bug(windows): backspace with selected text deletes an extra character in TSF only

[mcdurdin]

Describe the bug

Per Jeff Heath at https://community.software.sil.org/t/ios-and-android-undesirable-behaviour-with-selected-text/6986/2:

... unexpected behavior on Windows 11 (but I believe also on Windows 10 as well) when I have some text selected and I press backspace. It deletes the selected text, but also the previous character.

...

I can demonstrate the behavior right now in Word 2019. With my keyboard activated, type “A test”, select “test” and type backspace, and the space is deleted as well. It doesn’t do this in LibreOffice Writer.

I have seen this behavior for quite some time, maybe a year, but I don’t remember it happening before that. So I think it must have happened with some Keyman version change.

This looks like a regression, perhaps in Keyman 15? We should track down the exact release where this behaviour changed.

Reproduce the bug

No response

Expected behavior

No response

Related issues

• bug(iOS): selecting text and then backspacing also deletes the character before the selection #7865
• bug(web): pressing layer switch key with selected text would delete the selection #7866

Keyman apps

• Keyman for Android
• Keyman for iPhone and iPad
• Keyman for Linux
• Keyman for macOS
• Keyman for Windows
• Keyman Developer
• KeymanWeb
• Other - give details at bottom of form

Keyman version

15.0.274

Operating system

Windows 11

Device

No response

Target application

No response

Browser

No response

Keyboard name

No response

Keyboard version

No response

Language name

No response

Additional context

No response

[mcdurdin]

• Keyman 16.0.119-beta: Tested and replicated, with both Keyman Core on and off.
• Keyman 14.0.286: Tested and replicated.
• Keyman 10.0.1208.0: Tested and replicated.

So this is not a new issue, it is long-standing. However I can reliably replicate it.

[rc-swag]

These are just some notes I have as much for myself to investigate further.
As noted a long-standing issue with the TSF.
To Investigate

• How is Keyman is using the TSF (interface) to interact with select text (if at all) Verses how the TSF applications expect it to act with selected text and backspace. For example I can see there is a SetText range command.
• ITfContextKeyEventSink vs ITfKeyEventSink

I noticed select text and pressing delete, just deletes the text select and select text and pressing a character key causes the replication of the selected text.

[rc-swag]

Further information from a new community site post points out the direction of the selection determines which extra character is deleted.

When I select a text in Microsoft Word, BACKSPACE deletes selected texts + an extra character (the previous or following one, depending on what direction I selected the text.

@Nnyny has also created steps to reproduce.

I was investigate on a community site post and able to reproduce a similar behavior on my computer. Whether I selected from left or right, it will delete the extra character(or a space) at the left.

Reproduce the bug

1. Open MS Word
2. Type 'mySchool'
3. Select 'School' and click backspace to delete it
4. Show only the letter 'm'

Expected behavior

'School' got deleted and we get 'my'

Related issues

No response

Keyman apps

• Keyman for Windows

Keyman version

17.0.326

Operating system

Windows 11 Home Single Language 22H2

Target application

Microsoft Word 2019

Keyboard name

US Basic

[rc-swag]

With logging today I can see an issue with how the Windows engine is interacting with the core. The windows is setting the context in the core km_core_state_context_set_if_needed with the context preceding the selected text. The core then returns the text do delete to be the last letter of that context which is the text before the selected text. I further inestigation to complete to see how the windows engine should be interacting with the application. Just recording this info here.

[Nnyny]

moved to new issue #11893
More information from the post:

Hello! I’d like to report another bug, hoping this is useful. It’s a similar issue: when selecting a text and there’s no character to delete, the text formating is deleted instead.

For example, if a text is bold and in italics, and I double click on it to overwrite it with new text, it comes out as regular (again, if there’s no extra character to delete, e.g. at the beginning of a paragraph.