FYNE List-Widget "list.OnSelected": check if CTRL-Key is pressed or not

[beckx75]

Hello community,

in my app i have a List.Widget containing Labels. For hours and hours i try to get it working, that the Callback OnSelected could check, if the CTRL-Key is pressed or not. If it is pressed, confirm action 1, if not - confirm action 2.

I've searched on the board for similar discussions - and i found some which are close enough to my problem i think.
I have to Extend the List-Widget.
My idea is, to check the OnKeyDown and OnKeyUp interfaces, to store if ctrl-key is pressed.
In "OnSelected" callback from list i check the variable and perform the actions.

I have also looked ad the fyne_demo-code - especially on advanced.go - but i can't figure out, how i can use the "OnKeyUp" and "OnKeyDown" funcs.

But i can't get it up and running - my currently now last version of the code (see below) won't compile with this errors :(

.\main.go:26:56: syntax error: unexpected { in parameter list; possibly missing comma or )
.\main.go:29:2: syntax error: unexpected } after top level declaration
.\main.go:31:54: syntax error: unexpected { in parameter list; possibly missing comma or )
.\main.go:34:2: syntax error: unexpected } after top level declaration

This is my code:

package main

import (
	"fmt"
	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/widget"
	"fyne.io/fyne/v2/container"
	// "fyne.io/fyne/v2/driver/desktop"
)

var ctrltapped bool

type mylist struct {
	widget.List
}

func newMylist(length func() int, createItem func() fyne.CanvasObject, updateItem func(id widget.ListItemID, item fyne.CanvasObject)) *mylist {
	l := &mylist{}
	l.Length = length
	l.CreateItem = createItem
	l.UpdateItem = updateItem
	l.ExtendBaseWidget(l)
	return l
}
func (ml *mylist) SetOnKeyDown(func(ev *fyne.KeyEvent) {
	if (ev.Name == "LeftControl" {
		ctrltapped = true
	}
}){}
func (ml *mylist) SetOnKeyUp(func(ev *fyne.KeyEvent) {
	if (ev.Name == "LeftControl" {
		ctrltapped = false
	}
}){}

func (ml *mylist) OnKeyDown() func(*fyne.KeyEvent) {
	return nil
}

func (ml *mylist) OnKeyUp() func(*fyne.KeyEvent) {
	return nil
}

func main() {
	fmt.Println("starting gui")
	ctrltapped = false
	
	app := app.New()
	win := app.NewWindow("this is MRT...")

	data := []string{"eins", "zwei", "drei"}
	
	l := newMylist(
		func() int {
			return len(data)
		},
		func() fyne.CanvasObject {
			return widget.NewLabel("template")
		},
		func(id widget.ListItemID, o fyne.CanvasObject) {
			o.(*widget.Label).SetText(data[id])
		},
	)
	l.OnSelected = func(id widget.ListItemID) {
		// if (CTRL is HOLD DOWN) {
		if ctrltapped {
			fmt.Println("with ctrl")
		} else {
			fmt.Println("without CTRL down")
		}
	}

	mainbox := container.NewBorder(nil, nil, nil, nil,
		l,
	)

	win.SetContent(mainbox)
	win.CenterOnScreen()
	win.Resize(fyne.NewSize(1024, 760))
	win.ShowAndRun()
}

I've already read the "Extending Widgets"-Page on the fyne-homepage and thought i'ver understood, how it works. For Buttons and Labels i got some extensions to work - but not the solution for my "List"-Widget.

I'm confused and don't know what to do now - can somebody please help me or give me a hint what i have to do?

Bests
Beckx

[heejit]

try this ->

package main

import (
	"fmt"
	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/widget"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/driver/desktop"
)

var ctrltapped bool

type mylist struct {
	widget.List
}

func newMylist(length func() int, createItem func() fyne.CanvasObject, updateItem func(id widget.ListItemID, item fyne.CanvasObject)) *mylist {
	l := &mylist{}
	l.Length = length
	l.CreateItem = createItem
	l.UpdateItem = updateItem
	l.ExtendBaseWidget(l)
	return l
}

func main() {
	fmt.Println("starting gui")
	ctrltapped = false
	
	app := app.New()
	win := app.NewWindow("this is MRT...")

	data := []string{"eins", "zwei", "drei"}
	
	l := newMylist(
		func() int {
			return len(data)
		},
		func() fyne.CanvasObject {
			return widget.NewLabel("template")
		},
		func(id widget.ListItemID, o fyne.CanvasObject) {
			o.(*widget.Label).SetText(data[id])
		},
	)
	l.OnSelected = func(id widget.ListItemID) {
		// if (CTRL is HOLD DOWN) {
		if ctrltapped {
			fmt.Println("with ctrl")
		} else {
			fmt.Println("without CTRL down")
		}
	}

	mainbox := container.NewBorder(nil, nil, nil, nil,
		l,
	)
        
