[QGIS-Developer] Expression Functions: Where are they used in QGIS Desktop? Which ones won't work "outside"?

[DelazJ]

Hi,
I may have overlooked your list but note that anytime you find a
data-defined override button, there's an expression dialog behind (using
the Edit option), and this button is spread over layer properties dialog
(style, diagram, label...) and composer items' options (almost all).
Processing algorithms also have the expression engine.

Some update of the official docs (though we didn't go through each dialog)
https://docs.qgis.org/2.18/en/docs/user_manual/working_with_vector/expression.html

Harrissou

2017-05-07 17:01 GMT+02:00 Stefan Keller <sfkeller at gmail.com>:

> Hi,
>
> Tomorrow I'll be giving a Workshop about "Easy Programming QGIS with
> Python for custom Expression Functions (EFns)" [1].
>
> Question 1: Below you'll find an initial list I compiled where EFns
> are used in QGIS Desktop. => Did I miss an occurrence?
>
> Question 2: I tried to make a categorization for several reasons. One
> reason for this is to realize that a EFn may not work outside QGIS
> Desktop. Style-related EFns for example won't work currently in
> qgis2web or QGISCloud. => Any comments?
>
> :Stefan
>
> [1] https://2017.geopython.net/#schedule
>
> List where EFns are used in QGIS (probably incomplete):
>
> "Server-side" / data-related:
> * "Select features using an expression" (Layer property).
> * "Filtering features" while loading from source. Switch to the form
> view in the attribute table (button on bottom right corner) > click on
> 'Show All Features' (bottom left) and select 'Advanced Filter
> (Expression)'.
> * "Layer > Properties > Tab Fields" in Button "Text Edit" in Default-
> and in Constraints-Field.
> * "Layer > Properties > Tab Style" in "Label with".
> * "Field Calculator" to defining new or virtual fields (Layer property).
> * "Conditional formatting" in the attribute table (Create a new rule
> and set the condition to the output of a custom EFn).
> Analysis-related:
> * "Statistical Summary" Panel (Layer property).
> * "Atlas Generation" in the Print Composer. Project > Print Composer >
> Check 'generate an atlas' > Set CEF based values for page name, filter
> and output filename.
> "Client-side" / style-related:
> * "Map Tip" tool (Layer property).
> * "Rule based labeling". Layer Properties > Labels > Select Rule based
> labeling from the drop-down menu > Click on the '+' button and add a
> CEF based filter (... button).
> * Part of "Geometry generator" in "Style > Symbol Layer Type"
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