Allows raster nodata pixels to be colored in a specific (non-transparent) color.
Designed to match the "Display background value" option from ArcMap.
Sponsored by SLYR
Fixes#26087
Adds a new visitor pattern API for creation of visitors which visit
all the style entities (symbols, color ramps, text formats, and
label styles) associated with different objects. Can be used on a
renderer, map layer, or project wide level.
E.g. on a project wide level, allows collection of ALL the style
symbols/color ramps/text settings inside a project, including those
in layouts or annotations!
