class BBS::FocusManager

Tracks which widget within a Container currently has focus. Tab / Shift-Tab cycle through its focusable descendants.

Constants

FOCUS_KEYS: The focus moves of Tab and Shift-Tab.

Attributes

focused [R]

The widget that has the focus, or nil.

Public Class Methods

new (container)

Source

# File lib/bbs/focus_manager.rb, line 12
def initialize(container)
  @container = container
  @focused   = nil
  focus_first
end

Creates a manager for container, a BBS::Container, and focuses its first candidate.

Public Instance Methods

candidates ()

Source

# File lib/bbs/focus_manager.rb, line 20
def candidates
  @container.focusable_descendants.select(&:enabled)
end

Returns the widgets that can take the focus: the container’s visible, focusable and enabled descendants, in walk order.

dispatch (event)

Source

# File lib/bbs/focus_manager.rb, line 59
def dispatch(event)
  return nil unless @focused
  @focused.handle_event(event)
end

Passes event to the focused widget’s handle_event.

Returns the widget’s result, or nil when nothing has the focus.

focus (widget)

Source

# File lib/bbs/focus_manager.rb, line 32
def focus(widget)
  move_focus(widget) if widget&.focusable? && widget.enabled
end

Moves the focus to widget when it is focusable and enabled; otherwise leaves the focus where it is. The old widget gets on_blur, the new one on_focus.

focus_first ()

Source

# File lib/bbs/focus_manager.rb, line 25
def focus_first
  move_focus(candidates.first)
end

Moves the focus to the first candidate, or clears it when there is none.

handle_focus_key (event)

Source

# File lib/bbs/focus_manager.rb, line 48
def handle_focus_key(event)
  move = event.key? && FOCUS_KEYS[event.key]
  return nil unless move

  public_send(move)
  :handled
end

Handles Tab (next) and Shift-Tab (previous) in event, a BBS::Event.

Returns :handled when the key moved the focus, nil otherwise.

next_focus ()

Source

# File lib/bbs/focus_manager.rb, line 37
def next_focus = step_focus(1, -1)

Moves the focus to the next candidate, wrapping around at the end.

prev_focus ()

Source

# File lib/bbs/focus_manager.rb, line 40
def prev_focus = step_focus(-1, 0)

Moves the focus to the previous candidate, wrapping around at the start.