NRE In Unmanaged Code When Pressing Keys In TreeView about winforms

[stumper66]

@elachlan I will submit a PR.
I've been unable to provide a test but I fixed the problem with my own locallly built System.Windows.Forms.dll with the submitted fork: stumper66@ae5cd93

[Olina-Zhang]

It is a similar with GH issue: #7262 with same CallStack, but we cannot reproduce for our created application. Hopefully a repro application provided.

[stumper66]

Full callstack:
System.NullReferenceException
HResult=0x80004003
Message=Object reference not set to an instance of an object.
Source=System.Windows.Forms
StackTrace:
at System.Windows.Forms.Control.GetSafeHandle(IWin32Window window)
at System.Windows.Forms.ToolTip.TryGetBubbleSize(IKeyboardToolTip tool, Size& bubbleSize)
at System.Windows.Forms.ToolTip.ShowKeyboardToolTip(String text, IKeyboardToolTip tool, Int32 duration)
at System.Windows.Forms.KeyboardToolTipStateMachine.ShowToolTip(IKeyboardToolTip tool, ToolTip toolTip)
at System.Windows.Forms.KeyboardToolTipStateMachine.Transition(IKeyboardToolTip tool, ToolTip tooltip, SmEvent event)
at System.Windows.Forms.KeyboardToolTipStateMachine.Transit(SmEvent event, IKeyboardToolTip source)
at System.Windows.Forms.Timer.TimerNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(HWND hWnd, MessageId msg, WPARAM wparam, LPARAM lparam)
at Windows.Win32.PInvoke.DispatchMessage(MSG* lpMsg)
at System.Windows.Forms.Application.ComponentManager.Microsoft.Office.IMsoComponentManager.FPushMessageLoop(UIntPtr dwComponentID, msoloop uReason, Void* pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(msoloop reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(msoloop reason, ApplicationContext context)
at ManageVMs_Core.Program.Main() in C:\Users\buffalo\Documents\Visual Studio 2022\Projects\ManageVMs_Core\ManageVMs_Core\Program.cs:line 29

This exception was originally thrown at this call stack:
[External Code]
ManageVMs_Core.Program.Main() in Program.cs

[stumper66]

Here is my fix for it: stumper66@ae5cd93

[elachlan]

@stumper66 did you want to submit a PR and provide a test?

@Olina-Zhang Is your team able to reproduce this issue in the test project?

[stumper66]

@elachlan Here is the PR: #11092

[elachlan]

I think it might be prudent to investigate what kind of tooltip its trying to show and what triggers it?

[stumper66]

I do not have any tool tips defined.
I had added debugging inside the function, here is one of the values I logged as I was pressing on the keys.

03/19/2024 17:14:50.838  inside TryGetBubbleSize, tool: DataGridViewTextBoxCell { ColumnIndex=0, RowIndex=-1 }

Note that I have the TreeView updating a DataGridView based on its values so looks like it's coming from there.

[elachlan]

@stumper66 could you debug the WinformsControlsTest project and try to reproduce it there? Maybe set a breakpoint and look at the call stack to see what causes the tooltip to be triggered?

[stumper66]

There is possibly a trigger for the toolip that shouldn't be there but if you look at my PR it's making a change that should've been there to begin with. It's getting passed a nullable value then assuming it is not null.
By checking if it's not null first it fails the ghost tooltip gracefully.

Since the tooltip is not triggered by any user code it is very hard to pin down. I've been dealing with this bug for years hoping each new .net version would fix it.

[merriemcgaw]

Can we change this PR to .NET 9 main, and we will need to be the ones to cherry-pick it ourselves to take it in servicing. @Tanya-Solyanik to drive this through shiproom and follow the fix.

[stumper66]

I've created a new PR targetting main branch.
#11134