Implement client visibility state

lib/uh/wm/client.rb

@@ -7,12 +7,21 @@ module Uh
       def initialize window, geo = nil
         @window   = window
         @geo      = geo
+        @visible  = false
       end
 
       def to_s
         "<#{name}> (#{wclass}) #{@geo} win: #{@window}"
       end
 
+      def visible?
+        @visible
+      end
+
+      def hidden?
+        not visible?
+      end
+
       def name
         @wname ||= @window.name
       end

spec/uh/wm/client_spec.rb

@@ -8,6 +8,14 @@ module Uh
       end
       subject(:client)  { described_class.new window, geo }
 
+      it 'is not visible' do
+        expect(client).not_to be_visible
+      end
+
+      it 'is hidden' do
+        expect(client).to be_hidden
+      end
+
       describe '#to_s' do
         it 'includes window name' do
           expect(client.to_s).to include 'wname'