Callers arriving after the window is published but before the creator
has drained the queue took the existing-window fast path and could run
ahead of older queued operations, so a newer SetURL could be overwritten
by an older one. withWindow now queues every caller while the creating
flag is set and clears the flag only once the queue is seen empty under
the lock.
A factory panic or a nil window left the creating flag set and the slot
dead; creation and drain now reset that state on early exit.
hideOtherWindows records the windows it hid only when no restore ran
in between, tracked by a generation counter, and re-shows them otherwise,
so a restore racing the hide cannot strand hidden windows.
The Wails systray runs the left-click handler synchronously inside the
tray window procedure, and creating a window on a running app pumps a
nested Win32 message loop while WebView2 initialises. ensureWindow held
the non-reentrant createMu across that creation, so the second button-up
of a double click re-entered ShowWindow from the pump and blocked the
main thread on its own lock. A goroutine holding createMu while the main
thread pumped, and the Open* dialogs holding mu across NewWithOptions,
Show, Hide and InvokeSync, exposed the same inversion.
WindowManager now serialises creation with a per-slot creating flag and
queues the callers' operations until the window exists, and no Wails call
runs while mu is held. The tray click and second-instance handlers call
ShowWindow off the message loop.
Zoltán Papp