[Insight-developers] Developer's Guide - Write A Filter

[Will Schroeder]

Hi Luis-

Thank you so much for looking this over.


At 07:43 AM 9/29/2001 -0400, Luis Ibanez wrote:

>1) In "overview of filter creation" it says that GenerateData()
>    has to allocate memory for the output, while ThreadedGenerateData()
>    should not. Is that right ?
>    I thought that the streaming mechanism was doing the allocations
>    before calling GenerateData()... (I'm not allocating memory in
>    most of the filters...maybe we just found a bug  :-) )

If ThreadedGenerateData() is implemented by the filter writer (and not 
GenerateData()), then the default implementation of GenerateData() 
allocates memory, and then invokes the filter's ThreadedGenerateData(). If 
you have written a GenerateData() without memory allocation, then that 
needs to be fixed.


>2) I added some figures from a tutorial we have here, they illustrate
>    the pipeline connections (ProcesObject/DataObject), and a UML
>    sequence diagram of the updating mechanism. The original figures
>    were done with xfig, and exported as eps.
>
>    Probably we will have to modify these figures to better fit the
>    text.

Thanks, I assume these figures are checked in.


>3) I would like to add some UML class diagrams to make clearer what
>    the options are when selecting the base class for a filter. This
>    is discussed in "Overview of Filter creation". In particular
>    showing the method that the developer will have to override.

Okay.


>4) A UML sequence diagram could also be helpful for describing the
>    update negotiation at the DataObject level.
>
>5) It could probably be good to add a table (or some kind of symbol
>    in the text) to indicate what methods are expected to be overrided
>    by the user and what methods are  provided by the system.
>    The discussion on the updating mechanism is nicely detailed, but
>    I guess that the developer reading it will have in mind the
>    question: "what do I have to rewrite ?"

We can create a table, good idea.


>6) It was great to add the description of the relation between
>    Multithreading and the Events. I finally understood why the
>    multithreaded filters are keeping track of the thread id
>    before invoking events.

Simultaneous IO from threads is bad.


>7) A description of the Command/Observers/Event mechanism seem
>    to be necesary. Would you prefer to make of this a separte
>    chapter ?
>    We have a couple of diagrams on this too.

I think that this belongs in the UsersGuide. Let's revisit the organization 
of the guides next week and make sure they still make sense.



>Document style
>
>1) The formating is now using the InsightDocument style, and we have
>    the decoration lines from fancyhdr.sty   :)

If this doesn't do the trick, I'm going to reinstall my MikTex. I found 
that it does have those style files, but only if you do the full 
installation, which is a huge monster to download.


>2) fancyhdr.sty and floatflt.sty were checked in under
>    InsightDocumens/Latex
>
>3) would you like to use a different font (maybe courier) for class
>    names and method names cited in the text ?
>    we have some macros that can facilitate that.

I have done this in the past (in some books I have helped write). The 
feedback I've received is that all the font changes are very hard on the 
eye. So I look to use difference clues to indicate what's a method 
(trailing () like Modified()) and class names (leading itk::ClassNameHere).


>4) we are including the itk logo in each documen, so the itkLogo.jpg
>    file is repeated in different directories. Should we arrange a
>    central directory for graphic files ? like is done in
>    Insight/Documentation/Art ?

I think that's the right place Luis. Can you create the directory and put 
the file in there?

Thanks,
Will