new framework

lib/bbs/widget.rb

@@ -0,0 +1,82 @@
+# frozen_string_literal: true
+
+module BBS
+  # Base widget. All visual elements inherit from this.
+  #
+  #   bounds — Rect (x, y, width, height) in screen coordinates
+  #   parent — enclosing Container, or nil
+  #   id     — optional symbol for lookup via Container#find
+  #
+  # Subclasses override render(frame) and optionally handle_event(event).
+  class Widget
+    Rect = Struct.new(:x, :y, :width, :height) do
+      def contains?(px, py)
+        px >= x && px < x + width && py >= y && py < y + height
+      end
+
+      def to_s = "##{x},#{y} #{width}x#{height}"
+    end
+
+    attr_accessor :bounds, :parent, :id, :visible, :focused, :enabled
+    attr_reader   :theme
+
+    def initialize(id: nil, bounds: nil, theme: nil)
+      @id       = id
+      @bounds   = bounds || Rect.new(1, 1, 0, 0)
+      @parent   = nil
+      @visible  = true
+      @focused  = false
+      @enabled  = true
+      @theme    = theme
+    end
+
+    # Override in subclasses. By default a widget does not accept focus.
+    def focusable? = false
+
+    # Called when this widget gains focus. Subclasses may override.
+    def on_focus = nil
+
+    # Called when this widget loses focus.
+    def on_blur = nil
+
+    # Render this widget into the supplied FrameBuffer.
+    def render(frame); end
+
+    # Handle a keyboard or mouse event. Return :halt to end the application,
+    # :handled to stop propagation, or nil/false to continue.
+    def handle_event(_event) = nil
+
+    # Convenience: yield this widget. Subclasses override to walk a tree.
+    def each(&block)
+      yield self
+      nil
+    end
+
+    # Hit test: returns the deepest widget whose bounds contain (x, y).
+    def hit_test(x, y)
+      bounds.contains?(x, y) ? self : nil
+    end
+
+    # Apply a theme. Subclasses with children propagate via Container#theme=.
+    def theme=(value)
+      @theme = value
+    end
+
+    # Move/resize. Subclasses may override to relayout children.
+    def layout(x, y, width, height)
+      @bounds = Rect.new(x, y, width, height)
+    end
+
+    # Request a redraw — set by Application as a callback if needed.
+    def redraw!
+      @parent&.redraw!
+    end
+
+    protected
+
+    def style(key)
+      th = @theme || (parent && parent.theme)
+      th ? th.style(key) : nil
+    end
+  end
+end