	// copied from advance.go
	if deskCanvas, ok := win.Canvas().(desktop.Canvas); ok {
		deskCanvas.SetOnKeyDown(func(ev *fyne.KeyEvent) {
			println("KeyDown: "+string(ev.Name))
			ctrltapped = true
		})
		deskCanvas.SetOnKeyUp(func(ev *fyne.KeyEvent) {
			println("KeyUp  : "+string(ev.Name))
			ctrltapped = false
		})

	}

	win.SetContent(mainbox)
	win.CenterOnScreen()
	win.Resize(fyne.NewSize(1024, 760))
	win.ShowAndRun()
}

[beckx75]

Thank you for your answer! the part ...copied from advance.go... i've tried also. In this case, the KeyDown and KeyUp do not work anymore, if my List has the focus :(
So if i release the key - the status of ctrltapped is not updated and therefore the state is always true :(

[heejit]

only focus widget/window will receive the Keyboard events

[beckx75]

äh - ok... that seems my List-Widget is not a Focus-Widget... but i can use it on klick on it... now i'm confused more and more. But thanks for your hint!

[heejit]

when you click on a item in the list focus shift from List to the item (which you created in CreateItem function)

[beckx75]

ah understand - i don't get to the List-Widget, because there are the List-Items above it... got it, thx

[andydotxyz]

You don't need any extended or custom widgets and you don't need to register key handlers - just use the CurrentKeyModifiers call, for example:

	if desk, ok := driver.(desktop.Driver); ok {
		modifiers := desk.CurrentKeyModifiers()
		fmt.Println("Current modifiers:", modifiers)
	}

[beckx75]

Thank you for your time and answer! But i can't figure out how to use your hint :( . You wrote ...for example... - that means for me, i can't just use the code as you wrote it.

Never the less i tried it and got this error:
main.go:37:17: undefined: driver

Then i changed the import-package from fyne.io/fyne/v2/driver/desktop to fyne.io/fyne/v2/driver and got this error:
main.go:37:17: use of package driver not in selector

Then i tried to use my Window variable to get it running: if desk, ok:= win.(desktop.Canvas);... and got this error:
/main.go:38:21: desk.CurrentKeyModifiers undefined (type desktop.Canvas has no field or method CurrentKeyModifiers)

Then i tried to use my "app"-variable... if desk, ok:= app.(desktop.Canvas);... and got the same error:
/main.go:38:21: desk.CurrentKeyModifiers undefined (type desktop.Canvas has no field or method CurrentKeyModifiers)

Then i tried to use my List-variable: if desk, ok:= l.(desktop.Canvas);... (l is of type widget.List) and got this error:
./main.go:37:17: invalid operation: l (variable of type *"fyne.io/fyne/v2/widget".List) is not an interface

In the fyne_demo-github go-files i've look for "CurrentKeyModifiers" in advanced.go where the keystrokes are - but there isn't something about that....

Looking on "https://docs.fyne.io/api/v2.6/" and type CurrentKeyModifiers into the search-entry i got the desktop.Driver-site. There i can see, that type Driver is an interface. And there i can see the func CurrentKeyModifiers() funye.KeyModifier

I can understand, that the community here is annoyed by me, but i am really not able to figure out, how to use this :( - and i always thought i'm not stupid :(

So if someone reads this and knows how to handle it - please give me an answer!

Tanks for your patience and bests
Beckx

[andydotxyz]

In the code above driver is a variable that hits your app driver.

You could replace it with myapp.Driver() (assuming your app instance is a variable called myapp).

[beckx75]

how amazing - it works! Thx a lot! If someone is interested to the code i can paste it here! Thank you

[heejit]

yes pls do it may help someone else.

[beckx75]

Hope it will be usefull for someone else :)

package main

import (
	"fmt"

	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/driver/desktop"
	"fyne.io/fyne/v2/widget"
)

func main() {
	fmt.Println("starting gui")
	app := app.New()
	win := app.NewWindow("this is MRT...")

	desk, ok := app.Driver().(desktop.Driver)
	if !ok {
		panic("could not get desktop-driver for app!")
	}

	data := []string{"eins", "zwei", "drei"}

	l := widget.NewList(
		func() int {
			return len(data)
		},
		func() fyne.CanvasObject {
			return widget.NewLabel("template")
		},
		func(id widget.ListItemID, o fyne.CanvasObject) {
			o.(*widget.Label).SetText(data[id])
		},
	)
	l.OnSelected = func(id widget.ListItemID) {
		modifiers := desk.CurrentKeyModifiers()
		fmt.Println("Current Modifiers-Value:", modifiers)
	}

	mainbox := container.NewBorder(nil, nil, nil, nil,
		l,
	)

	win.SetContent(mainbox)
	win.CenterOnScreen()
	win.Resize(fyne.NewSize(1024, 760))
	win.ShowAndRun()
}

bests
Beckx