Launchers

A launcher, as Spotlight, Raycast, Alfred, PowerToys Run or Ulauncher, is summoned from anywhere with a keyboard shortcut, takes what the user types over the app they are in, and goes away as fast as it came. MyGo has the parts: a panel to show it in, a global shortcut to summon it, the installed apps and their icons to search, and an app without a Dock icon that lives in the tray. examples/launcher puts them together in native UI:

go run ./examples/launcher

An app in the background

A launcher has no Dock icon and no entry in the app switcher, runs with no window showing, and runs once:

func main() {
	if !mygo.App.RequestSingleInstanceLock() {
		return // the launcher that runs shows itself
	}
	mygo.App.SetActivationPolicy(mygo.ActivationPolicyAccessory)
	mygo.App.OnWindowAllClosed(func() {})
	mygo.App.OnSecondInstance(func([]string, string) { show() })
	mygo.App.WhenReady(ready)
	if err := mygo.App.Run(); err != nil {
		log.Fatal(err)
	}
}

A packaged app says it from the start, so that macOS never shows it in the Dock, with LSUIElement in mygo.json:

{
  "macos": { "infoPlist": { "LSUIElement": true } }
}

A tray icon gives the user a way in other than the shortcut, and to quit; App.SetOpenAtLogin starts the launcher with the session, and App.WasOpenedAtLogin tells it to stay hidden then.

The panel

A panel floats above every app, full-screen ones too, on whichever Space or virtual desktop the user is on, and on macOS takes the keyboard without activating the launcher: the app the user was in keeps its menu bar, and has the keyboard back once the panel hides. Create it hidden, once, and hide it rather than close it, so that it shows again at once, as it was:

panel := mygo.NewWindow(mygo.WindowOptions{
	Panel:         true,
	Hidden:        true,
	Frameless:     true,
	Transparent:   true,
	Vibrancy:      mygo.VibrancyPopover, // Acrylic on Windows 11
	Width:         680,
	Height:        420,
	DisableResize: true,
	Content:       ui.View(app.view), // or URL: "/launcher"
})
panel.OnClose(func(e *mygo.CloseEvent) { // Escape, Cmd-W, Alt-F4
	e.PreventDefault()
	panel.Hide()
})
panel.OnBlur(panel.Hide) // the user went elsewhere

An Escape that the page or native UI leaves closes a panel, which the OnClose listener turns into hiding it. Handle Escape yourself where it does something first, as clearing the query does in the example.

Show it on the display the user is looking at, which the pointer tells, a third of the way down as Spotlight does, and give its search field the keyboard:

func show() {
	d := mygo.Screen.DisplayNearestPoint(mygo.Screen.CursorScreenPoint())
	w, h := panel.Size()
	panel.SetPosition(d.WorkArea.X+(d.WorkArea.Width-w)/2, d.WorkArea.Y+(d.WorkArea.Height-h)/3)
	app.query = ""
	app.input.Focus()
	panel.Show()
}

The shortcut

err := mygo.GlobalShortcut.Register("Alt+Shift+Space", func() {
	if panel.IsVisible() {
		panel.Hide()
	} else {
		show()
	}
})

Pick one other launchers leave free: Raycast and PowerToys Run take Alt+Space, Spotlight Cmd+Space, and macOS gives a shortcut to every app that registers it, so both would open. Let the user choose another in the launcher's settings: Unregister the old one and Register the new one, and tell them when Register fails because it is taken. On Windows the key press lets the panel take the foreground; on Wayland the desktop binds the shortcut, see global shortcuts.

Finding apps

Shell.InstalledApps lists the applications installed on the computer, sorted by name, with the names the system shows in the user's language. It reads the disk, in tens of milliseconds: list them on a goroutine as the panel shows, and hand them to the view with Window.Update (or to the page through a bound service):

go func() {
	apps, err := mygo.Shell.InstalledApps()
	if err != nil {
		log.Print(err)
	}
	panel.Update(func() {
		app.apps = apps
		app.filter()
	})
}()

Shell.FileIcon(app.Path, size) draws an app's icon as a PNG, in pixels: the size in DIPs times the scale factor of the display. It takes a few milliseconds: draw the icons of the rows that show, and keep them by path. Shell.LaunchApp(app) starts the chosen app, or brings it to the front; hide the panel first, so that the app the user was in has the keyboard until the launched one takes it.

Platforms

On Wayland, a panel that is a layer surface keeps the keyboard while it shows, as launchers there do, so it is blurred only as it hides: close it on Escape.