Implement wait cursor delay for TreeView.

 - initial delay for wait cursor activation on tree node expansion
 - AutoClosable for convenience reasons, in case this is one day
   extracted into a utility

Co-authored-by: Laszlo Kishalmi <laszlo.kishalmi@gmail.com>

Author: mbien

platform/openide.explorer/src/org/openide/explorer/view/TreeView.java

@@ -83,6 +83,7 @@
 import javax.swing.KeyStroke;
 import javax.swing.ScrollPaneLayout;
 import javax.swing.SwingUtilities;
+import javax.swing.Timer;
 import javax.swing.ToolTipManager;
 import javax.swing.TransferHandler;
 import javax.swing.UIManager;
@@ -915,73 +916,61 @@ public void setAutoWaitCursor(boolean enable) {
         autoWaitCursor = enable;
     }
 
-    //
-    // showing and removing the wait cursor
-    //
-    private void showWaitCursor (boolean show) {
-        JRootPane rPane = getRootPane();
-        if (rPane == null) {
+    private void maybeShowWaitCursor(Node node) {
+        if (node == null || !autoWaitCursor) {
             return;
         }
-
-        if (SwingUtilities.isEventDispatchThread()) {
-            doShowWaitCursor(rPane.getGlassPane(), show);
-        } else {
-            SwingUtilities.invokeLater(new CursorR(rPane.getGlassPane(), show));
-        }
+        // not sure whenter throughput 1 is OK...
+        ViewUtil.uiProcessor().post(() -> {
+            try (DelayedWaitCursor cursor = new DelayedWaitCursor(getRootPane())) {
+                cursor.enable();
+                node.getChildren().getNodesCount(true); // blocks until expanded
+            } catch (Exception e) {
+                LOG.log(Level.WARNING, "can't determine node count", e);
+            }
+        });
     }
 
-    private static void doShowWaitCursor (Component glassPane, boolean show) {
-        if (show) {
-            glassPane.setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
-            glassPane.setVisible(true);
-        } else {
-            glassPane.setVisible(false);
-            glassPane.setCursor(null);
-        }
-    }
+    /// Shows the wait cursor after an initial delay.
+    /// Can be used in ARM-blocks.
+    private static class DelayedWaitCursor implements AutoCloseable {
 
-    private static class CursorR implements Runnable {
-        private Component glassPane;
-        private boolean show;
+        private static final int DELAY = 200;
 
-        private CursorR(Component cont, boolean show) {
-            this.glassPane = cont;
-            this.show = show;
-        }
+        private final JRootPane root;
+        private final Timer timer;
 
-        @Override
-        public void run() {
-            doShowWaitCursor(glassPane, show);
+        private DelayedWaitCursor(JRootPane root) {
+            this.root = root;
+            timer = new Timer(DELAY, (e) -> {
+                if (root != null) {
+                    root.getGlassPane().setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
+                    root.getGlassPane().setVisible(true);
+                }
+            });
+            timer.setRepeats(false);
         }
-    }
 
-    private void prepareWaitCursor(final Node node) {
-        // check type of node
-        if (node == null || !autoWaitCursor) {
-            return;
+        private void enable() {
+            timer.start();
         }
 
-        showWaitCursor(true);
-        // not sure whenter throughput 1 is OK...
-        ViewUtil.uiProcessor().post(new Runnable() {
-            @Override
-            public void run() {
-                try {
-                    node.getChildren().getNodesCount(true);
-                } catch (Exception e) {
-                    // log a exception
-                    LOG.log(Level.WARNING, null, e);
-                } finally {
-                    // show normal cursor above all
-                    showWaitCursor(false);
+        private void disable() {
+            timer.stop();
+            SwingUtilities.invokeLater(() -> {
+                if (root != null) {
+                    root.getGlassPane().setVisible(false);
+                    root.getGlassPane().setCursor(null);
                 }
-            }
-        });
+            });
+        }
+
+        @Override
+        public void close() {
+            disable();
+        }
     }
-    
-   
-    
+
     /** Synchronize the selected nodes from the manager of this Explorer.
     * The default implementation does nothing.
     */
@@ -1499,7 +1488,7 @@ public void treeWillExpand(TreeExpansionEvent event)
         throws ExpandVetoException {
             // prepare wait cursor and optionally show it
             TreePath path = event.getPath();
-            prepareWaitCursor(DragDropUtilities.secureFindNode(path.getLastPathComponent()));
+            maybeShowWaitCursor(DragDropUtilities.secureFindNode(path.getLastPathComponent()));
         }
     }
      // end of TreePropertyListener