fixed textheight affects scrolling?

[Klaus major-k]

Hi friends,

strange phenomenon, maybe I am missing something!?
LC 9.6 on macOS 10.14.6

I have two fields with all available fonts and each line is formatted directly 
in the appropriate font it reads.

I set the FixedLineHeight for ONE field to 28, doesn't matter actually.

Now I want to select a specific line in the fields with this script:
-------------------------------
on mouseUp pMouseButton
  set the wholematches to TRUE
  put lineoffset("Lucida Grande",fld "fonts") into tLine
  ## Which is 366 in my fields!

  put the effective textheight of fld "fonts" into tTH
  set the scroll of fld "fonts" to tLine*tTH + the height of fld "fonts"
  set the hilitedlines of fld "fonts" to tLine
end mouseUp
-------------------------------

Works fine for the field WITHOUT fixedlineheigt and selects the line -> Lucida Grande
However the same script used with the field WITH fixedlineheight, it selects -> Lucida Grande Bold
which is the line AFTER "Lucida Grande" and actually line 367!?

What am I overlooking?
Thanks for any hints!


Best

Klaus
--

Klaus Major
https://www.major-k.de
klaus at major-k.de