winpane

winpane

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.

Demo

Try it

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.

All examples

Rust

Example	What it does
clock_overlay	Live desktop clock, updates every second
glucose_monitor	CGM overlay — polls Nightscout or uses simulated data
stock_ticker	Stock prices with live/simulated data
countdown_timer	Interactive timer with Start/Reset buttons
system_monitor	Real CPU and memory usage
color_picker	Pixel color under cursor, updated live
sticky_notes	Floating notes, toggled via tray icon
interactive_panel	Clickable buttons, hover effects, drag
tray_ticker	System tray icon with popup panel
pip_viewer	Live thumbnail of another window
anchored_companion	Panel that follows another window
hud_demo	Basic stats overlay
backdrop_demo	Mica / Acrylic backdrop effects (Win11)
fade_demo	Fade-in / fade-out animations
capture_excluded	Overlay hidden from screen capture
custom_draw	Procedural D2D drawing

Run any Rust example: cargo run -p winpane --example <name>. Some examples may be buggy, please report issues, contributions welcome!

TypeScript

examples/typescript/: clock_overlay.ts, glucose_monitor.ts, pomodoro.ts, sticky_notes.ts, stock_ticker.ts

Run: npx tsx examples/typescript/<name>.ts (requires addon built; see TypeScript guide)

Python (JSON-RPC)

examples/python/: clock_overlay.py, glucose_monitor.py, hud_demo.py

Run: python examples/python/<name>.py (requires winpane-host built; see Python guide)

Node.js

examples/node/: backdrop_demo.js, hud_demo.js, interactive_panel.js

Run: node examples/node/<name>.js (requires addon built; see Node.js guide)

C

examples/c/: custom_draw.c, hello_hud.c

See build.bat or CMakeLists.txt for build instructions.

What it does

• 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

What it does NOT

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.

Surface types

Type	Behavior	Use case
Hud	Click-through, topmost, no taskbar entry	Stats overlays, notifications, timers
Panel	Interactive — hit testing, click/hover events, drag	Tool palettes, floating controls, popups
Pip	Live DWM thumbnail of another window	Preview panels, reference windows
Tray	System tray icon with popup panel and context menu	Background app controls, status indicators

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.

Install

Rust

cargo add winpane

Node.js / Bun

npm install winpane

Or build from source.

C / C++

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

cargo build -p winpane-ffi --release

Any language

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

cargo build -p winpane-host --release

Quick start

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.

Guides

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

Reference

• 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

Platform

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

Status

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

Why I built this

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.

License

MIT