bug in any of the morphic / graphics code, but a 
consequence of adopting the supposedly more "advanced" round-haf-to-even 
rule for Floats. See See 
https://en.wikipedia.org/wiki/Rounding#Round_half_to_even .

Fix was to add back the traditional rounding mode taught in school, as 
#roundHAFZ (round half way from zero, i.e. 0.5 -> 1), and use it for 
pixel coordinates, essentially for BitBlt.

Fix now at GitHub, with some tests both for Float and Fraction.


Juan Vuletich

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