Re: How to Develop New Features

[Hans Breuer <hans breuer org>]

At 07.09.2012 03:11, Matthew Rubenstein wrote:
>         Howdy. I'd like to code some revisions to Dia, but I haven't figured
> out how to get started, despite browsing around
> https://live.gnome.org/Dia and googling various programming keywords
> combined with "dia".
Checking out the code from master [1], building it and reading some of the 
existing code should be a good starting point.

>         I'd like to embed a library that would receive data as graph object
> labels are edited, compute against them, and return a value would be
> displayed in other graph object labels. Since it's an embedded library
> this seems like a plugin project, but I haven't found any documentation
> for APIs or otherwise for writing a Dia plugin.
There are a lot of plug-ins doing a multitude of things available with the 
Dia distribution. Just find one similar to your needs and start reading 
code. There also is some documentation about Dia concepts with the code. 
See $(dia)/doc and $(dia)/samples/Self for a start.

>         I'd also like to create a set of shapes that all work like the UML
> "Large Package" shape: implementing parenting.
I'm in the process of adding this facility to the custom shape mudule, so 
in the near future this can even be done with custom shapes written in XML.

> I'd also like to be able
> to toggle a parent between hiding and showing its children. If it works
> out I'd like to also click a parent to zoom it to fill the app viewport,
> then click a child that's itself a parent to zoom into it, and zoom back
> out. I haven't seen any docs for creating a new shape set,
http://dia-installer.de/doc/en/custom-shapes-chapter.html

> or how to add these dynamic behaviors to them.
The usual answer to more dynamic shape behaviour is writing objects in C.
See $(dia)/objects for a lot of examples. Toggling visibility of single 
objects would probably require some modification of the Dia core.

>         And I'd like to code the save/load code for a simple file format that
> stores objects with these behaviors. That seems like probably an export
> filter, but again I've found no docs to confirm it.
There are about two dozen export filters include with Dia. Please look at 
$(dia)/plug-ins for their implementations.

[1] http://git.gnome.org/browse/dia/

-------- Hans "at" Breuer "dot" Org -----------
Tell me what you need, and I'll tell you how to
get along without it.                -- Dilbert