A window creates a GoOS Window with a client Canvas:

window Demo {
  title "Demo"
  x 40; y 40; width 400; height 240
  closable true
  titlebar true
  background "#EDEDED"

  onLoad { message "Ready."; }
}

• title (string) — caption. Defaults to the window's name.
• x, y (int) — screen position. Defaults 40, 40.
• width, height (int) — client size. Defaults 320, 240.
• closable (bool) — default true.
• titlebar (bool) — default true.
• background (colour) — optional fill; if omitted, system default.

Controls are built in declaration order. For overlapping visuals (e.g., an image placeholder then a label), declare the background first.

• Window Contents origin is top-left (0,0).
• All control coordinates are relative to the window client area.
• Controls inside a panel are relative to the panel's (x,y).

Labels can be centred horizontally across the window by setting centre true (or center, etc.). This uses the font metrics to compute x at build time.

label header {
  y 8; text "Giff Title"; textColour black; centre true
}

image nodes paint a grey framed placeholder rectangle (useful for layout). To paint solid areas, prefer a panel with a background.

panel banner {
  x 0; y 0; width 400; height 36; background "#C0D0FF"

  label title { x 8; y 10; text "Banner"; textColour black }
}