Architecture · Gru docs

Core model for the public engine. Full chapters are on GitHub; this page is the map.

Core model

Retained mode · widgets live in a Node tree across frames. Mutate them; do not rebuild the tree every paint.
Phases · each frame is strictly Update → Layout (if dirty) → Draw. Do not layout from draw.
Document · owns Root, logical size, chrome insets, focus, and QueueMain / DrainQueue.
Dirty flags · layout and redraw run when needed; clean frames blit the last supersampled frame.
Signals · typical UI state is Signal[T]; writes mark dependents dirty.
Chrome · undecorated window + engine TitleBar; content sits below ChromeTop.

Frame loop

DrainQueue
Update (title bar + Root)
Layout if Root dirty
Draw into SSAA if NeedsRedraw, else blit cache
Present + overlays
[WebView: sync hosts after Layout; present after EndDrawing]

Chapter map

#	Chapter	Contents
1	overview	Retained mode, frame loop, dirty flags, Document
2	window-chrome	Undecorated window, TitleBar, drag, double-click, DWM
3	layout	Chrome insets, flex, Viewport vs fill-height
4	rendering	SSAA, overlay render targets, idle / wake
5	webview	HWND vs GL (see also WebView guide)
6	input-focus	Pointer routing, overlays, WebView focus handoff

Index: docs/architecture/README.md.

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