[BUG] New or changed content not being conveyed to Assistive Technologies

[DaveTryon]

(This is split out from #1738)

From @delphinegilbert:

Hello,

An accessibility audit was performed on Accessibility Insights for Windows in our department and the following issue was found:

Description of issue

When shifting the separator bar left or right to reorganize the view using the keyboard, there is no feedback to assistive technologies that the action is successfully being performed.

Impact on users

This would have a limited impact on users; only sighted users would want to reorganize the view using this separator. Sighted users typically don't need assistive technologies to help them identify what's being done visually on the screen.

However, there are exceptions. For example, a sighted user with attention deficit might use a screen reader to help them keep their focus on what's going on on screen. In this scenario, such person might rely on screen reader feedback to let them know that they are changing the view - and how much (left / right) - in case they get distracted and are doing so none-intentionally.

That said, it would be fair to assume that the feature isn't a crucial one as it is mostly for esthetic. This issue isn't a show stopper.

Steps to reproduce

Launch Accessibility Insights, dismiss the opening dialog. You should see the main screen with the separator bar separating "Live Inspect" from the tab "Details". Using your keyboard, navigate to the separator bar and shift it's position left or right using the arrow keys.

[DaveTryon]

Note: We have 3 GridSplitter controls where this can come into play--they each have the id of gsMid are are located in the following 3 files:

• https://github.com/microsoft/accessibility-insights-windows/blob/main/src/AccessibilityInsights/Modes/EventModeControl.xaml
• https://github.com/microsoft/accessibility-insights-windows/blob/main/src/AccessibilityInsights/Modes/LiveModeControl.xaml
• https://github.com/microsoft/accessibility-insights-windows/blob/main/src/AccessibilityInsights/Modes/SnapshotModeControl.xaml

By default, the GridSplitter control supports the TransformPattern, but that doesn't expose any information about current location. A reasonable fix might be to create a custom version of GridSplitter that supports another pattern (maybe the ScrollPattern) to expose the horizontal position.

As has been previously pointed out, the ROI on this may not be enough to justify the effort.