Tauri 2.11 doesn't expose set_opacity on its WebviewWindow (open issue
tauri-apps/tauri#3279). Drop down to the Win32 API directly: ensure
WS_EX_LAYERED is set on the overlay HWND, then SetLayeredWindowAttributes
with an 0..255 alpha. This is true OS-level window translucency — the
same call Tauri will eventually wrap upstream — not a CSS shim.
windows crate version is pinned to 0.61 to match Tauri 2.11.x's
transitive dependency, so WebviewWindow::hwnd() returns a compatible
HWND with no diamond-dependency conflict.
Replaces the earlier eval-based opacity workaround in apply_state and
set_window_opacity. Both call sites now go through apply_window_opacity.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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