Fixed narrator not announcing RangeSelector values / changes

[Arlodotexe]

Overview

Bugfix, Fixes #3538

Current behavior

Narrator does not announce range selector values or updates to the values.

New behavior

Narrator now announces range selector values and updates.

To do this, I've

• Added a new RangeThumb control - derives from RangeBase.
  • Binds min/max/value to the range selector.
  • Wraps around a Windows.UI.Xaml.Controls.Primitives.Thumb control, using the existing style.
  • Relays the needed events from the wrapped Thumb for range selector to use.
• Added a new RangeThumbAutomationPeer class - takes in a RangeThumb and is treated like a slider.
• Swapped Thumb with RangeThumb - in RangeSelector, RangeThumb has been implemented and fully integrated.
• Tested the new behavior -- to make sure Narrator now works as expected.

Short demo of the new behavior:

recordedVideo2021-12-29-140436.mp4

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• New component
  • Pull Request has been submitted to the documentation repository instructions. Link:
  • Added description of major feature to project description for NuGet package (4000 total character limit, so don't push entire description over that)
  • If control, added to Visual Studio Design project
• Sample in sample app has been added / updated (for bug fixes / features)
  • Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• New major technical changes in the toolkit have or will be added to the Wiki e.g. build changes, source generators, testing infrastructure, sample creation changes, etc...
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Header has been added to all new source files (run build/UpdateHeaders.bat)
• Contains NO breaking changes

[ghost]

Thanks Arlodotexe for opening a Pull Request! The reviewers will test the PR and highlight if there is any conflict or changes required. If the PR is approved we will proceed to merge the pull request 🙌

[michael-hawker]

Rather than creating an entirely new sub-class of Thumb just for an automation peer, can we not create a RangeSelectorAutomationPeer and raise events when the thumb properties change to alert the automation clients that it's changed?

Love the result from the video, but just wondering if we can simplify this to make it more maintainable and not expose a new class that we wouldn't want folks to pick-up and use. @chingucoding any suggestions? Or am I missing something about what's possible with an automation peer? Like wondering if we can use sub-peers to get the name of the thumb changing if need be or something? https://docs.microsoft.com/en-us/windows/apps/design/accessibility/custom-automation-peers#:~:text=Forwarding%20patterns%20from%20sub%2Delements

[Arlodotexe]

@michael-hawker That's really helpful, I wasn't aware of this option! If this works it'll be a better option, it avoids creating a new control and potentially breaking custom styles that devs have already made in their app.

I'll wait a bit for notes from @chingucoding before digging into this more.

[marcelwgn]

Rather than creating an entirely new sub-class of Thumb just for an automation peer, can we not create a RangeSelectorAutomationPeer and raise events when the thumb properties change to alert the automation clients that it's changed?

I think this could be a fairly good approach to this. I think we wouldn't really support any patterns since the all don't seem to fit really well here and we would should use the control type custom.

Love the result from the video, but just wondering if we can simplify this to make it more maintainable and not expose a new class that we wouldn't want folks to pick-up and use. @chingucoding any suggestions? Or am I missing something about what's possible with an automation peer? Like wondering if we can use sub-peers to get the name of the thumb changing if need be or something? https://docs.microsoft.com/en-us/windows/apps/design/accessibility/custom-automation-peers#:~:text=Forwarding%20patterns%20from%20sub%2Delements

I think you are slightly misunderstanding the pattern forwarding. In our case, we would want to get the name of the thumbs. If i understand the pattern forwarding correctly, you would use for example if assistive technology asks your control if it supports the scroll pattern and ListView for example would then return the internal scroll viewer. Getting the names of the thumbs should be fairly easy by just getting their automation peer and getting their AutomationProperties.Name property. Though I'm inclined to say that the "Minimum" or "Maximum" value changed instead of "Minimum value thumb" or what ever the UIA name of the thumb could be.

[michael-hawker]

@Arlodotexe @niels9001 did this carry forward to the new control or did it get fixed with the other improvements made?

If fixed, let's close this PR and the corresponding bug (pointing to the new repo/release), otherwise, we can transfer the bug forward to the new repo.