Red pane after saving in editors

[SabineMa]

Bug description
After saving in any editor in Pharo 11, a part or the whole pane of the editor is red and this window can no longer be used. There was a discussion in Discord:
https://discord.com/channels/223421264751099906/278558427796602882/1164880827310669865
https://discord.com/channels/223421264751099906/278558427796602882/1166305029926420550

To Reproduce
Unfortunately not clear at the moment.
Possibly in conjunction with cmd-s for saving.

Expected behavior
No red window:-)

Screenshots

Version information:

• OS: Mac but also win -see discord
• Pharo Version 11

[SabineMa]

This is from Yanni:
yanni — gestern um 16:59 Uhr
I see the red box too. I'm on MacOS. It happened often prior to Pharo10. I was on Pharo10 for a long time (one year plus), and rarely saw the red box. After moving to Pharo11 a few months ago, I see it now and then (compared to almost never with Pharo10). It usually happens after a code change - I usually use cmd-S keyboard shortcut to save, not the menu. I try to avoid making code changes in the Debugger, because I've found that the change sometimes gets "lost" - i.e. proceeding from debugger fixes the problem, but when I browse the method from System browser, the code is nowhere to be found (not even in method version history).

My guess is that there is some timing issue with more than one process updating something, when a code change is saved - which leads to loss of code and/or redraw problems. My image had become sluggish recently, and I couldn't find any extra Process instances running, nor was the image extra big. But I was not getting red boxes when doing a code save. Instead, I got debugger windows with stacktrace in some window redraw code. I just closed the extra debugger. I still have that sluggish image, but the debugger would pop up now and then - no idea how to make it happen.

Norbert Hartl and Carlos reported that they have it, too.

[Rinzwind]

This seems closely related to issue #9638 for which a fix was committed in pull request #14853.

[MarcusDenker]

I backported two fixes, I don't think they are fixing this problem, but for sure nice to have:

#15374
#15373

[astares]

I only had this issue in the debugger editing pane when clicking too fast, was easy to patch - but this is solved with backport of #15372.

Any chance to put a one time halt into one of the drawing methods and try to debug the case?

[tinchodias]

I agree with with @Rinzwind that this could be fixed by enclosing some code into a defer: [ ... ] as in #14853.
The cause might be that a "non-ui process" mutates the Calypso morph in an unexpected point of the "ui process".