High CPU use when showing CustomDialogs

[dweymouth]

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

Showing a custom confirm dialog using dialog.ShowCustomConfirm uses high CPU while the dialog is displayed. After dismissing the dialog the CPU settles back down to normal.

How to reproduce

Run the example code, with an Activity Monitor/Task Manager/etc window open, and click the button to show the custom confirm dialog

Screenshots

No response

Example code

package main

import (
	"log"

	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/dialog"
	"fyne.io/fyne/v2/widget"
)

func main() {
	myApp := app.New()
	myWindow := myApp.NewWindow("Custom Confirm CPU bug")

	button := widget.NewButton("Show dialog", func() {
		dialog.ShowCustomConfirm("Custom confirm", "Confirm text", "Dismiss text",
			widget.NewLabel("Content"), func(b bool) {
				log.Printf("Confirm dismissed with value %v\n", b)
			}, myWindow)
	})
	myWindow.SetContent(container.NewCenter(button))
	myWindow.Resize(fyne.NewSize(400, 300))
	myWindow.ShowAndRun()
}

Fyne version

2.4.3

Go compiler version

go1.21.1

Operating system and version

macOS Ventura M2

Additional Information

No response

[dweymouth]

Reproes with dialog.ShowCustom too

[Jacalz]

Is this specific to custom dialogs or dialogs in general? I can’t think of anything specific that the custom ones do but the others don’t

[dweymouth]

Specific to custom dialogs. Regular ShowInformation, etc don't show the issue. I think it must be somehow related to the CustomDialog type itself

[Jacalz]

It is just a struct with a pointer to the good old dialog struct. Nothing special really. I'm not saying that you are wrong but I have a hard time seeing that it would be specific to custom only

[dweymouth]

Yeah I'm equally confused. Maybe it's a platform-specific thing too. Are you able to replicate it?

[Jacalz]

Just on my phone now, sorry. Can't guarantee when I can have a look

[vinser]

On my Ubuntu SBC your example code with it myWindow.Resize(fyne.NewSize(400, 300)) doesn't make CPU load

But if I stretch main window 1500x600 then it loads CPU high

[vinser]

Loads continuously

[vinser]

If you have some controls with data binding or OnChanged defined in dialog.NewCustomConfirm then high CPU load is guaranteed :)
It may be so high that bindings skip ticks IMO/ So I have to use OnChangeEnded instead of OnChanged for sliders.
I could of course be wrong about the reason

[vinser]

It seems that this bug is typical not only for complex CustomConfirm , but also for simpe CustomDialog which only displays some info

[vinser]

I tested my app on Windows PC. Here it is

When I open above dialog GPU consumption rises up to 42-43% (plateau under the red arrow).
On my Ubuntu SBC it loads CPU because GPU does not work.

[dweymouth]

Hmm sounds like a refresh loop where it's triggering redrawing on every frame

[Jacalz]

Are there any other dialogs that also show this behaviour? Form perhaps?

[vinser]

All my app dialogs (5 pieces) show this behavior except OpenFolder. Maybe because OpenFolder doesn't contain any other widgets.
Some of them are quite simple like Hot-keys list and the other like photo editor are as mini app

[vinser]

You can look at https://github.com/vinser/pixyne/blob/master/m_dialogs.go if you wish

[vinser]

Dialogs in fyne_demo works great - no high CPU load :)

[vinser]

All but custom dialogs of fyne_demo work great - no high CPU load. But this one do

func colorPicked(c color.Color, w fyne.Window) {
	log.Println("Color picked:", c)
	rectangle := canvas.NewRectangle(c)
	size := 2 * theme.IconInlineSize()
	rectangle.SetMinSize(fyne.NewSize(size, size))
	dialog.ShowCustom("Color Picked", "Ok", rectangle, w)
}

So it's not my app feature :)

[dweymouth]

So the one problematic dialog in fyne_demo is the single one that is created using dialog.NewCustom. More evidence that most dialogs are OK, it's just the CustomDialog type is somehow messed up

[andydotxyz]

Good find, I can confirm that the colour chosen dialog in fyne_demo causes high CPU here too!

It would appear that on every walk it is generating new image textures.
I think this could relate to dialogs having an image, and custom dialogs setting them to nil - perhaps it is a duplicate of #4345...

[andydotxyz]

I wonder if the following is a good solution? It doesn't seem to take the CPU usage to 0 though...

--- a/internal/painter/gl/draw.go
+++ b/internal/painter/gl/draw.go
@@ -36,6 +36,9 @@ func (p *painter) drawGradient(o fyne.CanvasObject, texCreator func(fyne.CanvasO
 }
 
 func (p *painter) drawImage(img *canvas.Image, pos fyne.Position, frame fyne.Size) {
+       if img.Image == nil && img.File == "" && img.Resource == nil || img.Translucency == 1.0 {
+               return
+       }
        p.drawTextureWithDetails(img, p.newGlImageTexture, pos, img.Size(), frame, img.FillMode, float32(img.Alpha()), 0)
 }

[dweymouth]

Good sleuthing @andydotxyz - if the image is really the root cause, it could be solved for dialogs without even solving #4345 by setting the dialog's image to Hidden whenever it is empty

[andydotxyz]

Good sleuthing @andydotxyz - if the image is really the root cause, it could be solved for dialogs without even solving #4345 by setting the dialog's image to Hidden whenever it is empty

Aha that is a much better plan :)

[andydotxyz]

Fixed on develop, we will pick it into v2.4.4 as well