Gru

What it is

Gru (GRU) is a retained-mode UI toolkit for desktop apps written in Go. The public package is github.com/ledocorp/gru/ui: widgets, layout, text, theme, window chrome, and an inspector. You import it like any other module, then either copy cmd/hello or scaffold with the gru CLI.

Primary platform today is Windows. Linux builds exist for basic samples. License is GPLv3. Governance is BDFL (no public PRs). Current release is 0.8.0 (first public cut was 0.7.0). Quick refs: cheatsheet · Gru Notepad.

How it works

• Retained tree · widgets are Nodes that persist across frames (not rebuilt every paint)
• Frame phases · each frame is Update → Layout (if dirty) → Draw / blit
• Document · owns the root, chrome insets (title bar), focus, and the main-thread work queue
• Signals · UI state is usually Signal[T]; mutations mark the tree dirty
• Composition · build pages with flex + Panel / Card / ListTile (named shell recipes in the docs)
• Rendering · Raylib + supersampled draw when needed; idle frames blit the last frame
• WebView2 · optional child HWND host for HTML; native widgets stay in the GL tree

What you use it for

• Desktop tools and utilities with native-feeling chrome and controls
• Apps that need a Go widget tree plus an occasional embedded web view
• Learning patterns from the curated demo catalog (-tags grudemo)

Gru Notepad

Gru Notepad is a product-shaped showcase of the toolkit: edge shell, editor, multi-doc sessions, markdown preview, syntax highlight, and spell check in one thin host. It lives in a separate repository and depends on this module (require github.com/ledocorp/gru).

Showcase page with clips · shawnlondono/gru-notepad

Try it

Grab a Go toolchain and open a window in a minute. WebView samples also need the WebView2 Runtime (Windows). Start from the getting started guide or v0.8.0.

go get github.com/ledocorp/gru@v0.8.0

# from a clone of github.com/ledocorp/GRU:
go run ./cmd/hello
go run -tags webview2 ./cmd/webviewhello
go run -tags grudemo .          # scenes; Tab / F12
go run ./cmd/gru new myapp

GPLv3 · LedoCorp · version 0.8.0

What’s in the package

• ui/ · widgets, layout, text, inspector, theme
• cmd/gru · new, build, package
• cmd/hello · minimal native sample (copy this loop)
• cmd/webviewhello · FillClient WebView sample
• -tags grudemo · scene catalog for composition and controls
• docs/ · guides + architecture chapters (also summarized on this site)