Description

Pasting a button element from one Widget Blueprint into a second Widget Blueprint that has had its root Canvas Panel deleted results in a crash. The crash only occurs when the Canvas Panel is deleted. It also did not occur when I tested it with a Progress Bar and a Text Box, so it may be behavior specific to the button widget.

Tested in //UE4/Release-4.25 @ CL 14469661 and this did NOT occur, so marking as a Regression

Steps to Reproduce
  1. Create a Widget Blueprint
  2. Add a button from the palette
  3. Copy the button
  4. Create another Widget Blueprint
  5. Delete the Canvas Panel in the 2nd WBP
  6. Paste the button from the 1st WBP into the second WBP

RESULT:

The engine crashes

EXPECTED:

The button is pasted into the second WBP

Callstack
=== Critical error: ===

Fatal error!

Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x0000000000000010

[Callstack] 0x00007ff880881911 UE4Editor-UMGEditor.dll!FWidgetBlueprintEditorUtils::PasteWidgetsInternal() [D:\Build\++UE4\Sync\Engine\Source\Editor\UMGEditor\Private\WidgetBlueprintEditorUtils.cpp:1337]
[Callstack] 0x00007ff88088143e UE4Editor-UMGEditor.dll!FWidgetBlueprintEditorUtils::PasteWidgets() [D:\Build\++UE4\Sync\Engine\Source\Editor\UMGEditor\Private\WidgetBlueprintEditorUtils.cpp:1318]
[Callstack] 0x00007ff880881026 UE4Editor-UMGEditor.dll!FWidgetBlueprintEditor::PasteWidgets() [D:\Build\++UE4\Sync\Engine\Source\Editor\UMGEditor\Private\WidgetBlueprintEditor.cpp:526]
[Callstack] 0x00007ff8808384d6 UE4Editor-UMGEditor.dll!TBaseSPMethodDelegateInstance<0,FWidgetBlueprintEditor,0,void __cdecl(void),FDefaultDelegateUserPolicy>::ExecuteIfSafe() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Core\Public\Delegates\DelegateInstancesImpl.h:307]
[Callstack] 0x00007ff8d20b33a9 UE4Editor-Slate.dll!FUICommandList::ConditionalProcessCommandBindings() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\Commands\UICommandList.cpp:220]
[Callstack] 0x00007ff8d20ec62a UE4Editor-Slate.dll!FUICommandList::ProcessCommandBindings() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\Commands\UICommandList.cpp:164]
[Callstack] 0x00007ff880798f94 UE4Editor-UMGEditor.dll!SDesignerView::OnKeyDown() [D:\Build\++UE4\Sync\Engine\Source\Editor\UMGEditor\Private\Designer\SDesignerView.cpp:2005]
[Callstack] 0x00007ff8d20825b2 UE4Editor-Slate.dll!FEventRouter::Route<FReply,FEventRouter::FBubblePolicy,FKeyEvent,<lambda_f630e7f24dbef73857a69219e32f2d96> >() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:383]
[Callstack] 0x00007ff8d20ee368 UE4Editor-Slate.dll!FSlateApplication::ProcessKeyDownEvent() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:4325]
[Callstack] 0x00007ff8d20e2226 UE4Editor-Slate.dll!FSlateApplication::OnKeyDown() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:4222]
[Callstack] 0x00007ff8e92db958 UE4Editor-ApplicationCore.dll!FWindowsApplication::ProcessDeferredMessage() [D:\Build\++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:2013]
[Callstack] 0x00007ff8e92c9197 UE4Editor-ApplicationCore.dll!FWindowsApplication::DeferMessage() [D:\Build\++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:2642]
[Callstack] 0x00007ff8e92de389 UE4Editor-ApplicationCore.dll!FWindowsApplication::ProcessMessage() [D:\Build\++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:1046]
[Callstack] 0x00007ff8e92c4310 UE4Editor-ApplicationCore.dll!FWindowsApplication::AppWndProc() [D:\Build\++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:878]
[Callstack] 0x00007ff9059f5c1d USER32.dll!UnknownFunction []
[Callstack] 0x00007ff9059f5612 USER32.dll!UnknownFunction []
[Callstack] 0x00007ff8e92df914 UE4Editor-ApplicationCore.dll!FWindowsPlatformApplicationMisc::PumpMessages() [D:\Build\++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsPlatformApplicationMisc.cpp:130]
[Callstack] 0x00007ff70f9e8848 UE4Editor.exe!FEngineLoop::Tick() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:4748]
[Callstack] 0x00007ff70fa0117c UE4Editor.exe!GuardedMain() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:169]
[Callstack] 0x00007ff70fa0125a UE4Editor.exe!GuardedMainWrapper() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:137]
[Callstack] 0x00007ff70fa152bd UE4Editor.exe!WinMain() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:268]
[Callstack] 0x00007ff70fa17fea UE4Editor.exe!__scrt_common_main_seh() [d:\agent\_work\5\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
[Callstack] 0x00007ff9068f7c24 KERNEL32.DLL!UnknownFunction []
[Callstack] 0x00007ff90758d721 ntdll.dll!UnknownFunction []

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Fixed
ComponentTools - UMG
Affects Versions4.26.2
Target Fix4.27
Fix Commit16160497
Main Commit16161176
Release Commit16160497
CreatedApr 13, 2021
ResolvedApr 29, 2021
UpdatedMay 8, 2021
Pull Requests
7948 - mrbindraw