kicad-developers team mailing list archive

[Wayne Stambaugh <stambaughw@xxxxxxxxx>]

Even though I'm not quite ready to start discussing the new file formats
just yet, here a few of my thoughts on inheritance:

Inheritance will be implemented in a second phase during the development
of the new file formats and possibly pushed into the version 7 release.
The reason is that there is currently no support for inheritance in the
schematic object code so that would have to be written first.

Existing symbol libraries would be converted as flat symbols (no
inheritance).  I'm not interested in trying to write code to analyze
existing symbol libraries and try to map them to a coherent inheritance
model.  It would be too much work for too little gain.  Only new symbol
libraries could be created using inheritance.

Inheritance would make for cleaner symbol libraries but not so much for
the schematic object code.  It may turn out the inheritance concept is
not worth the effort it takes to implement it and we abandon the idea.
Nothing is set it stone at the moment.

Inherited symbols would have to be flattened before they could be
embedded into the schematic file.  Otherwise, modifying an inherited
symbol would change all of the inherited symbols in a schematic which
may not be what the user expects or wants.  Having to flatten inherited
symbols is a potential argument for not implementing them.

I expect the implementation of the new schematic file formats to be a
bumpy ride.  We are making a fundamental paradigm shift (embedding
symbols in schematic files), adding a lot of new functionality (gate/pin
swapping, netclasses, etc.) and changing the internal units to metric.
I don't think the for one second that the new schematic file formats are
going to be a slam dunk.  On the contrary, I think it's going to be more
difficult than the effort required to rewrite the footprint and board
file formats.  Those of use who were around for that remember just how
much work was involved.

Cheers,

Wayne

On 7/16/2018 10:28 AM, Rene Pöschl wrote:
> My guess would be maintainability.
> Having some way of sharing parts of different symbols with each other
> makes it way easier to manage large libs. (Nobody would be forced to use
> these features but they can make live easier for library maintainers. We
> could then for example provide a single nmos graphic that is then used
> in all nmos symbols of the official lib. Reducing the work for both
> contributors and maintainers.)
> 
> On 16/07/18 16:24, Tomasz Wlostowski wrote:
>> On 16/07/18 16:04, Jeff Young wrote:
>>> Thinking more about it, we could probably auto-convert existing
>>> aliases to inheritance when we read them in.
>> Why do we need any inheritance at all? My only guess is to make Kicad
>> even more hackerish and difficult to understand.
>>
>> Tom
>>
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