Use WindowListener instead than FocusListener to spawn watcher

This ensures that watcher is inactive when children views are focused
Solves #6827

Author: facchinm

Diff for: app/src/processing/app/Editor.java

@@ -86,7 +86,7 @@
  * Main editor panel for the Processing Development Environment.
  */
 @SuppressWarnings("serial")
-public class Editor extends JFrame implements RunnerListener, FocusListener {
+public class Editor extends JFrame implements RunnerListener {
 
   public static final int MAX_TIME_AWAITING_FOR_RESUMING_SERIAL_MONITOR = 10000;
 
@@ -237,12 +237,20 @@ public void windowClosing(WindowEvent e) {
     // When bringing a window to front, let the Base know
     addWindowListener(new WindowAdapter() {
         public void windowActivated(WindowEvent e) {
+          if (watcher != null) {
+            watcher.interrupt();
+            watcher = null;
+          }
           base.handleActivated(Editor.this);
         }
 
         // added for 1.0.5
         // http://dev.processing.org/bugs/show_bug.cgi?id=1260
         public void windowDeactivated(WindowEvent e) {
+          if (watcher == null) {
+            watcher = new Thread(task);
+            watcher.start();
+          }
           fileMenu.remove(sketchbookMenu);
           fileMenu.remove(examplesMenu);
           List<Component> toolsMenuItemsToRemove = new LinkedList<>();
@@ -359,22 +367,6 @@ public void windowDeactivated(WindowEvent e) {
     EditorConsole.setCurrentEditorConsole(console);
   }
 
-  @Override
-  public void focusGained(FocusEvent fe){
-    if (watcher != null) {
-      watcher.interrupt();
-      watcher = null;
-    }
-  }
-
-  @Override
-  public void focusLost(FocusEvent fe){
-    if (watcher == null) {
-      watcher = new Thread(task);
-      watcher.start();
-    }
-  }
-
   /**
    * Handles files dragged & dropped from the desktop and into the editor
    * window. Dragging files into the editor window is the same as using
@@ -2012,10 +2004,6 @@ public void run() {
       }
     };
 
-    addFocusListener(this);
-    getTabs().forEach(tab -> tab.getScrollPane().addFocusListener(this));
-    getTabs().forEach(tab -> tab.getTextArea().addFocusListener(this));
-
     // opening was successful
     return true;
   }