Add a "SimpleWidget" or "StaticRenderer" so I can make canvas primitives interactive

[andydotxyz]

Is your feature request related to a problem? Please describe:

The amount of code required to make a simple widget is high, especially if I just want to wrap an existing CanvasObject.

Is it possible to construct a solution with the existing API?

Yes, but it's a lot of code.

Describe the solution you'd like to see:

Something like the following would allow me to make a tappable image:

type tappableImage struct {
    SimpleWidget
}

func (t *tappableImage) Tapped(_ *PointEvent) {
... etc 
}

func newTappableImage(img *canvas.Image) *tappableImage {
    ret := &tappableImage{}
    ret.SimpleWidget := widget.NewSimpleWidget(img) 
    return ret
}

[gooid]

suggest:

index 9d021e03..ab37f920 100644
--- a/internal/painter/gl/draw.go
+++ b/internal/painter/gl/draw.go
@@ -153,5 +153,9 @@ func (p *glPainter) drawObject(o fyne.CanvasObject, pos fyne.Position, frame fyn
                p.drawGradient(obj, p.newGlRadialGradientTexture, pos, frame)
        case fyne.Widget:
                p.drawWidget(obj, pos, frame)
+       default:
+               if obj, ok := o.(interface{ superCanvas() fyne.CanvasObject }); ok {
+                       p.drawObject(obj.superCanvas(), pos, frame)
+               }
        }
 }

cmd/fyne_demo/main.go

// Package main loads a very basic Hello World graphical application.
package main

import (
	"fmt"

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

func main() {
	a := app.New()
	w := a.NewWindow("Hello")

	hello := widget.NewLabel("Hello Fyne!")
	w.SetContent(widget.NewVBox(
		hello,
		//widget.NewButton("Hi!", func() {
		NewCustomButton("Hi!", func() {
			hello.SetText("Welcome :)")
		}),
	))

	w.ShowAndRun()
}

type CustomButton struct {
	*widget.Button
}

func (button *CustomButton) superCanvas() fyne.CanvasObject {
	return button.Button
}

// MouseIn is called when a desktop pointer enters the widget
func (button *CustomButton) MouseIn(ev *desktop.MouseEvent) {
	fmt.Println("mouse in...", ev)
	button.Button.MouseIn(ev)
}

func NewCustomButton(text string, fn func()) *CustomButton {
	return &CustomButton{
		Button: widget.NewButton(text, fn),
	}
}

[andydotxyz]

The example you posted above is already supported - in your constructor function call ExtendBaseWidget() - the docs are at https://developer.fyne.io/tutorial/extending-widgets @gooid

[alkanna]

Hey @andydotxyz, I'm still looking for a solution to this. I'd simply like to create a custom image widget that I can regularly update. For the record, it would be a map tile that I would update based on the desired coordinates.
I tried to reimplement this by looking at how most internal widgets are currently implemented, by I hit a wall when trying to reimplement a renderer for my widget. It just feels like an insane amount of code just to get this working. I thought by extending BaseWidget I could get this in working order with minimal code addiitions, but it seems it's not possible yet, or I just can't see the obvious.

Anyone can help ?

[andydotxyz]

I don't think that what you described required a custom widget @alkanna - if you have a canvas.Image that you want to update, just apply the changes to it and call Refresh().
What else were you looking to do?

[alkanna]

I was looking into being able to inject additional sprites onto that image and draw them over it as I see fit

[andydotxyz]

Then perhaps container.NewMax(img1, img2, img3) so you can have 3 images on top of each other?
Or use a single Go image.Image and then draw it using canvas.NewImageFromImage?
Neither need custom widgets.

[andydotxyz]

This is now on develop :)