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From "Andrew C. Oliver" <acoli...@apache.org>
Subject Re: Excel charts
Date Fri, 09 Jan 2004 01:22:15 GMT

> From: Dimitri Pissarenko <dimitri.pissarenko@gmx.net>
> Reply-To: "POI Users List" <poi-user@jakarta.apache.org>
> Date: Thu, 08 Jan 2004 21:31:13 +0100
> To: "POI Users List" <poi-user@jakarta.apache.org>
> Cc: gerhard.goerlich@gmx.net
> Subject: Re: Excel charts
> Hello!
> Since many of us are
> 1) interested in Excel charts
> 2) busy

Yeah, who isn't

> I think that it would make sense to collect some ideas about making
> the first step towards a functioning Excel charts implementation
> before starting to code.
> So, in my opinion, we could discuss following issues:
> 1) Architecture
> Should this first attempt of POI-powered Excel charts be a clean
> solution (carefully designed and tested) or a quick and dirty
> solution?
> Pro clean solution: avoidance of hard to find errors
> Pro quick and dirty solution: flexibility - we know little about Excel
> chart format and should have the highest possible experimentation
> freedom

Architecture is a smile on a dog.  Learn the records, learn the "grammar",
follow the existing examples, you're not the first to implement something
new so do what they did and refractor later.  Most importantly of all...
Write unit tests.  

> 2) How to start
> We could write and publish a short overview over the coarse structure
> of this Excel chart interface. I mean, we (by "we" I mean POI users,
> not developers) should get at least a rough idea about how this Excel
> interface should work.
> This short overview could help us.

No, first you learn the structure.  After that it practically writes itself.

> 3) What chart types to implement first?

The simplest ones first.  I think bar was the simplest IIRC, but I haven't
looked in a while.
> 4) Make it bi-directional or uni-directional?
> Should the first prototype of the Excel chart interface just write the
> charts or read and write them?

Whatever, the "gold" prototype should do round trip (that¹s what it takes
for us to call it production ready).
> For my personal purpose, write-only solution is sufficient.

You can do that and as long as you get the unit tests and prove it works
we'll commit it and call it "alpha" code.
> 5) How to avoid hidden hindrances?
> I assume that other people attempted to implement Excel chart
> interface in the past. Since there is no such interface now, it is
> logical to assume that there were some serious difficulties in
> implementing it.

Time and documentation.  Both are in great shortage.  The latter exacerbates
the former.
> What were these difficulties?

Chart records are a "delta" against a known-only-to-excel super-graph.  Most
of these records are completely undocumented.

> How can we avoid them now?

Time and effort.  Lots of unit tests!
> If someone of those pioneers is reading this message, please tell us
> your experiences and recommendations.

Junit, Junit, Junit!

> Best regards
> dap

Andrew C. Oliver
Custom enhancements and Commercial Implementation for Jakarta POI

For Java and Excel, Got POI?

The views expressed in this email are those of the author and are almost
definitely not shared by the Apache Software Foundation, its board or its
general membership.  In fact they probably most definitively disagree with
everything espoused in the above email.

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