Add support for viewing downloaded documents

[eloquence]

As a journalist I want to be able to view a file submitted by a source in a common format (e.g., PDF, JPG, DOC, AVI) so that I can inspect it for potential newsworthiness.

As shown in the messaging prototype, after a document has been downloaded, it should be possible to launch an appropriate viewer application to open a decrypted submission, ideally in a hardened disposable VM.

[redshiftzero]

Hey @ntoll this is the next highest priority ticket, which to replace the on click handler associated with the open button (that appears when a file is downloaded):

with a handler that will open the file. The desired behavior of the file handler is:

• On Qubes: subprocess out to qvm-open-in-vm '$dispvm:sd-svs-disp' filename (we'll have someone test your PR on Qubes to ensure that this part works as anticipated)

• On non-Qubes: ideally we'd subprocess out to either xdg-open filename (linux) or open filename (macOS), but as this is for developers only, getting open working is not super important and we can just log a line to indicate that user opened file <filename>, and that open is supported on Qubes only

The proxy attribute here determines if the client is being executed on Qubes or not (True for Qubes, False for non-Qubes).

[kushaldas]

On non-Qubes: ideally we'd subprocess out to either xdg-open filename (linux) or open filename (macOS), but as this is for developers only, getting open working is not super important and we can just log a line to indicate that user opened file , and that open is supported on Qubes only

👍 to this. Only logging a line in case of non-Qubes system sounds so better.

[ntoll]

On it. :-)

[ninavizz]

Still from prototype that demonstrates opening a doc in a Disposable VM. Note: activity messaging (top-left of screen) and dialog that appears to let the user know what's going on for the 3-5sec it will take to boot the Disposable VM. Implemented as-shown here, a Beta goal—leaving here for reference. https://projects.invisionapp.com/share/R8OODHKSWY3#/screens/326625556