richImage may freeze the application in some cases.

[alexballas]

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

I have an application where in one tab I have some richtext with an image and in another tab I have a drop down menu where you can select different themes for the application. If I open the application for the first time and I DONT click on the tab that has the rich text, I can change the theme from the other tab without issues, consistently.
If I click on the richtext tab and go back to select the theme from the dropdown, the application might freeze after I choose a theme. (this is intermittent behaviour)

So this is what happens when I select a theme

1. (c *glCanvas) MinSize() calls RLock and then c.canvasSize(c.content.MinSize())
2. The type of c.content in this case is container.AppTabs
3. (t *AppTabs) MinSize() calls t.BaseWidget.MinSize().
4. The type of BaseWidget is *widget.textRenderer
5. inside (r *textRenderer) MinSize() there is a for loop for range bound.segments. One of the objects in that loop is widget.richImage
6. (r *richImage) MinSize() calls internal.ScaleInt(c, orig.Width)
7. internal.ScaleInt calls c.Scale(). c is a fyne.Canvas interface which with reflect I checked that is the glfw.glCanvas type.
8. (c *glCanvas) Scale() calls RLock

Step 8 tries to get RLock but step 1 has not released it yet.

I managed to replicate the same issue in a much simpler example. Please check the provided code below. The application will freeze after a few seconds.

How to reproduce

Refer to the Go code below.

Screenshots

No response

Example code

package main

import (
	"time"

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

var currentmfolder string

func main() {

	myApp := app.New()
	myWindow := myApp.NewWindow("Test Dialog")
	l := widget.NewLabel("hello")
	rich := widget.NewRichTextFromMarkdown(`![test](SOME_IMAGE_HERE.png)`)
	cont := container.NewVBox(l, rich)
	myWindow.SetContent(cont)

	go func() {
		for i := 0; i < 1000; i++ {
			go func() { fyne.CurrentApp().Settings().SetTheme(theme.DarkTheme()) }()
			time.Sleep(500 * time.Millisecond)
			go func() { fyne.CurrentApp().Settings().SetTheme(theme.LightTheme()) }()
			time.Sleep(500 * time.Millisecond)
		}
	}()

	myWindow.ShowAndRun()
}

Fyne version

v2.3.0

Go compiler version

1.19.4

Operating system

Linux

Operating system version

Ubuntu 18.04

Additional Information

No response

[andydotxyz]

We think this was fixed, does it look good to you @alexballas ?

[alexballas]

Hello @andydotxyz, I can still replicate the issue with 2.4.0