[CrashReport] FSlateRHIRenderer::ConditionalResizeViewport()

This is a common crash occurring on Windows and Mac in 4.15 and 4.16 (two different callstacks with close similarities). The callstack is also similar to [Link Removed] and may be related.

User Descriptions

• seems the issues is going out of vr preview window and then it crashes
• tried to open the 2d strategy pack downloaded - first time running
• I opened the game level in the VR preview. I exited out of it to return to the editor. After about 2 secs, it crashed.
• This is a crash that has been happening on a frequent basis in 4.18.1 (and also 4.18.2 update). I have tried several ideas to isolate the bug :- - Deleting blueprints / objects creating an empty scene - Resetting default game mode - Fresh 4.18.2 project with stock only assets. While my older project still crashes quite consistently when I enter play mode, exit play mode and try to edit objects in windows, it doesn’t always crash like this. it's mostly when I enter play and exit to continue to work on my project, but one occasion it did crash when I never once entered play mode. Previously I could 'safely' work on my project in Simulate mode, without any crash issues but this whole bug is very inconsistent and hard to pin down. My new stock project did crash once when I entered play mode, exited play mode and opened up the projects menu. But I cannot seem to recreate this bug in the new project. Again, inconsistent and incredibly hard to pin down.

repro steps currently unknown

Fatal error: [Link Removed] [Line: 327] SwapChain->ResizeBuffers(1,SizeX,SizeY,RenderTargetFormat,DXGI_SWAP_CHAIN_FLAG_ALLOW_MODE_SWITCH) failed at D:\Build++UE4+Release-4.16+Compile\Sync\Engine\Source\Runtime\Windows\D3D11RHI\Private\D3D11Viewport.cpp:220 with error DXGI_ERROR_INVALID_CALL, Size=536x256 Format=DXGI_FORMAT_R10G10B10A2_UNORM(0x00000018)

UE4Editor_D3D11RHI!VerifyD3D11ResizeViewportResult() [d3d11util.cpp:318]
UE4Editor_D3D11RHI!FD3D11Viewport::Resize() [d3d11viewport.cpp:222]
UE4Editor_SlateRHIRenderer!FSlateRHIRenderer::ConditionalResizeViewport() [slaterhirenderer.cpp:405]
UE4Editor_SlateRHIRenderer!FSlateRHIRenderer::DrawWindows_Private() [slaterhirenderer.cpp:1031]
UE4Editor_Slate!FSlateApplication::PrivateDrawWindows() [slateapplication.cpp:1453]
UE4Editor_Slate!FSlateApplication::DrawWindows() [slateapplication.cpp:1149]
UE4Editor_Slate!FSlateApplication::TickApplication() [slateapplication.cpp:1726]
UE4Editor_Slate!FSlateApplication::Tick() [slateapplication.cpp:1548]
UE4Editor!FEngineLoop::Tick() [launchengineloop.cpp:3182]
UE4Editor!GuardedMain() [launch.cpp:166]
UE4Editor!GuardedMainWrapper() [launchwindows.cpp:134]
UE4Editor!WinMain() [launchwindows.cpp:210]
UE4Editor!__scrt_common_main_seh() [exe_common.inl:253]
kernel32!BaseThreadInitThunk()
ntdll!RtlUserThreadStart()