Do content-sniffing for HTML

[The-Compiler]

When opening a local HTML file without .html extension, qutebrowser downloads the file instead of opening it.

Instead we should detect it's HTML and open it accordingly.

Ressources:

• WhatWG MIME Sniffing Standard
• Arora's implementation
• Eric's implementation

[The-Compiler]

Fixing this would mean changing qutebrowser.browser.webpage.on_unsupported_content to sniff the reply in the else branch, and then use self.display_content accordingly.

[l29ah]

I'd argue that it would make sense to view every file specified on the command line, as it should be much easier to implement and user must be knowing what is he doing when he does this. In fact, he won't ever want to "download" a local file.

[l29ah]

// in fact i'm upset that mutt can't view html in qutebrowser because it doesn't append ".html" to the temporary file's name

[The-Compiler]

Fair enough - though it still would need to set some kind of mimetype for them, and I'm not sure if it's a good idea to set text/html for everything local even if it's something completely different.

As a workaround, I think you can write a wrapper script which renames the file and launches qutebrowser on it, and then launch that from mutt.

[spaceone]

I wouldn't do this. I would always look at the Content-Type response header because this is the correct way to do things.
There is also a unofficial HTTP header X-Content-Type-Options which might have the value nosniff to prevent browsers (IE / Chrome) for doing such thing. Plus the Content-Disposition header should be evaluated.

[The-Compiler]

I don't think local files have HTTP headers 😉

[The-Compiler]

Looks like qutebrowser does the right thing with QtWebEngine here, and I don't want to implement that for QtWebKit only.

[The-Compiler]

Another reason to not do this: Chromium disabled mime sniffing for local files (without .html extension) for security reasons: https://bugs.chromium.org/p/chromium/issues/detail?id=777737