[Thuban-devel] Re: RfD: Support for layer specific resources

[Martin Schulze]

Bernhard Herzog wrote:
> >> >> > And for Thuban.UI.classifier:
> >> >> >
> >> >> > add_properties_dialog(Layer, Classifier)
> >> >> > add_properties_dialog(RasterLayer, Classifier)
> >> >
> >> > I'm not sure how I am supposed to implement this since
> >> > classifier.py doesn't import mainwindow and I don't know if it
> >> > would be a good idea to do so.
> >> 
> >> You could put that code into Thuban.UI.mainwindow which already depends
> >> on Thuban.UI.classifier because it currently refers to the dialogs in
> >> there directly.  That would keep the module dependencies the same as
> >> now.
> >
> > Err???
> 
> Now it's me going Err :)

*sigh*

> >  Are you really sure you want this code appear in mainwindow.py?
> 
> No, I'm not sure, and I don't have the time to find the perfect place
> for it.  You didn't want it in Thuban.UI.classifier, though, and that

No, I wasn't sure how I am supposed to implement this in
classifier.py.  I'm fine adding it there.  In fact, on July 27th I
proposed to add this to classifier.py.

> was what I was replying to.  classifier does not depend on mainwindow
> but would if you put the add_properties_dialog call there.  That's how I
> understood your reply anyway.  My suggestion, then, was that, since
> mainwindow currently depends on classifier, you could have the call in
> mainwindow and the depencies wouldn't change.  FWIW, I don't see why
> putting the call into classifier would be a problem.
> 
> Note: mainwindow is always the module Thuban.UI.mainwindow here, in case
> that wasn't clear from context which is sometimes hard to tell in
> conversations stretching over months :)
> 
> > Similar code is required for other layers, too (e.g. currently WMS
> > layers).  Should that code go into mainwindow as well?
> 
> For layers in extensions definitely not.

Great, now we're discussing in a circle and can restart where we were
on Jul 27th 2004 already, nearly one and a half month ago.

So... let's restart this issue again:

Problem:

    Different layer types require different properties dialogs.

Solution:

    Set up a hash of layer classes and properties dialog classes.
    Each layer class will register itself and the respective
    properties dialoc class upon Thuban startup.

    Advantage:

        The solution is independent of the number of different layers
        and can easily be enhanced in the future (i.e. just register
        more layer:dialog class pairs.

    Disadvantage

        This solution requires:

	a) a global variable (_properties_dialogs) for the ClassMapper

	b) a globally available register function/method

	c) the register function/method needs to access the global
	   variable and needs to be able to be imported into
	   potentially any .py file (currently only
	   Thuban/UI/classifier.py and Extensions/wms/wms.py).

        Solved: a)
	Not solved: b), c)

Proposal:

    Add Thuban/UI/propdialgs.py (or any other name) with (as stated in
    the July 27th mail):

    a) the declaration of the global variable

    b) the global register function

    c) the access function to make it complete [optional]

       Since in practice only mainwindow needs to look up the mapping,
       this isn't required and can be done directly in mainwindow as
       well, but it would break the modular concept a bit.

Would that be acceptable for you?

Regards,

	Joey

-- 
The good thing about standards is that there are so many to choose from.
		-- Andrew S. Tanenbaum