Automatically enable AdjustIndistinguishableColors if High Contrast mode enabled

[carlos-zamora]

Summary of the Pull Request

If High Contrast mode is enabled in the OS settings, we now automatically enable adjustIndistinguishableColors. To accomplish this, a new Automatic value is added to adjustIndistinguishableColors. When it's chosen, color nudging doesn't occur in regular contrast sessions, but we interpret the value as Indexed respectively.

The new default value is AutomaticIndexed. Meaning that regular contrast sessions will see no difference in behavior. However, if they switch to high contrast mode, Windows Terminal will interpret the value as Indexed at runtime. This was chosen because Always is more performance intensive.
  

References and Relevant Issues

#12999

Validation Steps Performed

✅ Toggling High Contrast mode immediately triggers an updated terminal instance with adjustIndistinguishableColors

[carlos-zamora]

For the record, AcessibilitySettings didn't work. Wasn't able to get the correct HighContrast value or be notified via HighContrastChanged. So I had to go the WM_SETTINGCHANGE route

https://learn.microsoft.com/en-us/uwp/api/windows.ui.viewmanagement.accessibilitysettings?view=winrt-22621

[lhecker]

1>D:\projects\terminal\src\renderer\atlas\AtlasEngine.r.cpp(493,19): error C2653: 'Feature_AtlasEnginePresentFallback': is not a class or namespace name

Hmm that's odd. Your PR doesn't touch anything like that. You may have to just do a good 'ol git clean -xfd and recompile from scratch, or maybe it's already sufficient to just build-clean the entire solution.

[DHowett]

I think @PankajBhojwani has some research on this with JTippet

[PankajBhojwani]

I wonder if we also want to increase the delta e threshold we use when we detect high contrast mode! That was what we discussed with Jeffrey Tippet (3 years ago at this point wow), his response was along the lines of "that makes sense, though know that this isn't the way win32 apps work". I think how color nudging should work with HC is something that likely needs more discussion/potentially a spec, but automatically turning on the feature when in HC mode makes sense as a start.

[carlos-zamora]

Ah, sounds like you're talking about this. 😏