[Bf-taskforce25] operators and context

[Joshua Leung]

Hi,

It seems to me that the context should merely act as some container for that
provides some limits for getting access to relevant data (i.e. 3d-view would
only ever return objects or bones, buttons window would only return settings
on active object relating to ob-data or materials, etc.). An operator would
need to have expectations for what sorts of data it can operate on, and will
make requests to the context to get data that fits those criteria. The
operator would then work on the data it is given by the context, probably
needing to know what type of data it is and then delegating to some
sub-operator that only works on some particular type of data.

By doing things this way, the viewer/space/whatever creates the context,
doesn't need to know what it needs to supply to a specific operator. In some
senses, that is quite good, as the demands of different operators can differ
quite greatly. Also, by doing it this way, we can centralise the 'obtain
appropriate data to edit' issue, so that each operator doesn't end up
implementing it. There would need to be a set of methods to retrieve certain
types of data from the context. This is where I think there is a potential
level of overlap with Data-API type stuff. We could say that while Data-API
is more properties-based, context is more about the structs that those
properties come from.

Probably this is just coming from own biased opinions on the matter: reading
over this, it seems to quite closely resemble how current Action Editor
implementation works. Also the new keyframing code is a bit like this to
some degree (bCommonKeySrc being an example of what I envisage the operators
working on). Perhaps I have also just restated some of the other ideas
presented here in a slightly different way too.

Anyways, that's just my 2c (NZ) on the matter ;)
Joshua
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