[QGIS-Developer] Processing Raster Calculator in Processing Modeler

[matteo]

Hi devs,

I made a search around issues, old PR and emails, but I didn't find any
discussion about that, if the topic has already been discussed, please
address me to the source :)

Very very simple issue: the expression parameter of the Processing
Raster Calculator cannot be set to a Model Input Parameter, so the
expression within a model is always "hardcoded".

E.g. the GDAL Raster Caculator Formula Parameter is a String and can be
set to a Model Input Parameter.

The syntax of the native Processing Calculator cannot be easy to embed
in a string ("dtm at 1"......), but if I'm not wrong, the Processing Raster
Calculator can be used in "just" a simple way within a model even if it
is super powerful!

Cheers

Matteo