Added Container#clear to remove child elements and optionally eval block, improvements to EditLine to show current selection.

lib/cyberarm_engine/ui/elements/container.rb

@@ -2,6 +2,7 @@ module CyberarmEngine
   class Element
     class Container < Element
       include Common
+      include CyberarmEngine::DSL
 
       attr_accessor :stroke_color, :fill_color
       attr_reader :children, :gui_state
@@ -31,6 +32,12 @@ module CyberarmEngine
         recalculate
       end
 
+      def clear(&block)
+        @children.clear
+
+        block.call(self) if block
+      end
+
       def render
         Gosu.clip_to(@x, @y, width, height) do
           @children.each(&:draw)