A single 306 KB GUI-subsystem binary with no tray icon and no settings
window: one hidden popup owns the hotkey, the device-change callbacks and
the flyout, and the process sleeps in GetMessageW at 0% CPU in between.
Windows exposes no public API for setting the default audio endpoint, so
this uses the undocumented IPolicyConfig COM interface, confined to
src/policy.rs. Verified working on build 26200. Everything else -
enumeration, IMMNotificationClient, RegisterHotKey, the flyout - is
documented Win32.
The flyout uses the DWM acrylic backdrop and rounded corners the shell
uses for its own flyouts, with text drawn via DrawThemeTextEx and
DTT_COMPOSITED into a 32-bpp DIB, which is what keeps GDI from leaving
black fringes on a composited surface.
Console and Multimedia roles move by default; Communications stays put so
voice chat keeps its headset. Config is a hand-parsed INI reloaded on the
next keypress, keeping the dependency list to the windows crate alone.
Built by cross-compiling from a devcontainer with mingw-w64, so nothing is
installed on the Windows host and the exe imports only system DLLs.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
