Style workspace selection dialog with default theme setting

Author: vogella

bundles/org.eclipse.ui.ide.application/META-INF/MANIFEST.MF

@@ -19,7 +19,8 @@ Require-Bundle: org.eclipse.ui.ide;bundle-version="[3.21.0,4.0.0)",
  org.eclipse.e4.core.services;bundle-version="2.4.0",
  org.eclipse.e4.core.contexts;bundle-version="[1.12.0,2.0.0)",
  org.eclipse.urischeme;bundle-version="[1.3.0,2.0.0)",
- org.eclipse.e4.ui.di
+ org.eclipse.e4.ui.di,
+ org.eclipse.ui.forms
 Export-Package: org.eclipse.ui.internal.ide.application;x-internal:=true,
  org.eclipse.ui.internal.ide.application.addons;x-internal:=true,
  org.eclipse.ui.internal.ide.application.dialogs;x-internal:=true

bundles/org.eclipse.ui.ide.application/src/org/eclipse/ui/internal/ide/application/IDEApplication.java

@@ -42,6 +42,7 @@
 import org.eclipse.core.runtime.Status;
 import org.eclipse.core.runtime.jobs.Job;
 import org.eclipse.core.runtime.preferences.ConfigurationScope;
+import org.eclipse.core.runtime.preferences.IEclipsePreferences;
 import org.eclipse.equinox.app.IApplication;
 import org.eclipse.equinox.app.IApplicationContext;
 import org.eclipse.jface.dialogs.IDialogConstants;
@@ -53,7 +54,9 @@
 import org.eclipse.osgi.util.NLS;
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.layout.FillLayout;
+import org.eclipse.swt.graphics.Color;
 import org.eclipse.swt.widgets.Composite;
+import org.eclipse.ui.forms.widgets.ExpandableComposite;
 import org.eclipse.swt.widgets.Control;
 import org.eclipse.swt.widgets.Display;
 import org.eclipse.swt.widgets.Label;
@@ -94,6 +97,8 @@ public class IDEApplication implements IApplication, IExecutableExtension {
 
 	private static final String USER_NAME = "user.name"; //$NON-NLS-1$
 
+	private boolean isDarkTheme;
+
 	// Use the branding plug-in of the platform feature since this is most likely
 	// to change on an update of the IDE.
 	private static final String WORKSPACE_CHECK_REFERENCE_BUNDLE_NAME = "org.eclipse.platform"; //$NON-NLS-1$
@@ -145,6 +150,15 @@ public Object start(IApplicationContext appContext) throws Exception {
 		Job.getJobManager().suspend();
 
 		Display display = createDisplay();
+
+		IEclipsePreferences configurationScopeNode = ConfigurationScope.INSTANCE
+				.getNode("org.eclipse.e4.ui.css.swt.theme"); //$NON-NLS-1$
+		String defaultThemeId = configurationScopeNode.get("themeid", null); //$NON-NLS-1$
+		isDarkTheme = defaultThemeId != null && defaultThemeId.toLowerCase().contains("dark"); //$NON-NLS-1$
+		if (isDarkTheme) {
+			requestDarkWindowDecorations(display);
+		}
+
 		// processor must be created before we start event loop
 		DelayedEventsProcessor processor = new DelayedEventsProcessor(display);
 
@@ -587,9 +601,51 @@ protected Shell getParentShell() {
 				return null;
 			}
 
+			@Override
+			protected Control createContents(Composite parent) {
+				Control contents = super.createContents(parent);
+				if (isDarkTheme) {
+					applyDarkColors(getShell());
+				}
+				return contents;
+			}
 		}.prompt(force);
 	}
 
+	private static void requestDarkWindowDecorations(Display display) {
+		// On GTK, request dark window decorations via the SWT internal API.
+		// Use reflection to avoid a hard compile-time dependency on GTK internals.
+		if ("gtk".equals(SWT.getPlatform())) { //$NON-NLS-1$
+			try {
+				Class.forName("org.eclipse.swt.internal.gtk.OS") //$NON-NLS-1$
+						.getMethod("setDarkThemePreferred", boolean.class) //$NON-NLS-1$
+						.invoke(null, true);
+			} catch (ReflectiveOperationException e) {
+				// GTK OS API unavailable — ignore
+			}
+		}
+	}
+
+	private static void applyDarkColors(Shell shell) {
+		// Colors matching org-eclipse-ui-workbench-DARK_BACKGROUND / DARK_FOREGROUND
+		Color background = new Color(0x48, 0x48, 0x4c);
+		Color foreground = new Color(0xee, 0xee, 0xee);
+		applyColorsRecursively(shell, background, foreground);
+	}
+
+	private static void applyColorsRecursively(Control control, Color background, Color foreground) {
+		control.setBackground(background);
+		control.setForeground(foreground);
+		if (control instanceof ExpandableComposite expandable) {
+			expandable.setTitleBarForeground(foreground);
+		}
+		if (control instanceof Composite composite) {
+			for (Control child : composite.getChildren()) {
+				applyColorsRecursively(child, background, foreground);
+			}
+		}
+	}
+
 	/**
 	 * Result of the {@link IDEApplication#checkValidWorkspace(Shell, URL)}
 	 * operation