Winforms: [Accessibility] ComboBox control causes Narrator and Inspect to stop responding

[Jessie-Zhang01]

• .NET Core Version:
  .Net 5.0.100-preview.7.20314.1 from 5.0 master branch

• Have you experienced this same bug with .NET Framework?:
  No

More Info:

1. This issue can also reproduce on without Private.
2. This issue can reproduce in RTL and LTR environment.

Minimal repro:

1. Open the attached ‘WindowsFormsApp3’ application in VS, then build and run it.
2. Open Narrator or Inspect, then focus it's cursor to the ComboBox control.
   WindowsFormsApp4.zip

Expected behavior:
Narrator or Inspect's cursor focuses on the ComboBox control and works fine.

Actual behavior:
ComboBox control causes Narrator and Inspect not respond.

[merriemcgaw]

@Jessie-Zhang01 is this a regression? Can you double check if this is a regression from a previous Preview?

[Jessie-Zhang01]

@merriemcgaw yes, this is a regression issue. It's can reproduce on .Net 5.0.100-preview.5.20270.37, but cannot reproduce on .Net 5.0.100-preview.4.20258.7.

[Tanya-Solyanik]

@vladimir-krestov - could you please take a look at the ComboBox page from our test application, when expanding ComboBox drop downs and selecting items under inspect, inspect eventually hangs.

[Jessie-Zhang01]

Verified this issue with .Net 5.0.100-preview.8.20362.3 from Master branch, this issue is fixed. Narrator or Inspect's cursor focuses on the ComboBox control and works fine. Please see following gif.

[Tanya-Solyanik]

@Jessie-Zhang01 - could you please try the WinformsControlsTest application that is included into our integration tests.

[Jessie-Zhang01]

@Tanya-Solyanik I tested the WinformsControlsTest application and found a issue: when the "ComboBox" to be expanded contains the same item(set DropDownStyle property of ComboBox as 'DropDown/DropDownList'), Narrator/Inspect eventually hang. Please see following gif:

In addition, this issue cannot reproduce when set DropDownStyle property of ComboBox as 'Simple'.

[merriemcgaw]

@Jessie-Zhang01 Does this impact 3.1?

[Jessie-Zhang01]

@merriemcgaw yes, this issue also can reproduce on .Net Core 3.1.

[merriemcgaw]

@RussKie @vladimir-krestov - we need to consider this for servicing in 3.1 as well as the 5.0 fix.

[Tanya-Solyanik]

@Jessie-Zhang01 - Wow, nice job finding a min repro! I think a new more specific issue should be opened. Could you please create a new one with your repro app and close this one.

Could you please double-check if this is broken in NETFX 4.8 and open a bug in AzDo if it is?

It's still not clear why the removal of ComImport attribute fixes this hang though.

[Jessie-Zhang01]

@Tanya-Solyanik I filed a new GitHub issue 3590 for it, so close the current issue. And this issue can also reproduce on .Net 4.8, so create a new VSO bug: 1157357.

[AaronRobinsonMSFT]

@RussKie @JeremyKuhne @vladimir-krestov I do not believe that https://github.com/dotnet/winforms/pull/3524 was an appropriate fix here. Based on my investigation the removal of ComImport has simply disabled support for IRawElementProviderHwndOverride. This then "works" because the interface is not used. It appears that the specific scenario used for validation works, but it is hiding some underlying condition. I have stepped through the UI Accessibility layer and verified that the call to IRawElementProviderHwndOverride.GetOverrideProviderForHwnd() is succeeding without error from the native side of things. I also verified the managed function tends to work so it is a consequence of the return value or perhaps a misunderstanding of the Accessibility API. I am not sure and admit I have no knowledge of how it should be used, but do know that .NET is properly projecting the interface when ComImport is attributed which is correct as @weltkante has pointed out here.

Given the statement in https://github.com/dotnet/winforms/issues/3590 about .NET 4.8, it is entirely possible that the type was never properly respected and this has been a long standing bug that was recently found now that it is properly defined with ComImport.

[merriemcgaw]

@Tanya-Solyanik, can you chat with @AaronRobinsonMSFT for a high level overview of AccessibleObject?

[merriemcgaw]

It's looking like it might be close to get it in 5.0 Adding @JeremyKuhne

[merriemcgaw]

@JeremyKuhne what are your thoughts about 5.0GA

[RussKie]

Is this still an issue in RC2?

[Jessie-Zhang01]

@RussKie Verified this issue with .Net 5.0.100-rc.2.20466.4, when the "ComboBox" to be expanded contains the different item, Narrator or Inspect's cursor focuses on the ComboBox control and works fine.
But when the "ComboBox" to be expanded contains the same item, Narrator/Inspect eventually hang(have a known issue: 3590).

[merriemcgaw]

@Jessie-Zhang01 does it take a while for the hang to happen when we've got the duplicate items in the ComboBox?

[Jessie-Zhang01]

@merriemcgaw No, The Accessibility tools: Narrator/Inspect/Accessibility Insight and test project all are hung when using them together until clicking the stop button in VS toolbar when expand the ComboBox drop-down list with the duplicate items. Please see following gif:

[RussKie]

@merriemcgaw do we want to service this?

[merriemcgaw]

Yes, I think we do.