Bug or Quirk

[TimStreater]

Some testing here reveals it happens on mouseDown, but not on mouseEnter or mouseUp. In both the latter two cases, the window closes, end of story. Xojo 2023 r1.1 under macOS Catalina.

[Barry_Sidebottom]

Hey guys, thanks for the interest, I’m going to bow out now. It was only a quirk that I found this as I don’t usually call the Close from the rectangle anyway.
You’ve given me something to tinker with tho, I’ll have a look at canvases as another way to do this. I’ll leave the technical riddle of this issue to you guys

Barry

[Julia_Truchsess]

I have a similar issue with 2021r2.1 if I call App.Quit while a window opened via MouseDown on a GroupBox is still open. I can close the window without error but quitting the app with that window open crashes every time. My workaround is to close the window, if open, in App.CancelClose.

[Beatrix_Willius]

Finding bugs comes from “oh, that looks odd”.

[Jürg_Otter]

@Barry_Sidebottom

Rectangle1.MouseDown
Window1.Close

Just wondering if this is a bug or a quirk or just something I don’t understand.

Both a bug and a quirk

The bug is this (and could/should be reported, just in case):

@Greg_O

I would say, based on the type of crash, that this is the Xojo framework trying to access a recently freed pointer. That is, events are probably being scheduled before the window closes and then fire for something that no longer exists.
…
it’s possible that it has to do with the fact that it’s a rectangle vs a control as technically a rectangle isn’t a control, but a decoration and the underlying OS hierarchy is different

The crash / stack trace very much looks like this.
Certainly something that Xojo could fix.

I agree that MouseDown is the wrong place for actions (and it would even “magically fix” this bug if you’d close the Window in MouseUp)… because:

@TimStreater

Personally I use MouseUp for the actual work of the button, as it affords the user, having pressed the mouse in the button, the chance to slide the mouse off trhe button and then release the mouse, without the action being done.

And to finish why I agree that it’s both bug (see above) and a quirk:

@Barry_Sidebottom

It was only a quirk that I found this as I don’t usually call the Close from the rectangle anyway.

Over the years I came across quite some issues when trying to do things like this in (Mouse) Events. Another one is showing a Modal Dialog out of these places. Sometimes it’s a macOS-issue, others Windows-issues.
In short: One shouldn’t do “blocking” or “destroying” things in these (Mouse / Key) Events.

Especially when Events come in pairs, such as MouseDown → MouseUp.
Again: Actions in MouseUp. MouseDown is just to return true if you intend to handle the MouseUp Event in your code.
Just try to think that these two events belong together. It doesn’t make sense to “remove” the Window/Control when it is expected that the second Event will/should happen later.

And for those rare and “to be avoided” cases the “ugly workaround” would be to schedule your action a tiny bit later (in a different RunLoop) e.g. by using a Timer:

Function MouseDown(x As Integer, y As Integer) Handles MouseDown as Boolean
  Timer.CallLater(1, AddressOf Self.Close)
  Return True
End Function

Sub MouseUp(x As Integer, y As Integer) Handles MouseUp
  ' Empty 
End Sub