Offer to install WebView2, with an administrator prompt, on Windows

[beingsuz]

Requested by beingsuz · project thread

Stacked on #3: the base is #3's branch, so this diff shows only the WebView2 work. Once #3 merges, this retargets to main. It goes with UnhingedSoftware/kirie's "Show web wallpapers on Windows through WebView2".

Before: on Windows, web wallpapers could not run at all, and nothing in haru knew what they would need.

After: kirie shows web wallpapers on Windows in the Microsoft Edge WebView2 Runtime. When a machine does not have it, the install-kirie prompt offers "Also install WebView2, for web wallpapers", and Settings › Renderer shows whether it is installed, with an Install WebView2… button. Either one downloads Microsoft's installer, and Windows puts up its administrator (UAC) prompt before it runs.

The downloaded installer is run as administrator, so haru checks it first: it must carry a valid Authenticode signature from Microsoft Corporation, or it is not run.

How:

• Detection: haru_apply::webview2::installed() reads the runtime's pv value from the registry keys Microsoft's guidance names (per-machine, both registry views, and per-user). It treats an empty value or 0.0.0.0 as not installed.
• Install: install() downloads the Evergreen bootstrapper from Microsoft's fwlink. A PowerShell script then checks it with Get-AuthenticodeSignature and runs it with Start-Process -Verb RunAs -Wait and /silent /install. A declined prompt, a bad signature and a failed installer each come back as their own message.
• After a failed WebView2 install: a good kirie install is kept, and the prompt says web wallpapers will not run yet.

How it was tested

• cargo fmt --all, cargo clippy --workspace --all-targets -- -D warnings and cargo test --workspace are clean on Linux.
• The same clippy run is clean for x86_64-pc-windows-gnu.
• New tests cover reading the version from reg output (including the leftover-key cases) and that the script checks the signature before it elevates, including a path containing a quote.

Not tested: nothing here has run on Windows. In particular, the UAC prompt, the signature check and the bootstrapper's /silent /install have not been seen working.

🤖 Generated with Claude Code

https://claude.ai/code/session_01QJnt7JtdtiqnVCP9GYqUhK

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Generated by Claude Code

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