CompletionEntry cannot type word when SetText is called in widget.List

[BabySid]

As the following code shows, the text in CompletionEntry cannot be edited.

Screenshots

Steps to reproduce the behaviour:

• Run the code below

package main

import (
	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/widget"
	x "fyne.io/x/fyne/widget"
)

var data = []string{"a", "string", "list"}
var option = []string{"option1", "option2", "option3"}

func main() {
	myApp := app.New()
	myWindow := myApp.NewWindow("List Widget")

	list := widget.NewList(
		func() int {
			return len(data)
		},
		func() fyne.CanvasObject {
			return x.NewCompletionEntry(option)
		},
		func(i widget.ListItemID, o fyne.CanvasObject) {
			e := o.(*x.CompletionEntry)
			e.SetText(data[i])
			e.OnChanged = func(s string) {
				e.ShowCompletion()
			}
		})

	myWindow.SetContent(list)
	myWindow.ShowAndRun()
}

[BabySid]

After debugging, I found that whenever I input in the input box, the widget.List.UpdateItem is also called, so the completionentry.text is set back.
It is not clear for me why UpdateItem is called now.

[andydotxyz]

It is not clear for me why UpdateItem is called now.

It will be called at least whenever a cell may need to be refreshed (usually due to re-use, for example if list scrolls).
Additionally it will be called if something calls List.Refresh().

Essentially the problem is that you are mutating data that is being re-loaded from static data.
If however you updated your data source on edit (by setting the variable, or by using data binding) the issue would be resolved.

[BabySid]

Referring to your suggestion, I re implemented the code. But when I specified the method OnChange, the program crashed.

I debuged the code, and found:

func (c *CompletionEntry) maxSize() fyne.Size {
	cnv := fyne.CurrentApp().Driver().CanvasForObject(c) // cnv is nil
        ...
}

The demo code is as beblow:

import (
	"fmt"
	"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"
	x "fyne.io/x/fyne/widget"
)

var option = []string{"option1", "option2", "option3"}

func main() {
	myApp := app.New()
	myWindow := myApp.NewWindow("List Data")

	data := binding.BindStringList(
		&[]string{"Item 1", "Item 2", "Item 3"},
	)

	list := widget.NewListWithData(
		data,
		func() fyne.CanvasObject {
			return x.NewCompletionEntry(option)
		},
		func(i binding.DataItem, o fyne.CanvasObject) {
			e := o.(*x.CompletionEntry)
			e.Bind(i.(binding.String))
			e.OnChanged = func(s string) {
				e.ShowCompletion()
			}
		})

	add := widget.NewButton("Append", func() {
		val := fmt.Sprintf("Item %d", data.Length()+1)
		data.Append(val)
	})

	myWindow.SetContent(container.NewBorder(nil, add, nil, nil, list))
	myWindow.CenterOnScreen()
	myWindow.Resize(fyne.NewSize(600, 400))
	myWindow.ShowAndRun()
}

[BabySid]

Essentially the problem is that you are mutating data that is being re-loaded from static data.
If however you updated your data source on edit (by setting the variable, or by using data binding) the issue would be resolved.

I think the problem should still be on the CompletionEntry component. Because I replace with widget.SelectEntry, the issue is resolved.

[andydotxyz]

That it works this way with a SelectEntry is more luck than anything. You are applying a static data source to a dynamic item of data, this mismatch may or may not cause problems but either way it is a race condition in your code.

You mentioned that the updated code crashes - can you provide the crash log and the replication steps that led to it please?

[BabySid]

You mentioned that the updated code crashes - can you provide the crash log and the replication steps that led to it please?

To Reproduce:

Steps to reproduce the behaviour:

• Run the code below:

Crash Log

GOROOT=D:\ProgramFiles\go1.17.5 #gosetup
GOPATH=C:\Users\sid\go #gosetup
D:\ProgramFiles\go1.17.5\bin\go.exe build -o D:\projects\go-fyne\output\go_build_go_fyne.exe . #gosetup
D:\projects\go-fyne\output\go_build_go_fyne.exe
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0xa8 pc=0xc03f25]

goroutine 9 [running]:
fyne.io/x/fyne/widget.(*CompletionEntry).maxSize(0xc000332400)
        C:/Users/sid/go/pkg/mod/fyne.io/x/[email protected]/widget/completionentry.go:91 +0xe5 
fyne.io/x/fyne/widget.(*CompletionEntry).ShowCompletion(0xc000332400)
        C:/Users/sid/go/pkg/mod/fyne.io/x/[email protected]/widget/completionentry.go:76 +0x1be
main.main.func2.1({0xc000332400, 0xc00008fe60})
        D:/projects/go-fyne/main.go:32 +0x1d
fyne.io/fyne/v2/widget.(*Entry).updateText(0xc000332400, {0xfb0a80, 0x6})
        C:/Users/sid/go/pkg/mod/fyne.io/fyne/[email protected]/widget/entry.go:1179 +0x9f
fyne.io/fyne/v2/widget.(*Entry).SetText(0xc000332400, {0xfb0a80, 0xc0000520a0})
        C:/Users/sid/go/pkg/mod/fyne.io/fyne/[email protected]/widget/entry.go:457 +0x25
fyne.io/fyne/v2/widget.(*Entry).updateFromData(0xc000332400, {0x1068178, 0xc0000520a0})
        C:/Users/sid/go/pkg/mod/fyne.io/fyne/[email protected]/widget/entry.go:1124 +0xc5
fyne.io/fyne/v2/widget.(*basicBinder).Bind.func1()
        C:/Users/sid/go/pkg/mod/fyne.io/fyne/[email protected]/widget/bind_helper.go:25 +0xa2
fyne.io/fyne/v2/data/binding.(*listener).DataChanged(0x1)
        C:/Users/sid/go/pkg/mod/fyne.io/fyne/[email protected]/data/binding/binding.go:55 +0x1a
fyne.io/fyne/v2/data/binding.queueItem.func1.1()
        C:/Users/sid/go/pkg/mod/fyne.io/fyne/[email protected]/data/binding/queue.go:19 +0x42
created by fyne.io/fyne/v2/data/binding.queueItem.func1
        C:/Users/sid/go/pkg/mod/fyne.io/fyne/[email protected]/data/binding/queue.go:17 +0x45

Process finished with the exit code 2

Example Code

package main

import (
	"fmt"
	"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"
	x "fyne.io/x/fyne/widget"
)

var option = []string{"option1", "option2", "option3"}

func main() {
	myApp := app.New()
	myWindow := myApp.NewWindow("List Data")

	data := binding.BindStringList(
		&[]string{"Item 1", "Item 2", "Item 3"},
	)

	list := widget.NewListWithData(
		data,
		func() fyne.CanvasObject {
			return x.NewCompletionEntry(option)
		},
		func(i binding.DataItem, o fyne.CanvasObject) {
			e := o.(*x.CompletionEntry)
			e.Bind(i.(binding.String))
			e.OnChanged = func(s string) {
				e.ShowCompletion()
			}
		})

	add := widget.NewButton("Append", func() {
		val := fmt.Sprintf("Item %d", data.Length()+1)
		data.Append(val)
	})

	myWindow.SetContent(container.NewBorder(nil, add, nil, nil, list))
	myWindow.CenterOnScreen()
	myWindow.Resize(fyne.NewSize(600, 400))
	myWindow.ShowAndRun()
}