[Qgis-developer] Decoupling core/data and GUI part of widgets in 3.0

[Nyall Dawson]

On 31 August 2016 at 21:20, Matthias Kuhn <matthias at opengis.ch> wrote:
> Hi,
>
> On 08/31/2016 12:41 PM, Nyall Dawson wrote:
>> On 31 August 2016 at 16:56, Matthias Kuhn <matthias at opengis.ch> wrote:
>>> Hi,
>>>
>>> I've already got some ideas because it affects QField (where I'm about
>>> to drop the whole gui lib) as well.
>>>
>>> Implementing this in QGIS instead of QField is much preferred.
>>>
>>> From a technical perspective, I would propose to use a tree-like
>>> structure based on QVariants.
>>> They've got all it takes for this:
>>>
>>> QVariantMap can handle tree structures of key value pairs (for XML child
>>> nodes), a key "__attributes__" can be added to save the XML element
>>> attributes into.
>>>
>>> This way, the information can be read without knowledge about a
>>> particular widget's implementation details and is available directly
>>> from core. The widgets (or whatever part) can add the semantics on top
>>> in their own library.
>>
>> Just to clarify - are you proposing that only a map of widget
>> configuration is moved to core? I'd say the representValue function
>> for each widget should also should be moved across, otherwise we'll
>> end up with multiple code paths reimplementing the logic from each
>> widget + plugins having to redo this themselves.
>
> Good point,
>
> that will also be nice to have in core.
>
> In this case we'll end up with two registries and two factories
> (although only a few widgets will need core functionality).
> Or did you have a different idea in mind?

This is what I was thinking - I can't think of a nice way around this.

Nyall


>
> Matthias