feat(linux): add headers to URL scheme request

[wusyong]

What kind of change does this PR introduce?

• Bugfix
• Feature
• Docs
• New Binding issue #___
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change?

• Yes, and the changes were approved in issue #___
• No

Checklist

• When resolving issues, they are referenced in the PR's title (e.g fix: remove a typo, closes #___, #___)
• A change file is added if any packages will require a version bump due to this PR per the instructions in the readme.
• I have added a convincing reason for adding this feature, if necessary

Other information

[wusyong]

There's a race condition could cause page freeze right now.
Run custom_protocol example and hit the button quickly to constantly changing pages. You will get stuck at some point.
Sometimes it will even be blank page on start.
It will also stuck even if I just call http_headers and do nothing.

[wusyong]

I finally found the cause. So it seems the binding from webkit2gtk-rs will take header's ownership:
https://github.com/tauri-apps/webkit2gtk-rs/blob/crate/src/auto/uri_scheme_request.rs#L113
And the type in header field is a unique_ptr!
https://searchfox.org/wubkat/source/Source/WebKit/UIProcess/API/glib/WebKitURISchemeRequest.cpp#73
This cause a race condition that can result into use after free...

[wusyong]

@lucasfernog These methods require webkit2gtk 2.36. I think I probably need to add a feature flag for it. How do you think tauri should do? Also a flag to use it?

[lucasfernog]

@wusyong can we detect the webkit2gtk version at runtime and not call the API if the version is below 2.36? I think that would be the safest approach.

[wusyong]

Yes we can. I'll try this approach then.

[chairmanwow]

wry/src/webview/webkitgtk/web_context.rs

Line 255 in 16a7086

let http_request = match http_request.body(Vec::new()) {

It looks like this doesn't support POST with bodies, say for example JSON in the POST request body. Is there a reason why the body is being set to the empty vector? Does WebKitURISchemeRequest have no way of getting the body?

I tried this in an app sending POST's with JSON and the custom scheme handler can't see those. I'm happy to dig into this and try to get to a pull request if there's interest from the tauri side.

[wusyong]

@chairmanwow WebKitURISchemeRequest doesn't expose it yet. That's why there's still issue #666 for it. If you are interested in this, I suppose you can open a PR in Webkit directly to add it.

[chairmanwow]

Yikes, understood. Thanks for the effort and for clarifying the why for me.