Disable "Print" when file format is not conducive to printing

[ninavizz]

Problem

A bit to file in the "duh" bucket, and thus something I'm not at all worried about until the post-Pilot release...

Ya can't print a video file. Or a song, or a ZIP, an EXE, etc. As such, the obviousness of this qualifies it as a low-priority to me, at the time of this filling.

Solution

Disable the "Print" text-link next to files that are somehow not printable; be they compressed archives, videos, audio, or any other non-printable dealie-o. On second thought, perhaps best to approach this as only enabling the "Print" button to be live, for supported/known filetypes that can deal with printing. Images less than 100mb (or whatever), .doc, .pdf, .xls, .txt, etc.

[ninavizz]

Spreadsheet here, nice guide for where to do.

[gonzalo-bulnes]

Cross-referencing https://github.com/freedomofpress/securedrop-workstation/issues/842 because it is a step towards fixing this issue.

[gonzalo-bulnes]

Removing the needs discussion label because the discussion is ongoing. Also this triggers widely unexpected behavior, so I'm labeling it as a bug.

[deeplow]

One thing to note about this is that "guessing" the file format requires some light parsing of the file. On Dangerzone we had a similar challenge. That's why we always deferred the "convertibility" check the unstrusted component. However, on Qubes, that requires starting a VM.

So I see a few approaches:

1. We investigate how the parsing is done and conclude if its parsing language is just regular expressions, then I guess it could be fine to do in sd-app.
2. If not, then we may be stuck with having to detect the profitability on the untrusted component.

[deeplow]

Or perhaps I am misunderstanding and the goal here is to disable the print on the print dialog itself rather than on the conversation view. If that's the case, please disregard my comment.