On minimal window managers (fluxbox et al, the in-process XEmbed-tray
path) the WM neither centers small windows nor restores their position
across a hide -> show round-trip, so the main, Settings, and dialog
windows opened in the top-left corner instead of centered.
These windows are created Hidden, so Wails' Linux/GTK4 backend skips its
post-Show centering pass (gated on !Hidden) and InitialPosition has no
effect on an unrealized window. Re-center from Go after Show, gated on
the minimal-WM environment via a recenterOnShow predicate (set to
xembedTrayAvailable on Linux, nil on macOS/Windows where the WM handles
placement). centerWhenReady polls from a background goroutine until the
move actually lands -- Center() moves via raw X11, which no-ops while the
GdkSurface is still nil and GTK4 realizes it asynchronously after Show().
Also reorder xembed_host_linux.go so the static helpers (xembedTrayAvailable,
goMenuItemClicked) sit at the end, after the constructor and methods.
Zoltán Papp