Fix theme switching exception

CHANGELOG.md

@@ -46,6 +46,7 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 - We fixed an issue where the exception that there are invalid characters in filename. [#8786](https://github.com/JabRef/jabref/issues/8786)
 - When the proxy configuration removed the proxy user/password, this change is applied immediately.
 - We fixed an issue where removing several groups deletes only one of them. [#8390](https://github.com/JabRef/jabref/issues/8390)
+- We fixed a bug where switching between themes will cause an error/exception. [#8939](https://github.com/JabRef/jabref/pull/8939)
 
 ### Removed
 

src/main/java/org/jabref/gui/JabRefDialogService.java

@@ -80,7 +80,6 @@ public JabRefDialogService(Window mainWindow, Pane mainPane, ThemeManager themeM
 
     private FXDialog createDialog(AlertType type, String title, String content) {
         FXDialog alert = new FXDialog(type, title, true);
-        themeManager.installCss(alert.getDialogPane().getScene());
         alert.setHeaderText(null);
         alert.setContentText(content);
         alert.getDialogPane().setMinHeight(Region.USE_PREF_SIZE);
@@ -113,7 +112,6 @@ protected Node createDetailsButton() {
 
         // Reset the dialog graphic using the default style
         alert.getDialogPane().setGraphic(graphic);
-        themeManager.installCss(alert.getDialogPane().getScene());
         alert.setHeaderText(null);
         alert.setContentText(content);
         alert.getDialogPane().setMinHeight(Region.USE_PREF_SIZE);
@@ -138,7 +136,6 @@ public <T> Optional<T> showChoiceDialogAndWait(String title, String content, Str
         choiceDialog.setTitle(title);
         choiceDialog.setContentText(content);
         choiceDialog.initOwner(mainWindow);
-        themeManager.installCss(choiceDialog.getDialogPane().getScene());
         return choiceDialog.showAndWait();
     }
 
@@ -148,7 +145,6 @@ public Optional<String> showInputDialogAndWait(String title, String content) {
         inputDialog.setHeaderText(title);
         inputDialog.setContentText(content);
         inputDialog.initOwner(mainWindow);
-        themeManager.installCss(inputDialog.getDialogPane().getScene());
         return inputDialog.showAndWait();
     }
 
@@ -158,7 +154,6 @@ public Optional<String> showInputDialogWithDefaultAndWait(String title, String c
         inputDialog.setHeaderText(title);
         inputDialog.setContentText(content);
         inputDialog.initOwner(mainWindow);
-        themeManager.installCss(inputDialog.getDialogPane().getScene());
         return inputDialog.showAndWait();
     }
 
@@ -186,7 +181,6 @@ public void showErrorDialogAndWait(String message, Throwable exception) {
         exceptionDialog.getDialogPane().setMaxWidth(mainWindow.getWidth() / 2);
         exceptionDialog.setHeaderText(message);
         exceptionDialog.initOwner(mainWindow);
-        themeManager.installCss(exceptionDialog.getDialogPane().getScene());
         exceptionDialog.showAndWait();
     }
 
@@ -196,7 +190,6 @@ public void showErrorDialogAndWait(String title, String content, Throwable excep
         exceptionDialog.setHeaderText(title);
         exceptionDialog.setContentText(content);
         exceptionDialog.initOwner(mainWindow);
-        themeManager.installCss(exceptionDialog.getDialogPane().getScene());
         exceptionDialog.showAndWait();
     }
 
@@ -266,7 +259,6 @@ public Optional<ButtonType> showCustomDialogAndWait(String title, DialogPane con
         alert.getDialogPane().setMinHeight(Region.USE_PREF_SIZE);
         alert.setResizable(true);
         alert.initOwner(mainWindow);
-        themeManager.installCss(alert.getDialogPane().getScene());
         return alert.showAndWait();
     }
 
@@ -294,7 +286,6 @@ public <V> void showProgressDialog(String title, String content, Task<V> task) {
             task.cancel();
             progressDialog.close();
         });
-        themeManager.installCss(progressDialog.getDialogPane().getScene());
         progressDialog.initOwner(mainWindow);
         progressDialog.show();
     }
@@ -319,7 +310,6 @@ public <V> Optional<ButtonType> showBackgroundProgressDialogAndWait(String title
         alert.getDialogPane().setMinHeight(Region.USE_PREF_SIZE);
         alert.setResizable(true);
         alert.initOwner(mainWindow);
-        themeManager.installCss(alert.getDialogPane().getScene());
 
         stateManager.getAnyTasksThatWillNotBeRecoveredRunning().addListener((observable, oldValue, newValue) -> {
             if (!newValue) {

src/main/java/org/jabref/gui/theme/ThemeManager.java

@@ -6,6 +6,7 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.Set;
 import java.util.WeakHashMap;
 import java.util.function.Consumer;
@@ -46,7 +47,7 @@ public class ThemeManager {
     private final StyleSheet baseStyleSheet;
     private Theme theme;
 
