LibreOffice Impress PDF export anitations

Hello everyone,

I have just received a quite interesting question from one of our
user.[1] He wanted to know what are the transitions supported when
exporting slides as PDF from LibreOffice Impress. From now, the
documentation only mentions this statement:

Use transition effects
Select to export Impress slide transition effects to respective PDF effects.

This is a bit lacking details here. I checked the code and PDF spec but
I haven't been able to find the exact transitions supported.

Note in practice, to export more transitions, it is often recommended to
use ExpandAnimations extensions[2].

Thanks in advance for your enlightenment, for the fix you can bring to
the documentation and for your hard work.

Regards,

[1] https://twitter.com/zigazou/status/1143116695923580929

[2] https://github.com/monperrus/ExpandAnimations