8346607: IGV: Support drag-and-drop for opening graph files

src/utils/IdealGraphVisualizer/Coordinator/src/main/java/com/sun/hotspot/igv/coordinator/OutlineTopComponent.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2008, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -37,8 +37,18 @@
 import com.sun.hotspot.igv.settings.Settings;
 import com.sun.hotspot.igv.util.LookupHistory;
 import com.sun.hotspot.igv.view.EditorTopComponent;
+import com.sun.hotspot.igv.view.PlaceholderTopComponent;
 import java.awt.BorderLayout;
 import java.awt.Dimension;
+import java.awt.HeadlessException;
+import java.awt.datatransfer.DataFlavor;
+import java.awt.datatransfer.UnsupportedFlavorException;
+import java.awt.dnd.DnDConstants;
+import java.awt.dnd.DropTarget;
+import java.awt.dnd.DropTargetDragEvent;
+import java.awt.dnd.DropTargetDropEvent;
+import java.awt.dnd.DropTargetEvent;
+import java.awt.dnd.DropTargetListener;
 import java.io.*;
 import java.nio.channels.FileChannel;
 import java.nio.file.*;
@@ -92,6 +102,9 @@ public final class OutlineTopComponent extends TopComponent implements ExplorerM
     private GraphNode[] selectedGraphs = new GraphNode[0];
     private Path documentPath = null;
 
+    private final DropTargetListener fileDropListener = new FileDropListener();
+    private final PlaceholderTopComponent editorPlaceholder = new PlaceholderTopComponent(fileDropListener);
+
     private OutlineTopComponent() {
         initComponents();
 
@@ -100,6 +113,17 @@ private OutlineTopComponent() {
         initListView();
         initToolbar();
         server.startServer();
+
+        showEditorPlaceholder();
+
+        WindowManager.getDefault().invokeWhenUIReady(() -> {
+           new DropTarget(WindowManager.getDefault().getMainWindow(), fileDropListener);
+        });
+    }
+
+    private void showEditorPlaceholder() {
+        editorPlaceholder.open();
+        editorPlaceholder.requestActive();
     }
 
     public static GraphDocument getDocument() {
@@ -236,6 +260,11 @@ private void documentChanged() {
         saveAction.setEnabled(enableButton);
         saveAsAction.setEnabled(enableButton);
         removeAllAction.setEnabled(enableButton);
+        if (document.getElements().isEmpty()) {
+            showEditorPlaceholder();
+        } else {
+            editorPlaceholder.close();
+        }
     }
 
     @Override
@@ -372,15 +401,20 @@ public void openFile() {
         JFileChooser fc = new JFileChooser(Settings.get().get(Settings.DIRECTORY, Settings.DIRECTORY_DEFAULT));
         fc.setFileFilter(graphFileFilter);
         if (fc.showOpenDialog(null) == JFileChooser.APPROVE_OPTION) {
-            clearWorkspace();
-            String path = fc.getSelectedFile().getAbsolutePath();
-            Settings.get().put(Settings.DIRECTORY, path);
-            setDocumentPath(path);
-            try {
-                loadGraphDocument(path, true);
-            } catch (IOException e) {
-                throw new RuntimeException(e);
-            }
+            handleOpen(fc.getSelectedFile());
+        }
+    }
+
+    private void handleOpen(File file) {
+        clearWorkspace();
+        editorPlaceholder.close();
+        String path = file.getAbsolutePath();
+        Settings.get().put(Settings.DIRECTORY, path);
+        setDocumentPath(path);
+        try {
+            loadGraphDocument(path, true);
+        } catch (IOException e) {
+            throw new RuntimeException(e);
         }
     }
 
@@ -590,6 +624,65 @@ public void setState(String state) {
         handle.finish();
     }
 
+    private class FileDropListener implements DropTargetListener {
+        @Override
+        public void dragEnter(DropTargetDragEvent dtde) {
+            if (dtde.isDataFlavorSupported(DataFlavor.javaFileListFlavor)) {
+                dtde.acceptDrag(DnDConstants.ACTION_COPY);
+            } else {
+                dtde.rejectDrag();
+            }
+        }
+
+        @Override
+        public void dragOver(DropTargetDragEvent dtde) {
+            dragEnter(dtde);
+        }
+
+        @Override
+        public void dropActionChanged(DropTargetDragEvent dtde) {}
+
+        @Override
+        public void dragExit(DropTargetEvent dte) {}
+
+        @Override
+        public void drop(DropTargetDropEvent dtde) {
+            try {
+                if (dtde.isDataFlavorSupported(DataFlavor.javaFileListFlavor)) {
+                    dtde.acceptDrop(DnDConstants.ACTION_COPY);
+
+                    List<File> droppedFiles = (List<File>) dtde.getTransferable()
+                            .getTransferData(DataFlavor.javaFileListFlavor);
+
+                    if (droppedFiles.isEmpty()) return;
+                    if (droppedFiles.size() > 1) {
+                        JOptionPane.showMessageDialog(null,
+                                "Please only drag and drop one file as only one file can be open at a time.",
+                                "Multiple Files Dropped", JOptionPane.WARNING_MESSAGE);
+                        return;
+                    }
+
+                    File file = droppedFiles.get(0);
+
+                    if (file.getName().endsWith(".xml") || file.getName().endsWith(".igv")) {
+                        handleOpen(file);
+                    } else {
+                        JOptionPane.showMessageDialog(null,
+                                "Unsupported file type: " + file.getName(),
+                                "Unsupported File", JOptionPane.WARNING_MESSAGE);
+                    }
+
+                    dtde.dropComplete(true);
+                } else {
+                    dtde.rejectDrop();
+                }
+            } catch (HeadlessException | UnsupportedFlavorException | IOException ex) {
+                ex.printStackTrace();
+                dtde.dropComplete(false);
+            }
+        }
+    }
+
     /** This method is called from within the constructor to
      * initialize the form.
      * WARNING: Do NOT modify this code. The content of this method is

src/utils/IdealGraphVisualizer/View/src/main/java/com/sun/hotspot/igv/view/PlaceholderTopComponent.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+package com.sun.hotspot.igv.view;
+
+import java.awt.BorderLayout;
+import java.awt.dnd.DropTarget;
+import java.awt.dnd.DropTargetListener;
+import javax.swing.JLabel;
+import javax.swing.JPanel;
+import javax.swing.SwingConstants;
+import org.openide.windows.TopComponent;
+
+/**
+ * This TopComponent is displayed in the editor location if no graphs have been loaded
+ * and allows the user to easily drag and drop graph files to be opened.
+ */
+public class PlaceholderTopComponent extends TopComponent {
+    public PlaceholderTopComponent(DropTargetListener fileDropListener) {
+        setLayout(new BorderLayout());
+        JPanel container = new JPanel(new BorderLayout());
+        container.add(new JLabel("Drop file here to open", SwingConstants.CENTER), BorderLayout.CENTER);
+        container.setDropTarget(new DropTarget(container, fileDropListener));
+        add(container, BorderLayout.CENTER);
+        setName("Welcome");
+    }
+}