highlightMode property Null safety
Indicates the current interaction mode for focus highlights.
The value returned depends upon the highlightStrategy used, and possibly (depending on the value of highlightStrategy) the most recent interaction mode that they user used.
If highlightMode returns FocusHighlightMode.touch, then widgets should not draw their focus highlight unless they perform text entry.
If highlightMode returns FocusHighlightMode.traditional, then widgets should draw their focus highlight whenever they are focused.
Implementation
// Don't want to set _highlightMode here, since it's possible for the target
// platform to change (especially in tests).
FocusHighlightMode get highlightMode => _highlightMode ?? _defaultModeForPlatform;