image widget

many assumptions about X backed were made, to be refined if does not
work properly in some setups

common/utils/T/tracer/gui/widget.c

@@ -265,7 +265,7 @@ void widget_dirty(gui *_gui, widget *_this)
 
 static const char *names[] = {
   "TOPLEVEL_WINDOW", "CONTAINER", "POSITIONER", "TEXT_LIST",
-  "XY_PLOT", "BUTTON", "LABEL", "TIMELINE", "SPACE"
+  "XY_PLOT", "BUTTON", "LABEL", "TIMELINE", "SPACE", "IMAGE"
 };
 const char *widget_name(enum widget_type type)
 {
@@ -279,6 +279,7 @@ const char *widget_name(enum widget_type type)
   case LABEL:
   case TIMELINE:
   case SPACE:
+  case IMAGE:
     return names[type];
   }
   return "UNKNOWN (error)";