Scope default theme preference by product or application

The default theme preference is now stored under a product-specific
(or application-specific) sub-node in user scope. This allows different
Eclipse-based products sharing the same user preferences location to
maintain independent theme defaults.

When reading the preference, the product ID (from Platform.getProduct())
is used as the sub-node key. If no product is configured, the application
ID (eclipse.application system property) is used as fallback. If neither
is available, the preference is stored at the base node level.

This also migrates the 'Manage default theme' dialog from
ConfigurationScope to UserScope to be consistent with the rest of the
theme preference handling.

Author: vogella

bundles/org.eclipse.e4.ui.workbench.swt/src/org/eclipse/e4/ui/internal/workbench/swt/E4Application.java

@@ -317,9 +317,16 @@ private void setCSSContextVariables(IApplicationContext applicationContext, IEcl
 				: getArgValue(E4Application.THEME_ID, applicationContext, false);
 
 		if (!themeId.isPresent() && !cssURI.isPresent()) {
-			IEclipsePreferences userScopeNode = UserScope.INSTANCE
+			IEclipsePreferences themeNode = UserScope.INSTANCE
 					.getNode("org.eclipse.e4.ui.css.swt.theme");
-			String defaultThemeId = userScopeNode.get("themeid", DEFAULT_THEME_ID);
+			String productOrAppId = getProductOrApplicationId();
+			String defaultThemeId = null;
+			if (productOrAppId != null) {
+				defaultThemeId = themeNode.node(productOrAppId).get("themeid", null);
+			}
+			if (defaultThemeId == null) {
+				defaultThemeId = DEFAULT_THEME_ID;
+			}
 			context.set(E4Application.THEME_ID, defaultThemeId);
 		} else {
 			context.set(E4Application.THEME_ID, themeId.orElseGet(() -> null));
@@ -403,6 +410,19 @@ private URI determineApplicationModelURI(IApplicationContext appContext) {
 
 	}
 
+	/**
+	 * Returns the product ID if a product is configured, otherwise falls back to
+	 * the application ID from the system property. Returns {@code null} if
+	 * neither is available.
+	 */
+	private static String getProductOrApplicationId() {
+		IProduct product = Platform.getProduct();
+		if (product != null) {
+			return product.getId();
+		}
+		return System.getProperty("eclipse.application"); //$NON-NLS-1$
+	}
+
 	/**
 	 * Finds an argument's value in the app's command line arguments, branding,
 	 * and system properties

bundles/org.eclipse.ui.workbench/eclipseui/org/eclipse/ui/internal/dialogs/ViewsPreferencePage.java

@@ -35,6 +35,7 @@
 import org.eclipse.core.runtime.IExtension;
 import org.eclipse.core.runtime.IExtensionPoint;
 import org.eclipse.core.runtime.IExtensionRegistry;
+import org.eclipse.core.runtime.IProduct;
 import org.eclipse.core.runtime.Platform;
 import org.eclipse.core.runtime.Platform.OS;
 import org.eclipse.core.runtime.RegistryFactory;
@@ -339,8 +340,11 @@ private ITheme getSelectedTheme() {
 	}
 
 	private void openManageDefaultThemeDialog() {
-		IEclipsePreferences configNode = ConfigurationScope.INSTANCE.getNode(E4_THEME_EXTENSION_POINT);
-		String currentDefaultId = configNode.get("themeid", null); //$NON-NLS-1$
+		String productOrAppId = getProductOrApplicationId();
+		IEclipsePreferences baseNode = UserScope.INSTANCE.getNode(E4_THEME_EXTENSION_POINT);
+		IEclipsePreferences scopedNode = productOrAppId != null ? (IEclipsePreferences) baseNode.node(productOrAppId)
+				: baseNode;
+		String currentDefaultId = scopedNode.get("themeid", null); //$NON-NLS-1$
 
 		String currentDefaultLabel = null;
 		if (currentDefaultId != null) {
@@ -377,23 +381,36 @@ private void openManageDefaultThemeDialog() {
 		int result = dialog.open();
 		if (result == 0 && selectedTheme != null) {
 			// Set as default
-			configNode.put("themeid", selectedTheme.getId()); //$NON-NLS-1$
+			scopedNode.put("themeid", selectedTheme.getId()); //$NON-NLS-1$
 			try {
-				configNode.flush();
+				scopedNode.flush();
 			} catch (BackingStoreException e) {
-				WorkbenchPlugin.log("Failed to set default theme in configuration scope", e); //$NON-NLS-1$
+				WorkbenchPlugin.log("Failed to set default theme in user scope", e); //$NON-NLS-1$
 			}
 		} else if (currentDefaultId != null && result == 1) {
 			// Remove default
-			configNode.remove("themeid"); //$NON-NLS-1$
+			scopedNode.remove("themeid"); //$NON-NLS-1$
 			try {
-				configNode.flush();
+				scopedNode.flush();
 			} catch (BackingStoreException e) {
-				WorkbenchPlugin.log("Failed to remove default theme from configuration scope", e); //$NON-NLS-1$
+				WorkbenchPlugin.log("Failed to remove default theme from user scope", e); //$NON-NLS-1$
 			}
 		}
 	}
 
+	/**
+	 * Returns the product ID if a product is configured, otherwise falls back to
+	 * the application ID from the system property. Returns {@code null} if
+	 * neither is available.
+	 */
+	private static String getProductOrApplicationId() {
+		IProduct product = Platform.getProduct();
+		if (product != null) {
+			return product.getId();
+		}
+		return System.getProperty("eclipse.application"); //$NON-NLS-1$
+	}
+
 	@Override
 	public void init(IWorkbench workbench) {
 		MApplication application = workbench.getService(MApplication.class);
@@ -521,11 +538,15 @@ protected Control createCustomArea(Composite parent) {
 		int result = dialog.open();
 		if (result == 0 || result == 1) { // 0: Restart, 1: Don't Restart
 			if (themeId != null && useAsDefault[0]) {
-				IEclipsePreferences userScopeNode = UserScope.INSTANCE
+				IEclipsePreferences baseNode = UserScope.INSTANCE
 						.getNode(E4_THEME_EXTENSION_POINT);
-				userScopeNode.put("themeid", themeId); //$NON-NLS-1$
+				String productOrAppId = getProductOrApplicationId();
+				IEclipsePreferences scopedNode = productOrAppId != null
+						? (IEclipsePreferences) baseNode.node(productOrAppId)
+						: baseNode;
+				scopedNode.put("themeid", themeId); //$NON-NLS-1$
 				try {
-					userScopeNode.flush();
+					scopedNode.flush();
 				} catch (BackingStoreException e) {
 					WorkbenchPlugin.log("Failed to set default theme in user scope", e); //$NON-NLS-1$
 				}