Windows overlay SDK: HUDs, interactive panels, PiP thumbnails, tray icons. High-perf Rust core with bindings for TypeScript, C, Python, Go, Zig, and any language via JSON-RPC.

Examples are draggable, remember their position, and default to the bottom-right corner. Most support --no-titlebar, --position X,Y, --monitor N, and more — run any example with --help to see its flags.

cargo run -p winpane --example clock_overlay
cargo run -p winpane --example countdown_timer
cargo run -p winpane --example system_monitor -- --no-titlebar
cargo run -p winpane --example stock_ticker -- --monitor 1
cargo run -p winpane --example glucose_monitor -- --demo --unit mmol --no-titlebar
cargo run -p winpane --example capture_excluded -- --position 100,100

# see all flags for any example
cargo run -p winpane --example clock_overlay -- --help

pip_viewer and anchored_companion look for an open Notepad or Calculator window. All examples run without configuration — network-dependent ones fall back to simulated data.

• Transparent always-on-top windows via DirectComposition — no GDI, no process injection
• GPU-accelerated rendering: D3D11 → DXGI swap chain → D2D device context → DirectComposition visual
• Retained-mode scene graph — add rects, text, images; winpane handles the draw loop
• Multi-language: Rust API, Node.js addon (napi-rs), C ABI (cbindgen), JSON-RPC CLI for Python/Go/Zig/anything
• Built-in DPI awareness, capture exclusion, Mica/Acrylic backdrops, fade animations, system tray, drag, hit testing

Not a UI framework. No layout engine, no CSS, no widgets. You position elements with x/y coordinates.

Not cross-platform. Windows only, by design. Uses DirectComposition, which has no equivalent on other operating systems.

Not a game render-loop hook. DirectComposition composites outside the game process, adding 1–3 ms. Fine for MMO dashboards, strategy game tools, or any overlay where a couple of milliseconds don't matter. Competitive twitch shooters that need sub-frame precision typically inject into the render pipeline instead.

These compose together — a tray icon can toggle a panel, a panel can anchor to another window, any surface can fade and exclude itself from screenshots.

cargo add winpane

npm install winpane

Or build from source.

Link against winpane_ffi.dll and include winpane.h (generated by cbindgen). Build the DLL:

cargo build -p winpane-ffi --release

Spawn the winpane-host CLI binary, talk JSON-RPC 2.0 over stdin/stdout. Build:

cargo build -p winpane-host --release

import { WinPane } from "winpane";

const wp = new WinPane();
const hud = wp.createHud({ width: 300, height: 100, x: 100, y: 100 });

wp.setRect(hud, "bg", {
  x: 0, y: 0, width: 300, height: 100,
  fill: "#14141ec8", cornerRadius: 8,
});
wp.setText(hud, "msg", {
  text: "Hello from winpane",
  x: 16, y: 16, fontSize: 18,
});
wp.show(hud);

This creates a transparent, click-through overlay at (100, 100) with a rounded dark background and white text. The surface stays on top of all windows, invisible to screen capture if you want it to be.

If building from source, see the TypeScript guide.

• Rust
• Node.js
• TypeScript / JavaScript
• C / C++
• Go
• Zig
• Python / any language (JSON-RPC)
• Cookbook — 10 self-contained recipes

• Design overview — architecture, key decisions
• JSON-RPC protocol — full method reference for winpane-host
• Limitations — known constraints and workarounds
• Signing and distribution — code signing, SmartScreen, MSIX

• Windows 10 version 1903 or later
• Windows 11 22H2+ for backdrop effects (Mica, Acrylic)
• Windows 10 2004+ for capture exclusion

Pre-1.0. The API works and examples run, but expect breaking changes. Bug reports and feedback welcome.

I was diagnosed with Type 1 diabetes in 2025. Most CGM apps are geolocked and unavailable in Kenya, so I built mysukari.com — a free platform that connects any CGM via Nightscout for reporting (view my dashboard) and analysis. I wanted a small desktop overlay showing my glucose reading and trend arrow, updating every few minutes, hidden from screen shares. Nothing lightweight and multi-language existed, so I built winpane.

I had no prior experience with DirectComposition, Direct2D, or Win32 GPU rendering. GitHub Copilot with Claude Opus 4.6 was instrumental in building this.

MIT