[QGIS-Developer] QEP 113: Allow injection of "label blocking regions" into QgsMapSettings

[Nyall Dawson]

Hi all,

Please see https://github.com/qgis/QGIS-Enhancement-Proposals/issues/113
for a new proposal covering proposed changes to the labeling and
QgsMapSettings API to allow for specification for "label blocking"
regions in a map render.

Label blocking regions will be useful for discouraging labels from
falling within "hidden" areas of a map. E.g. when a map annotation or
scalebar is displayed over a portion of the map, QGIS should attempt
to avoid placing labels in the obscured area below these annotations.
Similarly, within a print layout, if a map item has additional items
placed over it (such as a legend or north arrow), it is desirable that
labels should not be placed in map areas below these obscuring items.

(This proposal covers adding the API calls for supporting manual label
blocking regions only -- it is left to a future work to implement
automatic creation of these blocking regions for map-obscuring
elements.)

Comments and suggestions welcome!

Nyall