Rhino Input Overlay

A small always-on-top, click-through overlay that shows, near the cursor, which mouse button and which modifier keys (Ctrl/Cmd/Alt/Shift) are currently pressed. Intended for documentation / tutorial / screencast use.

The overlay is only visible while Rhino is the frontmost application, and it works over the whole Rhino UI — viewports, toolbars, panels, and dialogs — because it is a separate top-level window rather than a viewport display conduit.

Native Windows and macOS implementations are both available. They share the same visual design: a translucent white modifier badge next to a capsule mouse glyph whose pressed half is highlighted. Windows shows modifiers as Ctrl/Alt/Shift; macOS uses the native ⌃ ⌥ ⇧ ⌘ symbols (and includes Cmd). Both expose a Settings window for colours, sizes and placement.

Windows (windows/)

.NET 8 WinForms app. A layered, click-through, top-most window updated via UpdateLayeredWindow (per-pixel alpha → crisp glyph, no transparency-key halo). Global input is read with GetAsyncKeyState / GetCursorPos; the active app is checked with GetForegroundWindow (process name Rhino). DPI-aware (PerMonitorV2). No special permissions.

dotnet run --project windows
# or build:
dotnet build windows -c Release
# → windows/bin/Release/net8.0-windows/RhinoInputOverlay.exe

A tray icon appears; right-click → Exit to quit.

macOS (mac/)

Native Swift + AppKit app (single file, mac/main.swift). A borderless, click-through, top-most NSWindow drawn with Core Graphics. Global input is read from snapshot APIs (NSEvent.pressedMouseButtons / NSEvent.modifierFlags) plus a global .scrollWheel monitor for the wheel; the active app is checked via NSWorkspace.frontmostApplication (process name Rhino). No Accessibility permission required. Runs as an accessory (no Dock icon) with a menu bar item for Settings / Start / Stop / Quit. Point-based and Retina-correct (no DPI scaling needed).

cd mac
swiftc -O -o RhinoInputOverlay main.swift -framework Cocoa
./RhinoInputOverlay

Or build a proper .app bundle — so it launches without a Terminal window, carries the icon, and can be zipped for distribution:

cd mac
./make-app.sh && open RhinoInputOverlay.app   # universal (arm64 + x86_64) .app + .icns
./package.sh                                   # → RhinoInputOverlay.zip

The .app/.zip are universal but only ad-hoc signed (not notarized): on first launch from a download, right-click → Open (or System Settings → Privacy & Security → Open Anyway).

Tuning

Both apps have a Settings window (the five colours, mouse/text size, and signed X/Y distance from the cursor) that applies live. Settings persist per-user: %AppData%\RhinoInputOverlay\settings.json on Windows, ~/Library/Application Support/RhinoInputOverlay/settings.json on macOS.