address open dialog delay issue

Author: brtnfld

hdfview/src/main/java/hdf/view/HDFView.java

@@ -516,7 +516,7 @@ public void widgetDisposed(DisposeEvent e)
         log.info("Main Window created");
 
         // Start background class warm-up for all platforms
-        startBackgroundClassWarmup();
+        startBackgroundClassWarmup(shell);
 
         return shell;
     }
@@ -1075,8 +1075,8 @@ private void setupMacOSMenuHandlers(final Shell shell)
                     // Hook up the "About HDFView" menu item
                     item.addListener(SWT.Selection, event -> {
                         log.debug("macOS About menu triggered");
-                        // Use timerExec to allow the OS menu to close before opening the dialog
-                        display.timerExec(10, () -> {
+                        // Use timerExec with 100ms delay to allow macOS menu animation to complete
+                        display.timerExec(100, () -> {
                             if (!shell.isDisposed()) {
                                 new AboutDialog(shell).open();
                             }
@@ -1087,8 +1087,8 @@ else if (id == SWT.ID_PREFERENCES) {
                     // Hook up the "Preferences..." menu item
                     item.addListener(SWT.Selection, event -> {
                         log.debug("macOS Preferences menu triggered");
-                        // Use timerExec to allow the OS menu to close before opening the dialog
-                        display.timerExec(10, () -> {
+                        // Use timerExec with 100ms delay to allow macOS menu animation to complete
+                        display.timerExec(100, () -> {
                             if (!shell.isDisposed()) {
                                 openUserOptionsDialog(shell);
                             }
@@ -1105,33 +1105,53 @@ else if (id == SWT.ID_PREFERENCES) {
     }
 
     /**
-     * Starts a background thread to pre-load User Options dialog classes.
-     * This prevents UI freezes when the user first opens the preferences dialog.
-     * The warm-up runs at low priority to avoid impacting application startup.
+     * Schedules background pre-creation of the User Options dialog on the UI thread.
+     * This eliminates the 2-3 second freeze when the user first clicks Preferences.
+     * The dialog is created in the background after startup, then cached for instant reuse.
+     *
+     * @param shell the main shell (used to access the Display and as parent for dialog)
      */
-    private void startBackgroundClassWarmup()
+    private void startBackgroundClassWarmup(final Shell shell)
     {
-        Thread warmUpThread = new Thread(() -> {
+        final Display display = shell.getDisplay();
+
+        // Schedule dialog creation on the UI thread after a 2-second delay
+        // This delay ensures the UI is fully initialized and startup is complete
+        display.timerExec(2000, () -> {
+            if (shell.isDisposed()) {
+                return; // Don't run if the shell was closed during the delay
+            }
+
             try {
-                // Force JVM to load and verify these classes now, instead of waiting for the user to
-                // click.
-                Class.forName("org.eclipse.jface.preference.PreferenceManager");
-                Class.forName("org.eclipse.jface.preference.PreferenceDialog");
-                Class.forName("hdf.view.UserOptionsDialog");
-                Class.forName("hdf.view.UserOptionsNode");
-                Class.forName("hdf.view.UserOptionsGeneralPage");
-                Class.forName("hdf.view.UserOptionsHDFPage");
-                Class.forName("hdf.view.UserOptionsViewModulesPage");
+                log.debug("Pre-creating User Options dialog in background...");
+
+                // Pre-create the entire dialog structure (this is what takes 2-3 seconds)
+                // The dialog will be cached and reused when the user clicks Preferences
+                PreferenceManager mgr = new PreferenceManager();
+
+                UserOptionsNode generalNode = new UserOptionsNode("general", new UserOptionsGeneralPage());
+                UserOptionsNode hdfNode     = new UserOptionsNode("hdf", new UserOptionsHDFPage());
+                UserOptionsNode modulesNode = new UserOptionsNode("modules", new UserOptionsViewModulesPage());
+
+                mgr.addToRoot(generalNode);
+                mgr.addToRoot(hdfNode);
+                mgr.addToRoot(modulesNode);
+
+                userOptionDialog = new UserOptionsDialog(shell, mgr, rootDir);
+                userOptionDialog.setPreferenceStore(props);
+                userOptionDialog.create(); // This creates all the SWT widgets (expensive!)
+
+                log.info("User Options dialog pre-created successfully - first open will be instant");
             }
             catch (Throwable t) {
-                // Ignore errors during warm-up; they will be handled normally if they persist
+                // If pre-creation fails, the dialog will be created on-demand when user clicks
+                log.warn("Failed to pre-create User Options dialog (will create on-demand): {}",
+                         t.getMessage());
+                userOptionDialog = null; // Ensure we don't keep a broken reference
             }
         });
-        warmUpThread.setDaemon(true); // Ensure this thread doesn't prevent app exit
-        warmUpThread.setPriority(Thread.MIN_PRIORITY);
-        warmUpThread.start();
 
-        log.debug("Background class warm-up thread started");
+        log.debug("Background dialog pre-creation scheduled");
     }
 
     /**
@@ -1142,27 +1162,39 @@ private void startBackgroundClassWarmup()
      */
     private void openUserOptionsDialog(Shell parentShell)
     {
-        // Create the preference manager
-        PreferenceManager mgr = new PreferenceManager();
+        // Check if we have a pre-created dialog that's still valid
+        boolean needsCreation = (userOptionDialog == null) ||
+                                (userOptionDialog.getShell() != null &&
+                                 userOptionDialog.getShell().isDisposed());
+
+        if (needsCreation) {
+            log.debug("Creating User Options dialog (first open or after disposal)...");
+
+            // Create the preference manager
+            PreferenceManager mgr = new PreferenceManager();
 
-        // Create the preference nodes with semantic names
-        UserOptionsNode generalNode = new UserOptionsNode("general", new UserOptionsGeneralPage());
-        UserOptionsNode hdfNode     = new UserOptionsNode("hdf", new UserOptionsHDFPage());
-        UserOptionsNode modulesNode = new UserOptionsNode("modules", new UserOptionsViewModulesPage());
+            // Create the preference nodes with semantic names
+            UserOptionsNode generalNode = new UserOptionsNode("general", new UserOptionsGeneralPage());
+            UserOptionsNode hdfNode     = new UserOptionsNode("hdf", new UserOptionsHDFPage());
+            UserOptionsNode modulesNode = new UserOptionsNode("modules", new UserOptionsViewModulesPage());
 
-        // Add the nodes
-        mgr.addToRoot(generalNode);
-        mgr.addToRoot(hdfNode);
-        mgr.addToRoot(modulesNode);
+            // Add the nodes
+            mgr.addToRoot(generalNode);
+            mgr.addToRoot(hdfNode);
+            mgr.addToRoot(modulesNode);
 
-        // Create the preferences dialog using the provided parent shell
-        userOptionDialog = new UserOptionsDialog(parentShell, mgr, rootDir);
+            // Create the preferences dialog using the provided parent shell
+            userOptionDialog = new UserOptionsDialog(parentShell, mgr, rootDir);
 
-        // Set the preference store
-        userOptionDialog.setPreferenceStore(props);
-        userOptionDialog.create();
+            // Set the preference store
+            userOptionDialog.setPreferenceStore(props);
+            userOptionDialog.create();
+        }
+        else {
+            log.debug("Reusing pre-created User Options dialog (instant open)");
+        }
 
-        // Open the dialog
+        // Open the dialog (instant if pre-created, or newly created if needed)
         userOptionDialog.open();
 
         // TODO(HDFView) [2025-01]: TECHNICAL DEBT - Fix work directory change detection