Relayout open windows on terminal resize

NAWS mid-session updates now propagate to the window stack: Application
re-runs each open window's relayout on resize. Window#relayout re-centers
(clamped to the screen edge) by shifting all descendants; MasterDetail
recomputes its full geometry and re-renders the detail at the new width.
ButtonBar placement is extracted into ButtonBar.place for reuse.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/bbs/application.rb

@@ -236,6 +236,7 @@ module BBS
       @next      = FrameBuffer.new(c, r)
 
       relayout!
+      @windows.each { |w| w.relayout(self) } if resized
 
       @next.fill(x: 1, y: 1, width: c, height: r, sgr: @theme[:screen])
       @root.render(@next)

lib/bbs/window.rb

@@ -98,5 +98,24 @@ module BBS
     # Called once per Application idle tick (~1s). Override in subclasses that
     # need to poll for asynchronous updates (e.g. BBS::Windows::Stream).
     def tick(app); end
+
+    # Called by the Application when the terminal is resized. The default
+    # keeps the window's size and re-centers it, shifting every descendant
+    # along. Subclasses whose geometry depends on the terminal size override
+    # this (e.g. BBS::Windows::MasterDetail).
+    def relayout(app)
+      dx = [(app.cols - bounds.width) / 2 + 1, 1].max - bounds.x
+      dy = [(app.rows - bounds.height) / 2 + 1, 1].max - bounds.y
+      shift(dx, dy)
+    end
+
+    # Move the window and all its descendants by (dx, dy).
+    def shift(dx, dy)
+      return if dx.zero? && dy.zero?
+      walk do |w|
+        b = w.bounds
+        w.bounds = Widget::Rect.new(b.x + dx, b.y + dy, b.width, b.height)
+      end
+    end
   end
 end

lib/bbs/windows/button_bar.rb

@@ -32,6 +32,24 @@ module BBS
           BBS::Widgets::Button.new(label: d[:label], on_click: build_handler(window, app, d))
         end
 
+        place(window, widgets, descriptors)
+
+        widgets.each { |w| window.add(w) }
+
+        primary_idx = descriptors.index { |d| d[:primary] }
+        primary     = primary_idx ? widgets[primary_idx] : nil
+
+        by_key = {}
+        descriptors.each_with_index { |d, i| by_key[d[:key]] = widgets[i] if d[:key] }
+
+        { widgets: widgets, primary: primary, by_key: by_key }
+      end
+
+      # Position (or re-position) already-built bar widgets against the
+      # window's current bounds. Used by attach and by window relayouts.
+      def place(window, widgets, descriptors)
+        return if widgets.empty?
+
         default_align = descriptors.length == 1 ? :center : :right
         aligns        = descriptors.map { |d| d[:align] || default_align }
 
@@ -68,16 +86,6 @@ module BBS
           widgets[i].layout(x, row_y, bw, 1)
           x += bw + 1
         end
-
-        widgets.each { |w| window.add(w) }
-
-        primary_idx = descriptors.index { |d| d[:primary] }
-        primary     = primary_idx ? widgets[primary_idx] : nil
-
-        by_key = {}
-        descriptors.each_with_index { |d, i| by_key[d[:key]] = widgets[i] if d[:key] }
-
-        { widgets: widgets, primary: primary, by_key: by_key }
       end
 
       def button_width(button)

lib/bbs/windows/master_detail.rb

@@ -81,47 +81,68 @@ module BBS
         end
       end
 
+      # Terminal resized: recompute the whole geometry against the new size
+      # and re-render the detail at the new pane width.
+      def relayout(_app = @app)
+        place_window
+        place_panes
+        ButtonBar.place(self, @bar[:widgets], @actions)
+        reload_detail
+      end
+
       private
 
       def build
-        w = @width  || @app.cols - 4
+        place_window
-        h = @height || @app.rows - 6
-        x = (@app.cols - w) / 2 + 1
-        y = (@app.rows - h) / 2 + 1
-        layout(x, y, w, h)
-
-        has_buttons = !@actions.empty?
-        has_meta    = !@bottom_meta.nil?
-        panel_h     = h - 4 - (has_meta ? 1 : 0) - (has_buttons ? 1 : 0)
-        panel_h     = [panel_h, 3].max
-
-        list_w = @list_width || [(w / 3).clamp(20, 40), w - 10].min
-        list_x = bounds.x + 2
-        list_y = bounds.y + 2
 
         @list_widget = BBS::Widgets::ListBox.new(
           items: @items,
-          label: ->(item) { "  #{@item_label.call(item)}".ljust(list_w) }
+          label: ->(item) { "  #{@item_label.call(item)}".ljust(@list_w || 0) }
         )
-        @list_widget.layout(list_x, list_y, list_w, panel_h)
         add(@list_widget)
 
-        detail_x = list_x + list_w + 2
-        detail_w = bounds.width - list_w - 5
         @detail_view = BBS::Widgets::ScrollView.new(lines: [])
-        @detail_view.layout(detail_x, list_y, detail_w, panel_h)
         add(@detail_view)
 
-        if has_meta
+        unless @bottom_meta.nil?
-          meta_y = bounds.y + h - (has_buttons ? 3 : 2)
           @meta_label = BBS::Widgets::Label.new(text: '', style_key: :input_label)
-          @meta_label.layout(bounds.x + 2, meta_y, bounds.width - 4, 1)
           add(@meta_label)
         end
 
         @list_widget.on_select = ->(_, _) { reload_detail }
 
-        ButtonBar.attach(self, @app, @actions)
+        @bar = ButtonBar.attach(self, @app, @actions)
+        place_panes
+      end
+
+      def place_window
+        w = @width  || @app.cols - 4
+        h = @height || @app.rows - 6
+        x = (@app.cols - w) / 2 + 1
+        y = (@app.rows - h) / 2 + 1
+        layout(x, y, w, h)
+      end
+
+      def place_panes
+        h           = bounds.height
+        has_buttons = !@actions.empty?
+        has_meta    = !@meta_label.nil?
+        panel_h     = h - 4 - (has_meta ? 1 : 0) - (has_buttons ? 1 : 0)
+        panel_h     = [panel_h, 3].max
+
+        @list_w = @list_width || [(bounds.width / 3).clamp(20, 40), bounds.width - 10].min
+        list_x  = bounds.x + 2
+        list_y  = bounds.y + 2
+        @list_widget.layout(list_x, list_y, @list_w, panel_h)
+
+        detail_x = list_x + @list_w + 2
+        detail_w = bounds.width - @list_w - 5
+        @detail_view.layout(detail_x, list_y, detail_w, panel_h)
+
+        if @meta_label
+          meta_y = bounds.y + h - (has_buttons ? 3 : 2)
+          @meta_label.layout(bounds.x + 2, meta_y, bounds.width - 4, 1)
+        end
       end
     end
   end