Pluggable replacement for the built-in cursor-quadrant drop resolution.
Supplied via DroptargetOptions.positionResolver, it maps a pointer
location within a target to a drop Position (or null for no drop)
instead of the default threshold-band quadrant. Both DnD backends consult the
same resolver. When unset, the default quadrant behaviour applies unchanged.
Pluggable replacement for the built-in cursor-quadrant drop resolution. Supplied via DroptargetOptions.positionResolver, it maps a pointer location within a target to a drop Position (or
nullfor no drop) instead of the default threshold-band quadrant. Both DnD backends consult the same resolver. When unset, the default quadrant behaviour applies unchanged.