Re: gEDA-user: pcb, how to remove mm garbage (very short lines)?

[Stefan Salewski <mail@xxxxxxxxxxxx>]

Am Mittwoch, den 19.11.2008, 16:37 -0500 schrieb DJ Delorie:
> > Important may be the correct mapping of user input to internal pcb
> > coordinates.
> 
> The problem is rounding - some grid points round up, some round down.
> You end up with off-by-one bugs, no matter how "precise" you are,
> unless you can avoid the need to round completely.
> 

I see that rounding can be a problem.

I think that pcb program should always use its internal coordinates for
calculation and for its grid. If each user input (mouse click) is mapped
to this exact grid position (which is an integer multiple of pcbs
internal units) it may work. Of course, if user input is first mapped to
a mm grid, than rounded, rounding errors and problems may occur.

If user select i.e. 0.25 mm grid, pcb program should use a 0.01 mil
based grid which best fits a 0.25 mm look.

Maybe I am wrong, I do not no internals of pcb program, and have not
much experience in programming graphical software.

Best regards

Stefan




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