fix recenter?

client/ui/recenter_linux.go

@@ -2,16 +2,57 @@
 
 package main
 
+import (
+	"os"
+	"strings"
+)
+
 // recenterOnShowPredicate returns the predicate WindowManager uses to decide
 // whether to re-center its Go-shown windows (main, Settings) on each show.
 //
-// On Linux this is xembedTrayAvailable: re-centering is needed only in the
-// minimal-WM / in-process-XEmbed-tray environment, where the window manager
-// neither centers small windows for us nor restores their position across a
-// hide -> show round-trip. The predicate is evaluated per show (not once at
-// startup) because the XEmbed tray can appear after the UI starts — the panel
-// and the autostarted app race at login — and xembedTrayAvailable is a cheap,
-// side-effect-free selection-owner probe, fine to call repeatedly.
+// Re-centering is needed only on bare WMs (fluxbox, IceWM, twm …) that neither
+// place small windows for us nor restore their position across a hide -> show
+// round-trip — the same environment the in-process XEmbed tray host serves.
+// xembedTrayAvailable (a _NET_SYSTEM_TRAY_S0 selection-owner probe) detects
+// that host, but it is NOT a clean proxy for "bare WM": full desktops like
+// Cinnamon, MATE, XFCE and LXDE ship a legacy XEmbed systray AND a real
+// compositing WM (Muffin/Marco/xfwm4) that places windows itself. On those,
+// running the post-show X11 re-center makes the window visibly jump from the
+// WM's placement to ours (reported on Cinnamon/Mint/X11). So we additionally
+// require that the session does NOT advertise a known full desktop.
+//
+// Evaluated per show (not once at startup) because the XEmbed tray can appear
+// after the UI starts — the panel and the autostarted app race at login — and
+// xembedTrayAvailable is a cheap, side-effect-free selection-owner probe.
 func recenterOnShowPredicate() func() bool {
-	return xembedTrayAvailable
+	return func() bool {
+		return xembedTrayAvailable() && !inFullDesktopEnvironment()
+	}
+}
+
+// fullDesktopTokens are desktop-environment identifiers whose window manager
+// places and restores windows for us. Several also expose a legacy XEmbed
+// systray, so they must be excluded from the re-center path explicitly.
+// Matched case-insensitively against the colon-separated XDG_CURRENT_DESKTOP /
+// DESKTOP_SESSION tokens. Bare WMs leave these unset (or report their own name,
+// e.g. "Fluxbox"), which is absent here — so they still re-center.
+var fullDesktopTokens = []string{
+	"cinnamon", "mate", "xfce", "gnome", "kde", "plasma",
+	"lxde", "lxqt", "unity", "budgie", "deepin", "pantheon",
+}
+
+// inFullDesktopEnvironment reports whether the session advertises one of the
+// known full desktop environments via XDG_CURRENT_DESKTOP or DESKTOP_SESSION.
+func inFullDesktopEnvironment() bool {
+	for _, env := range []string{"XDG_CURRENT_DESKTOP", "DESKTOP_SESSION"} {
+		for _, tok := range strings.Split(os.Getenv(env), ":") {
+			tok = strings.ToLower(strings.TrimSpace(tok))
+			for _, full := range fullDesktopTokens {
+				if strings.Contains(tok, full) {
+					return true
+				}
+			}
+		}
+	}
+	return false
 }

client/ui/services/windowmanager.go

@@ -163,10 +163,12 @@ type WindowManager struct {
 	hiddenForLogin []application.Window
 	mu             sync.Mutex
 	// recenterOnShow reports whether Go should re-center the Go-shown
-	// windows (main, Settings) on each show. Only true in the minimal-WM /
-	// in-process XEmbed-tray environment, where the WM neither centers small
-	// windows for us nor restores their position across a hide -> show
-	// round-trip. On full desktops (GNOME/KDE) the WM handles placement, so
+	// windows (main, Settings) on each show. Only true on bare WMs (the
+	// in-process XEmbed-tray environment minus the full desktops — Cinnamon,
+	// MATE, XFCE … — that also expose an XEmbed systray), where the WM neither
+	// centers small windows for us nor restores their position across a
+	// hide -> show round-trip. On full desktops (GNOME/KDE/Cinnamon) the WM
+	// handles placement, so
 	// re-centering is unnecessary and would fight a window the user moved —
 	// there this stays nil and centerWhenReady is a no-op. Set by the Linux
 	// startup path via SetRecenterOnShow; nil on macOS/Windows and in tests.
@@ -649,9 +651,10 @@ func (s *WindowManager) ShowMain() {
 
 // SetRecenterOnShow installs the predicate that gates Go-side re-centering of
 // the main and Settings windows (see the recenterOnShow field). The Linux
-// startup path passes xembedTrayAvailable so re-centering happens only in the
-// minimal-WM / in-process-XEmbed-tray environment; macOS/Windows and tests
-// leave it unset, making centerWhenReady a no-op.
+// startup path passes a predicate that is true only on bare WMs (XEmbed tray
+// present and no full desktop advertised), so re-centering happens only where
+// the WM won't place windows for us; macOS/Windows and tests leave it unset,
+// making centerWhenReady a no-op.
 func (s *WindowManager) SetRecenterOnShow(pred func() bool) {
 	s.recenterOnShow = pred
 }