Infinite loop occurs when using LEAVE trigger and MESSAGE box in combination.

An infinite loop may occur in an application which uses multiple embedded windows. 

The loop may occur when a LEAVE trigger executes the RETURN NO-APPLY statement after displaying a message in an alert box.

Removing RETURN NO-APPLY prevents the issue but is used intentionally as part of the application's design.

Setting EmbeddedWinLeaveFix=NO prevents the loop but also appears to disable the LEAVE event since no messages are displayed.

Application features:

- an ABL .NET form.
- 2x WindowContainer controls for embedding ABL windows.

Each WindowContainer control has an embedded ABL window that has a fill-in with a LEAVE trigger.

The LEAVE trigger contains the code similar to the following:

MESSAGE "Leave" VIEW-AS ALERT-BOX.
RETURN NO-APPLY.

Clicking in the fill-in of the first fill-in in the first WindowsContainer, then clicking in the fill-in in the second WindowsContainer results in an infinite loop when the "Leave" message is displayed over and over.

The loop occurs due to the following sequence of events:

There are 2 window containers (siblings) and each contains an embedded window with a FILL-IN. Focus is in FILL-IN-1 in WindowContainer1 and FILL-IN-1 has a LEAVE trigger which executes RETURN NO-APPLY.

1) Focus is set to FILL-IN-1.
2) User clicks on FILL-IN-2 in the window embedded in WindowContainer2.
3) FILL-IN-2 gets a WM_SETFOCUS event. The User Interface Manager determines that FILL-IN-1 should receive a LEAVE event and fires the LEAVE trigger.
4) The LEAVE trigger displays a message box, taking focus away from FILL-IN-2.
5) When the message box is dismissed, Windows puts focus back on FILL-IN-2. When the WM_SETFOCUS message for FILL-IN-2 is received, focus is set to WindowContainer2.
6) GotFocus event handler of WindowContainer2 fires and call its changeFocus method via a delegate; changeFocus will propagate focus to FILL-IN-2, but is delayed because of the delegate.
7) The LEAVE trigger finishes. Since there was a RETURN NO-APPLY, focus is set to FILL-IN-1 (where it was before the trigger fired).
8) The changeFocus method is executed to set focus to the widget that last had focus in WindowContainer2: FILL-IN-2.
9) Setting focus to FILL-IN-2 leads back to step #2 and results in the infinite loop.

Upgrade to 11.5.1.

The undocumented EmbeddedWinLeaveFix=no parameter was introduced to disable the fix for defect PSC00278696. The parameter can be set in the Startup section of the registry or .ini file. The parameter should only be used when checking / testing focus issues and should not be implemented by default. Contact Progress Technical Support for further details if required. See article#  "LEAVE event not triggered for widgets consistently when embedding multiple ABL windows in a single .NET form" for details of the original issue.

References to other documentation:

Progress article(s):
 LEAVE event not triggered for widgets consistently when embedding multiple ABL windows in a single .NET form
 ROW-LEAVE trigger fires in Infinite loop when trying to focus widget in other frame, if trigger shows alert box and performs return no-apply