[Kstars-devel] RFC: Redesing of KStars

[Thomas Kabelmann]

Hi Jason,


> I imagine there will be quite a few problems with libkdeedu, especially
> extdate (which is basically a hacked version of QDateTime and friends).
> Q_EXPORT is just a macro that was defined in Qt-3.x, to indicate that the
> function should be exported.  Try changing them to KDE_EXPORT maybe?
seems to compile with KDE_EXPORT, but there are a lot of other compile errors 
too, so I will have a look at QT4 porting guide and try to change them.

I have refined the design of my approach to refactor the skymap and data 
classes. I will use the composite design pattern, so we can organize the sky 
recursively.

We will have 2 abstract classes - SkyComponent and SkyComposite. A 
SkyComponent is a simple object which knows, how to draw, update and init 
(init will data from files too) itself, for example the equator. A 
SkyComposite is a complex object like solar system, which is composited by 
other components or composites and delegates draw/update/init to it's 
components. It could be also possible that Composite is initializing it's 
components by itself. This is useful for the StarComposite (currently 
starList), because it would make no sense having a data file for each star, 
but this are imlemenation details.

The components of a composite will be added in the constructor. The solar 
system could look like this:

SolarSystem::SolarSystem()
{
	add(new Sun());
	add(new Merkur());
	...
	add(new Pluto());
}

A draw of a composite would look like this:
SkyComposite::draw(Skymap *map)
{
	foreach (component in components) // components is a list of components
		component->draw(map);
}

With this design, we just add a SkyMapComposite as member to the KStars class, 
which will recursively add new components/composites. An object hierarchy 
would look like this:

- SkyMapComposite
	- SolarSystemComposite
		- Sun
		...
		- Merkur
	- StarComposite
		- a lot of stars
	- DeepSkyObjectComposite
		a lot of objects
	- equator
	...
	- horizon

We just have to say skyMapComponent->update()/draw()/init() and all objects do 
it at once.

For further explanation I've appended a class diagram for the redesign. If 
there are any questions, please feel free to ask me. If the explanation was 
to short I would write a design paper, too.

Thomas