A native window

go-widgets/window opens a real window and runs a widget tree in it: layout, draw, present, translate input into toolkit.Event, repeat until the window closes.

w, err := window.Open(window.Config{Title: "Demo"})
if err != nil {
	return err
}
defer w.Close()
return w.Run(root) // root is any toolkit.Widget

Config also takes the initial size in logical points (zero asks for a readable default), the WM_CLASS instance and class, a Theme, and a RenderScale.

How Open chooses

Every back-end is CGO_ENABLED=0. The X11 one is the core protocol written from scratch over the socket — no Xlib, no XCB — with both byte orders, the Xauthority cookie, keysym mapping, PutImage tiled under the server’s request size, and the MIT-SHM fast path, the shared segment passed over SCM_RIGHTS. Windows is reached through the process’s own DLLs with syscall.NewLazyDLL and a syscall.NewCallback window procedure; macOS through the Objective-C runtime with purego.

The platform-independent part of each back-end — event mapping, coordinate maths, pixel packing, damage rectangles — lives in a codec covered at 100%, on every operating system. The thin platform glue is proven live: see Status.

Only what changed

A root that implements DamageRenderer (as toolkit/scene.HostRoot does) reports the rectangles it repainted, and every back-end but GTK4 presents only those: X11 through MIT-SHM ShmPutImage, Wayland through wl_shm damage, Cocoa, Win32, Android, wasmbox and the browser tab. The first frame, a resize and an X11 Expose still present the whole surface.

HiDPI

The default is one framebuffer pixel per logical point: the UI is laid out and painted at a readable size, and the compositor up-samples it. On Windows the window declares per-monitor DPI awareness and the OS scales the logical frame to the physical client area. RenderScale asks for a framebuffer at the panel’s real resolution, which is correct only for a root that lays out in device pixels.

Screens, and showing and hiding

window.Screens() lists the attached displays, primary first, in logical points with the desktop’s panels excluded, and may be called before Open. A screen’s name is the panel’s own ("DELL U2720Q", from its EDID), falling back to the connector ("HDMI-1") when it publishes none — and also when two attached panels publish the same one, since a name that cannot tell them apart is not a name.

window.Show, Hide and Raise take an open window off the screen without closing it and bring it back — what a tray application needs.

Focus is the platform’s to grant: under focus-stealing prevention, Raise may only mark the window as wanting attention, and cannot tell.