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Re: Internal units in the KiCAD source code


Hi Johannes,

Thank you for your suggestion but the internal units for each format
were chosen for a specific reason.  There really is no justifiable
reason to change them as they have been carefully selected based on the
requirements of the objects they represent.  Conversion code is provided
for each internal unit so plotting to standard units such as
millimeters, inches, etc is trivial.  I'm not opposed to adding support
for changing the plot units.  I am opposed to changing the internal units.



On 2/13/20 9:32 AM, Johannes Pfister wrote:
> The KiCAD code uses all kinds of different units for distances.
> Amongst other things I found:
>   nm: pcbnew internal units
>   10nm: Gerbview internal units
>   100nm EEschema internal units
>   1um: PL-Editor internal units
>   0.1mil (2.54um): SetViewport
>   1mil (25.4 um): WS_DRAW_ITEM_BASE and GetSizeMils
> And the native File formats use mm (pcbnew) and mil (EEschema).
> Something like SVG exports in 0.1 mil steps. I think that this is not
> very consistent and something like a PLOTTER class needs to handle
> different IU-sizes.
> My idea is to rewrite the internal units so that nm are used
> everywhere inside the source code, and only parts that write or read
> files and display data to or read data from the user should convert it
> to another unit system. I don't want to change any file formats.
> That would make it a bit more straightforward, more consistent, metric
> and an SVG-Plotter would use a metric step size. The disadvantage
> would be that there would be an about 2m or 4m limit in every
> direction, assuming int is 32 bit, which is AFAIK true for all
> platforms KiCAD current supports.
> Before i rewrite code, can you say what you guys think about it?
> Johannes Pfister
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