View — Focus

Keyboard focus determines which view receives OnKeyDown and OnChar events. Focus is managed through the IFocus service, which is resolved via the parent chain and provided by RootView.

Participating in focus

public virtual bool Focusable => false;

Override and return true to opt in to Tab navigation. Only focusable views are visited during IFocus.Next() / IFocus.Previous().

Querying and changing focus

public bool IsFocused { get; }   // true if this view holds focus
public bool Focus()              // request focus; returns false if no IFocus service
public void Blur()               // release focus from this view

All three resolve IFocus via this.GetService<IFocus>() (see DI). If the view is not in a tree rooted at a RootView, the service will be null and Focus() returns false.

Focus notifications

protected internal virtual void OnFocus() { }
protected internal virtual void OnBlur()  { }

These are called by RootView when IFocus.FocusedView changes. Override to react to focus changes — for example to start a caret blink animation in OnFocus and stop it in OnBlur.

IFocus service

RootView implements IFocus and registers itself via GetService:

View? FocusedView { get; set; }  // get/set the focused view directly
void Next()                      // move to the next focusable (Tab)
void Previous()                  // move to the previous focusable (Shift+Tab)

Tab navigation performs a depth-first walk of the tree, collecting all Focusable views in order.