What's wrong with this Extended Slider?

[lordofscripts]

I was trying to bind the mousewheel (mouse scrollwheel) to increase/decrease the slider. It appears to work partly. For one thing, I don't know whether that 25 DY is always the same across platforms.

But my main issue with it is that if you move forward/backward, at some point you see that the value isdecreased but the visual ball on the slider actually decreases.

import (
	"fmt"

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

type ScrollableSlider struct {
	*widget.Slider

	OnScrolled func(*fyne.ScrollEvent)
}

func NewScrollableSlider(min, max float64) *ScrollableSlider {
	ss := &ScrollableSlider{
		Slider: widget.NewSlider(min, max),
	}

	return ss
}

func NewScrollableSliderWidthData(min, max float64, data binding.Float) *ScrollableSlider {
	ss := &ScrollableSlider{
		Slider: widget.NewSliderWithData(min, max, data),
	}

	return ss
}

// implements fyne.Scrollable
func (g *ScrollableSlider) Scrolled(event *fyne.ScrollEvent) {
	// @note FWD scroll gives Dx:0 Dy:25 and BACK scroll Dx:0 Dy:-25
	// I wonder if that 25 is the same for all platforms or does it vary?
	const DIVIDER int = 25
	// dx := int(float64(event.Scrolled.DX))
	dy := int(float64(event.Scrolled.DY)) / DIVIDER
	//fmt.Printf("Slider mousewheel dX:%d dY:%d\n", dx, dy)

	newValue := g.Value + float64(dy)
	if newValue > g.Max {
		newValue = g.Max
	} else if newValue < g.Min {
		newValue = g.Min
	}
	fmt.Printf("Slider mousewheel dY:%d new:%f\n", dy, newValue)
	g.SetValue(newValue)
	g.Refresh()
}

[dweymouth]

Two things:

1. you forgot to call ExtendBaseWidget
2. you should embed widget.Slider, not *widget.Slider

So it should look something like:

type ScrollableSlider struct {
	widget.Slider   // removed pointer embed

	OnScrolled func(*fyne.ScrollEvent)
}

func NewScrollableSlider(min, max float64) *ScrollableSlider {
	ss := &ScrollableSlider{
		Slider: widget.Slider{Min: min, Max: max), // init base struct directly
	}
	ss.ExtendBaseWidget(ss) // need this to set up extension correctly

	return ss
}

[lordofscripts]

Much appreciated 👍🏻 A further enhanced version is now available on my Go-Fynex Go/Fyne extensions module.