added image widget with atlas support and global texture manager

engine/layout.cpp

@@ -3,6 +3,8 @@
 #include "util.h"
 
 Plane WidgetBorder::m_plane;
+Plane WidgetImage::m_plane;
+Sampler WidgetImage::m_sampler;
 
 void Node::update(float width, float height)
 {
@@ -221,6 +223,9 @@ void Node::load_internal(const tinyxml2::XMLElement* x_node)
     case kWidget::Text:
         m_widget = std::make_unique<WidgetText>();
         break;
+    case kWidget::Image:
+        m_widget = std::make_unique<WidgetImage>();
+        break;
     }
     
     while (attr)