Ability to directly view further attachments from email

Feature Request

#5701 was marked as closed by #5898, but IISC that only adds previews for images and not other files (e.g. pdfs). the preview is also only renders a small thumb at the bottom of the mail and one can't view the picture in full-screen without downloading it to PC/NC. (Please correctly me, if I got anything wrong here!)

From #2225 I understand that it's not straight forward to display arbitrary files, also because interaction with other NC components is necessary. However, from the discussion in #5701 and #5898 it's not clear to me whether or not previewing other file types is completely dropped or not.
If it's too complicated to get on any road map, feel free to close. If there is a chance that this could be implemented at some point, I would ask to keep this open :)

• https://github.com/nextcloud/mail/issues/6983
• Office formats
• Text https://github.com/nextcloud/text/pull/2832
• Other Viewer types: https://github.com/search?p=1&q=%22OCA.Viewer.registerHandler%22&type=Code

Summary

Ideally, I would like a preview to use the default tool assigned for the file type (if there is one), e.g. the markdown editor for .md files, pdf viewer for pdfs, OnlyOffice for .docx & friends, …

TBH, right now I'd already be happy if I could print PDF-attachments without having to download them to my PC/NC first :D

Review issues #5701, #5898, and #2225, plus #6983, the Text pull request #2832, and the search for OCA.Viewer.registerHandler. Use those discussions to determine which attachment types and viewer integrations are supported. Done means the agreed attachment types can be opened or printed through the appropriate viewer without downloading them first.