[Kst] kst2 datasource API comments

[Peter Kümmel]

Barth Netterfield wrote:
> On March 16, 2010 02:38:30 pm Peter Kümmel wrote:
>> I've cleaned up the ascii.cpp code: splitted into more files,
>> removed the duplicates of key and tag names, and hopefully made
>> it more readable.
> 
> We should talk about plans with that.  I will attempt to get to writing an 
> improved ascii source document - things have been a little slow kst-wise for 
> me lately.
> 
>> Maybe it is also possible to simplify datasource.h
> 
> Can you send out a quick plan after looking at it.  I was looking at it last 
> week as well.  It is a bit of a mess, but....
> 

Reading datasource.h I had following ideas for DataSource:

- most static functions are for handling the plugins. This
  code could be splitted out into a other, new class: DataSourcePluginManager

- as Nicolas suggested I would add metadata to each data and would introduce
  a simple struct, something like

    struct DataSource::Info{
       QMap<QString, double> scalar;
       QMap<QString, QString> strings;
    };

  and then
    Info sourceInfo();
    Info fieldInfo(const QString&);
    Info matrixInfo(const QString&);

- Are there files which store fields and matrices? If not,
  I would introduce two classes which inherit from DataSource,
  on for vector data and one for matrices. The info and data
  lists becomes:

    QStringList dataList(); // vectors or matrices
    Info dataInfo(const QString&);

- somehow we should split out the update stuff, and implement it
  such way that a concrete DataSource implementations does not
  need to know anything about the update mechanism.

- make all functions which must be implemented pure virtual

- most of the static functions of DataSourcePluginInterface should
  be part of the concrete data source implementations: understands(),
  supportsTime(), ... are essentialle functions of the datasource
  not of the plugin infrastructure.

- why do we use malloc? We have C++.

Peter