Golang : Qt progress dialog example

Found a need to show progress indication while developing a Qt application recently. Below is a simple example of how to invoke the Qt ProgressDialog in Golang with Qt-binding.

What it does is to launch a GUI application with a button to press. Upon pressing the button, you will see a progress dialog box in action and show the text update on your terminal screen.

Please follow the setup instruction for Golang-Qt bindings at https://github.com/therecipe/qt

Tips: Dump out the documentation to text files for easier search and viewing.

 $godoc github.com/therecipe/qt/widgets > widgets.txt

 $godoc github.com/therecipe/qt/gui > gui.txt

 $godoc github.com/therecipe/qt/core > core.txt

Here you go!

 package main

 import (
 "fmt"
 "github.com/therecipe/qt/core"
 "github.com/therecipe/qt/widgets"
 "os"
 "time"
 )

 var (
 mainApp *widgets.QApplication
 progressDialog *widgets.QProgressDialog
 mainLayout *widgets.QWidget
 )

 func delaySecond(n time.Duration) {
 time.Sleep(n * time.Second)
 }

 func populate() *widgets.QWidget {

 mainLayout = widgets.NewQWidget(nil, 0)
 button := widgets.NewQPushButton2("Show Progress Dialog", nil)
 button.ConnectClicked(func(flag bool) {

 jobs := 100
 progressDialog := widgets.NewQProgressDialog(mainLayout, core.Qt__Widget)
 progressDialog.SetWindowModality(core.Qt__NonModal)
 progressDialog.SetWindowTitle("Progress bar progressing...")
 progressDialog.SetMinimum(0)
 progressDialog.SetMaximum(jobs)
 progressDialog.Show()

 for i := 1; i < jobs; i++ {
 progressDialog.SetValue(i)

 // see http://stackoverflow.com/questions/8399349/simple-example-using-qprogressdialog-any-ideas-why-this-doesnt-work-properly
 // on the QApplication::processEvents()

 // somehow ExcludeUserInputEvents will prevent us from clicking the Cancel button!
 //core.QCoreApplication_ProcessEvents(core.QEventLoop__ExcludeUserInputEvents)

 // without this line, the progress bar or UI elements will not be updated!!
 core.QCoreApplication_ProcessEvents(core.QEventLoop__AllEvents)

 // too fast! introduce some delay to let you see the progression
 delaySecond(time.Duration(1))

 if progressDialog.WasCanceled() {
 fmt.Printf("\r")
 fmt.Printf("\rAborted at %d/%d", i, jobs)
 break
 }

 // too lazy to add text label in the widget
 // so, we use https://www.socketloop.com/tutorials/golang-overwrite-previous-output-with-count-down-timer
 fmt.Printf("\rProgressing %d/%d", progressDialog.Value(), jobs)
 }
 progressDialog.SetValue(jobs)

 })

 layout := widgets.NewQVBoxLayout()
 layout.AddWidget(button, 0, core.Qt__AlignCenter)
 mainLayout.SetLayout(layout)
 return mainLayout
 }

 func main() {

 mainApp = widgets.NewQApplication(len(os.Args), os.Args)

 populate().Show()

 mainApp.Exec()
 }

References:

http://www.bogotobogo.com/Qt/Qt5QProgressDialogModalModelessQTimer.php

http://doc.qt.io/qt-5/qprogressdialog.html

http://stackoverflow.com/questions/25966730/how-can-i-add-a-progress-bar-in-splash-screen-pyqt4