Canvas: add method clearFocusElement.

simgear/canvas/Canvas.cxx

@@ -212,6 +212,12 @@ namespace canvas
     _focus_element = el;
   }
 
+  //----------------------------------------------------------------------------
+  void Canvas::clearFocusElement()
+  {
+    _focus_element.reset();
+  }
+
   //----------------------------------------------------------------------------
   void Canvas::enableRendering(bool force)
   {

simgear/canvas/Canvas.hxx

@@ -145,6 +145,13 @@ namespace canvas
        */
       void setFocusElement(const ElementPtr& el);
 
+      /**
+       * Clear the focus element.
+       *
+       * @see setFocusElement()
+       */
+      void clearFocusElement();
+
       /**
        * Enable rendering for the next frame
        *

simgear/canvas/elements/CanvasText.cxx

@@ -28,7 +28,6 @@ namespace simgear
 {
 namespace canvas
 {
-  class TextLine;
   class Text::TextOSG:
     public osgText::Text
   {