Entry does not show the last (few) changes when updating a binding.String in a fast succession

[Roemer]

Checklist

• I have searched the issue tracker for open issues that relate to the same problem, before opening a new one.
• This issue only relates to a single bug. I will open new issues for any other problems.

Describe the bug

As discussed in Slack (https://gophers.slack.com/archives/CB4QUBXGQ/p1689959990702439) there seems to be an issue when a binding.String is bound to an Entry and is quickly updated multiple times. In that case, the Entry does not get all the last changes until the binding is updated again.

How to reproduce

1. Run the example code from below
2. Have a look at the Window (and optionally the terminal output). Theoretically it should display a and b randomly counting from 0 to 19. But you will just see a nothing or a few entries. Then after 5 seconds, it will add a final string and suddenly renders all missing parts.

Screenshots

Example code

package main

import (
	"fmt"
	"strconv"
	"time"

	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/data/binding"
	"fyne.io/fyne/v2/widget"
)

func main() {
	a := app.New()
	w := a.NewWindow("Test")
	w.Resize(fyne.NewSize(700, 300))

	textBinding := binding.NewString()
	widget := widget.NewEntryWithData(textBinding)

	logChannel := make(chan string, 100)
	go func() {
		for text := range logChannel {
			fmt.Println(text)
			existingText, _ := textBinding.Get()
			fmt.Println(existingText)
			newText := existingText + "," + text
			textBinding.Set(newText)
		}
	}()

	go func() {
		time.Sleep(time.Second * 1)
		for i := 0; i < 20; i++ {
			text := "a" + strconv.Itoa(i)
			logChannel <- text
			time.Sleep(time.Millisecond * 1)
		}
	}()
	go func() {
		time.Sleep(time.Second * 1)
		for i := 0; i < 20; i++ {
			text := "b" + strconv.Itoa(i)
			logChannel <- text
			time.Sleep(time.Millisecond * 1)
		}
	}()

	go func() {
		time.Sleep(time.Second * 5)
		logChannel <- "final"
	}()

	w.SetContent(widget)
	w.CenterOnScreen()
	w.ShowAndRun()
}

Fyne version

v2.3.6-0.20230720061213-19e0c73660eb

Go compiler version

1.20.6

Operating system and version

Linux WSL2, Windows 10

Additional Information

No response

[Roemer]

Probably related:
When then Entry contains a placeholder, a Set on the binding also seems not to work (at all or at least reliable).
See this example:

package main

import (
	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/data/binding"
	"fyne.io/fyne/v2/layout"
	"fyne.io/fyne/v2/widget"
)

func main() {
	a := app.New()
	w := a.NewWindow("Test")
	w.Resize(fyne.NewSize(700, 300))

	// Username
	sshUsernameBinding := binding.NewString()
	sshUsernameControl := widget.NewEntryWithData(sshUsernameBinding)
	sshUsernameControl.SetPlaceHolder("Username")
	sshUsernameBinding.Set("Test")

	w.SetContent(container.New(layout.NewFormLayout(), widget.NewLabel("Username"), sshUsernameControl))
	w.CenterOnScreen()
	w.ShowAndRun()
}

[Jacalz]

I think this might have been fixed on the develop branch. Would someone like to test?

[dan-frohlich]

Is this related to #4061 ?

[williambrode]

This is still happening on 2.4.3. Here is my test case where you can't get the widget to show the value "2" using the button. I think its a pretty big regression of the Entry widget with a binding - since the value shown to the user is wrong in many cases. I may have to revert back to before the bug on my project or use a different widget.

package main

import (
	"time"

	fyne "fyne.io/fyne/v2"
	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/data/binding"
	"fyne.io/fyne/v2/widget"
)

func main() {
	fyneApp := app.NewWithID("TestApp")

	win := fyneApp.NewWindow("TestWindow")
	win.Resize(fyne.NewSize(500, 500))
	boundString := binding.NewString()
	win.SetContent(
		container.NewVBox(
			widget.NewEntryWithData(boundString),
			widget.NewButton("change", func() {
				_ = boundString.Set("1")
				time.Sleep(10 * time.Millisecond)
				_ = boundString.Set("2")
			}),
		),
	)
	win.Show()

	fyneApp.Run()
}

[andydotxyz]

fixed on develop, will pick into 2.4.4