handle X Expose, GraphicsExpose, and MapNotify events

src/gui/jtk/Jtk_event.cc

@@ -350,7 +350,16 @@ static bool ProcessXEvent(XEvent * x_event, Jtk_Event * event)
         break;
 
     case Expose:
-        break;
+        event->type = JTK_EVENT_WINDOW_EXPOSE;
+        return true;
+
+    case GraphicsExpose:
+        event->type = JTK_EVENT_WINDOW_EXPOSE;
+        return true;
+
+    case MapNotify:
+        event->type = JTK_EVENT_WINDOW_EXPOSE;
+        return true;
 
     case ConfigureNotify:
         return ProcessConfigureEvent(x_event, event);