fdo75264 incorrect function name tips, suggestions wanted

Hi Kohei, all,

While typing a function name in a Calc cell (e.g. "=GC"), a tip (sometimes) appears above the cell 
with the first fitting function name.
However, when the function name contains a '_' or a '.' (e.g. GCD_ADD or PERCENTRANK.EXC), 
the tip doesn't show (cell content "=GCD_") or shows the wrong function name (cell content "=GCD_A" 
produces tip AVERAGE()).
This is because in sc/source/input/app/inputhdl.cxx, function ScInputHandler::UseFormulaData() the 
call in line
  OUString aText = pEngine->GetWord( 0, asel.nEndpos-1 );
breaks the function name as '_' and '.' are seen as word separators.

Also, there are 2 tips: one above the cell (showing just function name, with the behaviour as 
above) and one below the cell (showing function name plus arguments, for which I submitted a patch 
(https://gerrit.libreoffice.org/#/c/8143/).
The list (ScFormulaHandler::pFormulaData) used for the tip above seems to contain only function 
names for which 'extended' names also exists, e.g. GCD and GCD_ADD, GCD is in the list), whereas 
the list used for the tip below (ScFormulaHandler::pFormulaDataPara) seems to contain all functions.
When the function name has no 'extended' versions (e.g. AND), no tip shows.

Why is this?
I don't want to break things when trying to fix bug fdo75264 and I am a bit confused about the 
current ScInputHandler::UseFormulaData() code.


Winfried