File/media attachment improvements

[kevinaboos]

Now that we have support for attaching files & images, we should make some improvements:

• Support decryption and preview of encrypted media attachments: MediaSource::Encrypted, not just Plain
  • Implemented by Handle encrypted MediaSources properly, display encrypted media #882
• Show previews of text files, e.g., plaintext, code, etc
• When a preview cannot be generated, show a larger message that says something like "no preview available" instead of just a tiny file icon and the mimetype
• Now that we utilize rfd on desktop, we can also support downloading files/images within messages
  • Implemented by Support downloading media attachements, e.g., files, photos #880
• Experiment with showing inline PDF previews using Makepad's new PDF viewer support

[matlu]

Great for PDF attachments, can we use the Makepad PDF viewer or are we dependent on System OS features for this like the "Preview" on MacOS and iOS and Microsoft EDGE under Windows 11. I assume these means having to open external apps so user is forced to leave Robrix to view it. I think most users would like to keep viewing experience within Robrix and e.g., the PDF is opened and viewed by the Robrix client using the Makepad PDF viewer.

@kevinaboos

[kevinaboos]

well we can ultimately add previews of nearly any kind of file, at the cost of app size and complexity. PDFs, yes, though i'd note that no other clients offer PDF previews (to my knowledge). It'd probably be better to just offer a button to open it in the system viewer, which is also on my to-do list as part of the robius-file-picker crate

[kevinaboos]

i'll take a look at Makepad's PDF support, maybe that's an easy option!

[matlu]

Looks like Element X has support for viewing PDFs. Tried sending a file to you and looks like it opens it natively (maybe using its CEF which is it built with).
Indeed opening PDFs I think is important for a messaging app. As you can have boarding passes, hotel reservations, conference tickets, car reservations, etc. as PDFs that you would like to share and always be able to preview.

[kevinaboos]

viewing files is what I'm working on right now (as in, downloading them and opening them in the system-default app). Previewing is a different thing entirely (by that i mean playing it directly within Robrix without leaving the app), which i certainly want to do but requires many many more dependencies and complexity to get it right