Default tray icon behavior is lackluster

[brodmo]

Current implementation of handle_tray_icon_event in app.rs is this

    #[cfg(any(target_os = "windows", target_os = "linux", target_os = "macos"))]
    pub fn handle_tray_icon_event(&mut self, event: tray_icon::TrayIconEvent) {
        if let tray_icon::TrayIconEvent::Click {
            id: _,
            position: _,
            rect: _,
            button,
            button_state: _,
        } = event
        {
            if button == tray_icon::MouseButton::Left && self.tray_icon_show_window_on_click {
                for webview in self.webviews.values() {
                    webview.desktop_context.window.set_visible(true);
                    webview.desktop_context.window.set_focus();
                }
            }
        }
    }

I'm in the process of building a macOS menu bar app and I haven't found this default implementation helpful, quite the opposite. Now thankfully, #5361 adds a flag to disable it, so that solves the issue for me. Still, I think this default implementation should be improved. Here are my issues with it.

It fires twice

Since button_state is a wildcard, the logic runs twice, on button down and button up. It should be just button down.

It shows, but doesn't hide

This might be constrained to macOS, but I think that clicking the icon again to hide the window is expected behavior. Since visibility detection is tricky adding window hiding without disabling the default implementation requires an ungodly workaround. I think it should hide or show depending on visibility instead of always hide.

It focuses multiple windows in a non-deterministic order

This is my biggest gripe. The webview iteration order is non-deterministic, so it's random which window ends up with the final focus. Especially for a keyboard-driven app this is lethal. For me, it would randomly focus my invisible pop-up, which was really hard to debug. I don't have a good solution to this, though. Maybe the default implementation should just do nothing if there are multiple webviews? I'm not sure.

I'm willing to implement a solution to this, but since it mainly boils down to design questions I would like some input first.