To build our first qt application with Go, let's make another Hello World application. As with previous examples, we'll make use of a simple vertical box layout within a single application window. The following code should be sufficient to load your first application:

package main

import (
   "os"

   "github.com/therecipe/qt/widgets"
)

func main() {
   app := widgets.NewQApplication(len(os.Args), os.Args)

   window := widgets.NewQMainWindow(nil, 0)
   window.SetWindowTitle("Hello World")

   widget := widgets.NewQWidget(window, 0)
   widget.SetLayout(widgets.NewQVBoxLayout())
   window.SetCentralWidget(widget)

   label := widgets.NewQLabel2("Hello World!", window, 0)
   widget.Layout().AddWidget(label)

   button := widgets.NewQPushButton2("Quit", window)
   button.ConnectClicked(func(bool) {
      app.QuitDefault()
   })
   widget.Layout().AddWidget(button)

   window.Show()
   widgets.QApplication_Exec()
}

Let's note a few details from this code snippet. You'll see that each of the widget constructor functions takes (typically) two parameters, each is the parent widget and a flags parameter. Additional types passed in will usually be added before these values with a note in the function name that there are additional parameters. For example, widgets.NewQLabel2(title, parent, flags) is equivalent to widgets.NewQLabel(parent, flags).SetTitle(title). Additionally, you'll see that the layout is applied to a new widgets.QWidget through SetLayout(layout), and that's set to the window content through window.SetCentralWidget(widget).

To load the display and run the application, we call window.Show() and then widgets.QApplication_Exec(). This file is built in the usual way with go build hello.go:

The file built is quite large due to the size of the Qt framework. This will be reduced significantly when packaging for a specific distribution. This topic will be covered in depth in Chapter 14, Distributing your Application.