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

[Matthias Kuhn]

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?

Matthias