STR: 1. Turn on Preferences->Message View->Text Options->Smooth scroll and set it to any number of pixels 2. Half page can be on or off EXPECTED: Scrolling should be smooth and if half page is turned on it should result in half page scrolling. ACTUAL: Setting these preferences changes nothing. Scrolling is not smooth and is not in half-pages. [Tested in version 3.16.0git237]
Half-page scrolling does work, but only when pressing Space or Shift+Space. PageUp/PageDown still scroll the whole page regardless of the setting. I have a possible fix for that. As for smooth scrolling, I think this option should be removed. It seems it's been made nonfunctional by some GTK+ optimization somewhere in past few years, and I don't see a way to make it working again.
FWIW, the half-page scrolling has been fixed for a while, with commit https://git.claws-mail.org/?p=claws.git;a=commitdiff;h=5b0e5014b