[QGIS-Developer] QEP 133: An interface and registry for custom validity checks

[Nyall Dawson]

Hi all,

Just a quick notification of a recently filed QEP, "An interface and
registry for custom validity checks".

This proposal concerns an interface for custom "validity checks",
along with a corresponding registry of custom checks and GUI widgets
for summarising check results. (THIS PROPOSAL IS NOT RELATED TO
GEOMETRY VALIDITY!)

Initially the proposal is focused toward print layout validity checks,
but the interface has been designed to be generic enough to allow
alternative types of validity checks (e.g. project save validity
checks, processing model validity checks, etc. More details later).

The API is designed to be used both by internal validity checks and
also to be extended by custom, organisation-specific validity checks.
E.g., for print layout validity checks we could have:

In built checks:

- Warn on layout scalebars not connected to layout map items
- Warn on layout map items using known misleading CRSes -- e.g. web mercator.
- Warn on layout map items which include layers with broken data
sources (following earlier 3.6 work on allowing layers with broken
data sources to remain in projects)

Possible organisation specific checks, implemented via Python

- Check for missing items required by internal organisation policy,
e.g. layouts with no scalebar, north arrow.
- Check for layout maps which include layers deemed "bad" by
organisation policy -- e.g. block exports when a layout map item
includes a Google TMS layer.
- Check whether a label item exists with a "copyright ####" string
- Layer attribution checkers
- Spell checker

Please read full details at
https://github.com/qgis/QGIS-Enhancement-Proposals/issues/133.
Comments, suggestions and feedback are welcomed!

Nyall