[QGIS-Developer] Drill-down (cascading) forms in QGIS Value Relation Widgets crowdfunding

[Alessandro Pasotti]

Hi,

I'll try to address all concerns in a single mail (what a challenge!)

First I would like to say that everybody has access to a different set of
"average/typical users" and I cannot claim any statistical relevance to the
group of users I've been in touch with.

But the user's feedback that I've got so far is that the Value-Relation
widget (V-RW) is easier to use and to understand: its scope it's limited to
how data are entered and viewed and does not depend on a
model-project-level constraint (the Relation-Reference R-RW does).

Those (statistically insignificant) users were quite emotional and ready to
fight to keep V-RW live and healthy :)

Code-wise I totally agree that the two widgets could share more logic and
options, but given the intricacies of the attr-table and widgets-forms
logic this is not trivial at all, and it's not in scope with this QEP 116
enhancement.

Coming to the new functionalities introduced by QEP 116, the way they will
be implemented will make them easily reusable in the context of the R-RW:

- form scope context with geometry and attributes
- form scope available in both the form and the attribute table

Of course existing bugs and glitches in the V-RW workflow will be fixed on
the way when they not imply rewriting the whole QGIS core ;)


What could be considered here, is to add a second goal to the campaign for
making the new features available to the R-RW too, what do you think?

But even without this additional goal, I still think that this QEP (which
is not a complete refactoring of the whole form/attr-table *-R widgets) is
a step forward and in the direction of a future better integration of the
existing *-R-widgets.


That's why I'm joining Nyall's call to contribute and make this a reality.


Also note that some of Règis requirements, like a geographical dynamic
filter will be possible with an expression like:

... AND contains(buffer( $current_form_geometry, 10), $geometry)

note that this expression is the one used to filter the values in the
related layer, and it will have access to the geometry of the feature
currently being edited/added in the form (or table row) as well as to the
form (row) values, so:

- $current_form_geometry = the geometry of the feature currently being
edited in the form
- $geometry = the geometry of the related layer that is being filtered to
get the list of values for the combo/search/etc...

Also note that the V-RW is already used in the identify results panel (and
form of course).


Cheers

-- 
Alessandro Pasotti
w3:   www.itopen.it
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