WebView

When to use it

Use WebView when part of the UI is best done in HTML (docs pane, map, rich editor) and the rest should stay native Gru widgets and chrome. Start from cmd/webviewhello or gru new myapp --webview.

Build tags

go run -tags webview2 ./cmd/webviewhello
go run -tags "grudemo,webview2" .
go run ./cmd/gru build webviewhello -webview2

Requires the Microsoft Edge WebView2 Runtime.

Rules

• FillClient · the web view fills the client area below the title bar and resizes with the window.
• Two surfaces · GL draws the Gru tree; WebView is a separate HWND. Hide the HWND when a modal needs hits over that area.
• Focus · hand focus between native widgets and the web view explicitly (see Focus Handoff demo).

Modals and overlays (occlusion)

The live WebView2 HWND sits above the OpenGL blit. A native modal drawn in Raylib cannot paint on top of that HWND, so Gru hides live hosts while a blocking overlay is open.

• Use ui.ShowModal(...) (or drawer APIs); engine sets WebViewHostOccluded for you.
• Keep the modal body flat flex — no Viewport as modal root.
• Verify in WebView Focus Handoff with -tags webview2.
• Do not invent click-through / passthrough so GL “shows through” the web.

Debug

Set GRU_WEBVIEW_DEBUG=1 and use Shift+F11 for stderr traces. F12 is still the widget inspector.

Demos

• WebView Module Demo
• WebView Focus Handoff

Run with -tags "grudemo,webview2", then Tab to those scenes.

Full guide: WEBVIEW.md · chapter: architecture/webview.md.

Next: Architecture · Layout · Start