Impress linespacing change

Hello,

I want to raise a discussion about the percent linespacing in impress.
The calculation has change starting from v5.4 and this commit : 
https://cgit.freedesktop.org/libreoffice/core/commit/?id=a7e6e4b220089a2d8a58ff10393d598a8b796fa5
(see also https://bugs.documentfoundation.org/show_bug.cgi?id=114628 and 
https://bugs.documentfoundation.org/show_bug.cgi?id=120525)

I don't think this patch is the good solution for the following reasons :

1- The new font ascent is arbitrary set to 80% of the new height, 
independently of the ascent/descent ratio of the font
2- changing maxascent and height values for the first line of a 
paragraph means that linespacing change will modify the space between 
the modified paragraph and the previous one.
3- there's a problem if you you use a font with "big" descent value (see 
bug 120525)
4- it mess up all my documents created with before v5.4 ;)

Here's my proposal :

- if we care about 2, we should revert the commit and go back with the 
previous calculation (but we'll still have the problem mentioned in bug 
114628, except if there's a solution to differentiate between first line 
of paragraph and first line of a textarea)
- else, we should decide if we want to keep 1 or respect the 
ascent-descent ratio
- in that case point 3 shouldn't be to difficult to solve

I'd like to have your opinion about this before going further.

Thanks in advance

A. RENAUDIN

(this is my first post here, so please apologize if this message is 
inappropriate or if there's better ways to expose the problem)