-    private final Set<Scene> scenes = Collections.newSetFromMap(new WeakHashMap<>());
+    private Scene mainWindowScene;
     private final Set<WebEngine> webEngines = Collections.newSetFromMap(new WeakHashMap<>());
 
     public ThemeManager(AppearancePreferences appearancePreferences,
@@ -88,8 +89,7 @@ private void updateThemeSettings() {
     }
 
     private void updateFontSettings() {
-        DefaultTaskExecutor.runInJavaFXThread(() ->
-                updateRunner.accept(() -> scenes.forEach(this::updateFontStyle)));
+        DefaultTaskExecutor.runInJavaFXThread(() -> updateRunner.accept(() -> getMainWindowScene().ifPresent(this::updateFontStyle)));
     }
 
     private void removeStylesheetFromWatchList(StyleSheet styleSheet) {
@@ -117,12 +117,10 @@ private void baseCssLiveUpdate() {
         if (baseStyleSheet.getSceneStylesheet() == null) {
             LOGGER.error("Base stylesheet does not exist.");
         } else {
-            LOGGER.debug("Updating base CSS for {} scenes", scenes.size());
+            LOGGER.debug("Updating base CSS for main window scene");
         }
 
-        DefaultTaskExecutor.runInJavaFXThread(() ->
-                updateRunner.accept(() -> scenes.forEach(this::updateBaseCss))
-        );
+        DefaultTaskExecutor.runInJavaFXThread(() -> updateRunner.accept(this::updateBaseCss));
     }
 
     private void additionalCssLiveUpdate() {
@@ -131,11 +129,11 @@ private void additionalCssLiveUpdate() {
             return styleSheet.getWebEngineStylesheet();
         }).orElse("");
 
-        LOGGER.debug("Updating additional CSS for {} scenes and {} web engines", scenes.size(), webEngines.size());
+        LOGGER.debug("Updating additional CSS for main window scene and {} web engines", webEngines.size());
 
         DefaultTaskExecutor.runInJavaFXThread(() ->
                 updateRunner.accept(() -> {
-                    scenes.forEach(this::updateAdditionalCss);
+                    updateAdditionalCss();
 
                     webEngines.forEach(webEngine -> {
                         // force refresh by unloading style sheet, if the location hasn't changed
@@ -148,17 +146,19 @@ private void additionalCssLiveUpdate() {
         );
     }
 
-    private void updateBaseCss(Scene scene) {
-        List<String> stylesheets = scene.getStylesheets();
-        if (!stylesheets.isEmpty()) {
-            stylesheets.remove(0);
-        }
+    private void updateBaseCss() {
+        getMainWindowScene().ifPresent(scene -> {
+            List<String> stylesheets = scene.getStylesheets();
+            if (!stylesheets.isEmpty()) {
+                stylesheets.remove(0);
+            }
 
-        stylesheets.add(0, baseStyleSheet.getSceneStylesheet().toExternalForm());
+            stylesheets.add(0, baseStyleSheet.getSceneStylesheet().toExternalForm());
+        });
     }
 
-    private void updateAdditionalCss(Scene scene) {
-        scene.getStylesheets().setAll(List.of(
+    private void updateAdditionalCss() {
+        getMainWindowScene().ifPresent(scene -> scene.getStylesheets().setAll(List.of(
                 baseStyleSheet.getSceneStylesheet().toExternalForm(),
                 appearancePreferences.getTheme()
                                      .getAdditionalStylesheet().map(styleSheet -> {
@@ -170,21 +170,21 @@ private void updateAdditionalCss(Scene scene) {
                                          }
                                      })
                                      .orElse("")
-        ));
+        )));
     }
 
     /**
      * Installs the base css file as a stylesheet in the given scene. Changes in the css file lead to a redraw of the
      * scene using the new css file.
      *
-     * @param scene the scene to install the css into
+     * @param mainWindowScene the scene to install the css into
      */
-    public void installCss(Scene scene) {
+    public void installCss(Scene mainWindowScene) {
+        Objects.requireNonNull(mainWindowScene, "scene is required");
         updateRunner.accept(() -> {
-            if (this.scenes.add(scene)) {
-                updateBaseCss(scene);
-                updateAdditionalCss(scene);
-            }
+            this.mainWindowScene = mainWindowScene;
+            updateBaseCss();
+            updateAdditionalCss();
         });
     }
 
@@ -223,4 +223,8 @@ public void updateFontStyle(Scene scene) {
     public Theme getActiveTheme() {
         return this.theme;
     }
+
+    public Optional<Scene> getMainWindowScene() {
+        return Optional.ofNullable(mainWindowScene);
+    }
 }

src/main/java/org/jabref/gui/util/BaseDialog.java

@@ -2,7 +2,6 @@
 
 import java.util.Optional;
 
-import javafx.scene.Node;
 import javafx.scene.control.Button;
 import javafx.scene.control.ButtonType;
 import javafx.scene.control.Dialog;
@@ -15,8 +14,6 @@
 import org.jabref.gui.keyboard.KeyBinding;
 import org.jabref.gui.keyboard.KeyBindingRepository;
 
-import com.tobiasdiez.easybind.EasyBind;
-
 public class BaseDialog<T> extends Dialog<T> implements org.jabref.gui.Dialog<T> {
 
     protected BaseDialog() {
@@ -39,10 +36,6 @@ protected BaseDialog() {
 
         setDialogIcon(IconTheme.getJabRefImage());
         setResizable(true);
-
-        EasyBind.wrapNullable(dialogPaneProperty())
-                .mapObservable(Node::sceneProperty)
-                .subscribeToValues(scene -> Globals.getThemeManager().installCss(scene));
     }
 
     private Optional<Button> getDefaultButton() {