kicad-developers team mailing list archive

[Tomasz Wlostowski <tomasz.wlostowski@xxxxxxx>]

On 13.01.2015 20:11, Wayne Stambaugh wrote:
> This is a tricky issue that has been discussed before.  The general
> consensus in the past has been not to support forward compatibility.  It
> increases maintenance and complexity of the file parser for a minimal
> net gain to the user.  My preference is to force users that want to
> bleed on the edge to use nightly builds rather than try to maintain any
> forward file compatibility.  

Hi Wayne,

The only argument I see for limited forward compatibility is when
someone uses a bleeding edge build to benefit from the latest features
(or just adds them them as needed), but must be able to share the design
(read only is OK) with other people who are forced to stick to the
stable version (think of corporate/university users where software is
centrally managed by some IT department).

> I also don't like idea of creating special tokens just for version
> compatibility.  I would like to keep the file format as readable as
> possible.  My guess is that any version compatibility tokens will have
> to reference the other objects in the file making the file less readable
> which is something that I will be reluctant to support.

I didn't consider impact on file readability. I'm not the type who edits
graphics with a text editor (and a PCB, after all is mostly a graphical
design), so as long as the file structure is easy to figure out, I'm OK
with it. I understand your point though and I'm not going to argue here
(especially given the fact that you've put quite a lot of effort to make
the format readable).

> 
> How do you plan to prevent data loss when editing newer files with older
> versions of pcbnew? 



> One solution might be to ignore any unsupported tokens and warn the user
> that there may (will?) be data loss if the board is modified and saved.
> Even this solution I think has a lot of potential pitfalls.  Make newer
> files read only is also a possibility.
> 
> The only way I would support forward file compatibility is if there is:
> 
> a) no loss of file readability
> b) no loss of user data
> d) no unnecessary increase in the complexity of the file parser code.
> c) no hoard of angry users who want to edit a new file version with and
> older version of pcbnew.

OK, how about this:
- No extra version tokens (fits point A)
- Warning instead of error on unrecognized tokens (point C - no big
changes needed in the parser)
- If the opened file is produced by a newer version of Kicad, issue a
big warning when the user attempts to save it, that certain features
will be lost (points B and D - if somebody complains we can always tell
him he was warned). AFAIK this is what most commercial software does.

Cheers,
Tom