[QGIS-Developer] Run processing model on selected features only

[Matthias Kuhn]

Hi Nyall


On 12/13/17 11:20 PM, Nyall Dawson wrote:
> On 12 December 2017 at 00:10, Andreas Neumann <a.neumann at carto.net> wrote:
>> Thanks for the information. Unfortunately I cannot use "Feature Source" as
>> an input in my model.
>>
>> Matthias told me that I have to use "Vector layer" as an input, because my
>> model relies on certain features that aren't available on "feature source"
>> inputs. I need to use refactor fields in a model with expressions support
>> for relation_aggregates and represent_value (which requires information on
>> widget configuration).
>>
> Hi Andreas,
>
> Thanks for your feedback while testing the new processing modeler...
> it's very valuable information!
>
>> I also find it quite confusing that the inputs come with zero documentation.
>> I think for probably 99% of the users who are not devs it isn't obvious when
>> to use which input. Could we introduce a very simple tooltip that explains
>> with 1 or 2 sentences what the input implies - esp. for the "Vector layer"
>> vs. "Feature Source" vs. "Layer field" ?
> I need to improve how this is exposed in the modeler, but the
> difference between "Feature sources" and "vector layers" is that
> feature sources are used wherever *features* from a layer are being
> processed, vs "vector layer" parameters which are for processes which
> alter the whole layer (e.g changing its style, adding a field in
> place, deleting/renaming it, etc)
>
> Accordingly, all algorithms which edit features should be made to work
> fully with "feature sources". In this case, we need to fix the
> refactor fields algorithm to handle the relation/represent value use
> cases somehow. But the proper solution here isn't to require a vector
> layer parameter.

When relations are involved, there needs to be a vector layer around to
work with these as far as I can see.
If this vector layer is promoted from a feature source parameter or
provided as vector layer input is a different question (I can live with
both).

For a really nice UX, the expressions in the algorithms would be
analyzed for if they require only attributes/geometries or other layer
specific information and complain if they get an input that's
incompatible with their expectations. But that's quite a bit of work for
probably not so many use cases so I wouldn't put that on high priority.

>
> (Note that ALL algorithms which use feature source parameters will
> happily accept a vector layer parameter and operate on the all the
> features in that layer... but that's just done to make the modeler as
> flexible as possible).
>
> I plan on renaming "Feature Source" -> "Vector layer features" in the
> modeler to help clarify this (also "layer field" -> "vector layer
> field"), and I'll add some tooltips too. (also sort that list)

That sounds good to me, +1

Matthias

>
>> Is there any chance this checkbox could also be introduced for "Vector
>> layer" inputs? Should I open an issue?
> Based on the above - no. Vector Layer parameters operate on a whole
> layer... so what would a "selected features" checkbox mean for an
> algorithm like "rename layer"? Or for setting layer styles? It's just
> opening up a can of worms....
>
> Another (related) question. I've been thinking model input UI should
> be reworked. My proposal:
> - remove the list of input types
> - change it to a dock with a list of inputs present in the current
> model, with an "add" (and remove) button to add new inputs to the
> model (at which point the input type selection will be asked)
> - add up/down reordering controls for inputs (supported in the backed,
> but in the frontend there's no way to set the ordering. Which is a
> pain for making end-user usable models)
>
> Thoughts?
>
> Nyall
>
>
>> On 2017-12-11 15:01, Mathieu Pellerin wrote:
>>
>> The global use only selected features option is gone (yay) in favor of a
>> checkbox which can be activated on a per-use basis. I believe iterating
>> through selected features only requires a vector source input.
>>
>> On Dec 11, 2017 20:57, "Andreas Neumann" <a.neumann at carto.net> wrote:
>>> Hi,
>>>
>>> In QGIS master (version 3), with a Vector Layer input, I am failing to
>>> find the option to run a processing model only on the selected features.
>>>
>>> Can you please help me find the setting? I looked in the "Options" -->
>>> "Settings" --> "Processing" or watched out for a checkbox in the "Run model
>>> dialog" - but both did not show an option to restrict on selected features
>>> only.
>>>
>>> Thanks for a hint,
>>>
>>> Andreas
>>>
>>>
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>>
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