example/gui-linux does not exit when vm.Stop() is used

[cfergeau]

Describe the bug
The GUI code in virtualization_view.m is notified when there was a guest initiated shutdown ('guestDidStopVirtualMachine') and when there was a virtualization error ('didStopWithError').

When calling Stop(), the VM is forcefully stopped (similar to pulling the plug on real hardware). This action is neither a guest initiated shutdown, nor a virtualization error, so the GUI code does not catch it. This means after calling vm.Stop(), the GUI main loop will keep running, and the application using Code-Hex/vz will never exit.

The branch https://github.com/cfergeau/vz/tree/hardstop-gui has a fix for this bug. It adds an observer for VM state changes, and calls 'terminate' when the VM state becomes 'stopped' or 'error'.

I can file a PR if this approach is acceptable to you, or I can explore a different fix if needed.

This was initially reported as crc-org/vfkit#67

To Reproduce
Steps to reproduce the behavior:

1. Apply this patch

diff --git a/example/gui-linux/main.go b/example/gui-linux/main.go
index 5db3f99..b98bdd7 100644
--- a/example/gui-linux/main.go
+++ b/example/gui-linux/main.go
@@ -77,6 +77,17 @@ func run(ctx context.Context) error {
                }
        }()
 
+       go func() {
+               if !vm.CanStop() {
+                       log.Println("cannot stop vm forcefully")
+                       return
+               }
+               time.Sleep(10 * time.Second)
+               log.Println("calling vm.Stop()")
+
+               vm.Stop()
+       }()
+
        // cleanup is this function is useful when finished graphic application.
        cleanup := func() {
                for i := 1; vm.CanRequestStop(); i++ {

(this change is made in my branch https://github.com/cfergeau/vz/tree/hardstop-gui)

2. Start gui-linux

Expected behavior

The process stops after 10 seconds.

Environment that you use to compile (please complete the following information):

• macOS Version: [sw_vers | pbcopy]

ProductVersion:		13.6.1
BuildVersion:		22G313

• mac architecture: [uname -m | pbcopy] arm64
• Go Version: [go version | pbcopy] go version go1.20.5 darwin/arm64

[Code-Hex]

@cfergeau Sorry, what was the problem with this issue?
Is the problem that calling stop does not stop the GUI event loop? I assume that clicking close exits the application, but is that not good enough?

[cfergeau]

@cfergeau Sorry, what was the problem with this issue? Is the problem that calling stop does not stop the GUI event loop? I assume that clicking close exits the application, but is that not good enough?

Yes, calling vm.Stop() does not exit the event loop. This is different behaviour from what happens if it is the guest which shuts down (ie vm.RequestStop()). Clicking close exits the application, but I want to do close the window programmatically. The window is only used to show a debug console for display purpose, it's unexpected that in some cases the user has to close this debug console to be able to exit the command line application.

[Code-Hex]

@cfergeau Thank you for your explanation. I'll fix it in the PR I'm currently opening.

Clicking close exits the application, but I want to do close the window programmatically.

[Code-Hex]

@cfergeau Could you check this comment please 🙏
#173 (comment)