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Re: Re: Metric and English grids sizes.
Dick Hollenbeck <dick@...>
Mon, 12 Oct 2009 15:52:40 -0500
Thunderbird 22.214.171.124 (X11/20090817)
jean-pierre charras - INPG wrote:
Dick Hollenbeck a écrit :
--- In kicad-devel@ yahoogroups. com
<mailto:kicad-devel%40yahoogroups.com>, Dick Hollenbeck <dick@...> wrote:
What about the 'obvious' solution, i.e. just saving the grid size in
Then we need something more stable. I'd switch over to a 0 based index
into the list of grid sizes, but maybe treat user size as special,
assigning it -1, just so it does not get moved in the future if more
sizes are added.
decimils like all the other things in pcbnew?
GridSize 1000 1000
for a 100mil grid...
A lookup on the dozen or so predefined values is not so heavy (and
anyway is only done on load)
This is obvious, and quite agreeable. I'd like to have a grid offset in
there too. See next posting.
Unfortunately, grid size cannot be handled in decimils.
In pcbnew grid is handled as double.
This is because for many grids values in mm, using a value rounded in
decimils creates a cummulative error that can be important
(some mm for a 300 mm board)
So grid sizes must be given
- always in inches or decimils but using a floating point value, for non
integer values as needed for metric grids
- or as an integer in decimils or um units and give the used unit (um ou
decimil) as parameter
If I understand your concern then Jean-Pierre, we can use Lorenzo's
concept but just have to provide enough information in the file. If we
are going to support a true "metric only" grid mode, then providing the
engineering units in the file is a way to remember both the mode and the
interpretation of the magnitude.
Along with the grid offset :)