Re: [guppi-list] Re: Plot idl

[Havoc Pennington <rhpennin midway uchicago edu>]

These are very helpful and concrete suggestions. Thanks for taking the
time to write...

On Wed, 16 Sep 1998, Dean Brettle wrote:  
 
> 1.  You make heavy use of attributes.  This saves you the trouble of
> having to write separate get/set IDL interfaces for each field.
> Unfortunately, attributes can't throw exceptions. 

I didn't think of that; will change it.

> 2.  Possible performance issues with get_value() and set_value().  If I
> want to get or set a large contiguous set of values, I will need to call
> these methods many times.  Doing this through CORBA can be very slow. 
> You might be better off with something like this: 
> 
>   Values get_values(in unsigned long start_index, in unsigned count)
>     raises (OutOfRange)
> 
>   void set_values(in unsigned long start_index, in Values value)
>     raises (OutOfRange)
>

Very nice.
 
> 3.  Different ValueTypes on the same Axis.  What should a Plot
> implementation do with an axis that contains both strings and doubles? 

I'm not actually sure what Gnumeric intends to do with the string value
type, and int can be subsumed by double. So it may be possible to get rid
of the union entirely. 

Assuming it remains, can I indicate in the IDL that a sequence has to
have homogeneous type, or is this just something to document?

> I recommend having each type of
> plot consist of the appropriate Axis descriptions (start/stop, auto,
> tick spacing, etc.) and separate homogeneous values arrays.  For
> example:
> 

Oops, you're right. Guppi can actually do multi-axis plots so I don't know
what I was thinking not exporting that functionality. One thing Guppi
can't do yet is overlay one plot on another; in that case you have a
single axis and multiple value arrays. (I guess you are referring to the
overlay case?) 

Anyway, to cover both of these cases, maybe have a sequence of Axis, where
an Axis has start/stop, categorical/scalar, etc., and each Axis can
control a sequence of Value to be plotted on that axis? That might work
well. 

This is actually a better way to organize Guppi's internals too. Right now
my axis class can only hold a single array of values. (My main worry is
how to organize the user interface - these dang plots are so complicated,
it's hard to put all the options on the screen.)

> Anyway, that my $.02 worth.  I hope its helpful.
>

Very much so. 
 
Thanks,
Havoc