Gradient background for Calc cells

[Ilmari Lauhakangas]

Andreas Heinisch is looking into 
https://bugs.documentfoundation.org/show_bug.cgi?id=49177

He has a WIP patch for it in https://gerrit.libreoffice.org/c/core/+/114103

He was seeking for advice in the dev chat and I thought to copy it to 
the list as well.

The question was:

Currently, I select the gradient in the gradient picker and now I am 
missing the overall picture. Do I have to create a new brush item in 
order to draw the gradient in
https://opengrok.libreoffice.org/xref/core/sc/source/ui/view/output.cxx?r=3092322b#1019

Ilmari