Improved dark styling for buttons in workspace selection dialog

Skip the early dark-theme styling for Button controls in the workspace
selection dialog at startup so buttons get the native macOS dark
appearance instead, matching what the ThemeEngine applies later.

Other widgets (Shell, Composite, Label, Link, ExpandableComposite)
remain styled as before since the ThemeEngine is not yet available
during workspace selection.

On windows we still need to style the check buttons otherwise they look
white.

Fixes: #3905

Author: vogella

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

@@ -58,6 +58,7 @@
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.graphics.Color;
 import org.eclipse.swt.layout.FillLayout;
+import org.eclipse.swt.widgets.Button;
 import org.eclipse.swt.widgets.Composite;
 import org.eclipse.swt.widgets.Control;
 import org.eclipse.swt.widgets.Display;
@@ -952,6 +953,15 @@ private void applyDarkStyles(Shell shell) {
 	}
 
 	private void applyStylesRecursive(Control control, Color bg, Color fg, Color linkColor) {
+		if (control instanceof Button button) {
+			// On Windows, check buttons need an explicit background; otherwise they
+			// appear white because the parent background is not inherited.
+			if (Platform.OS_WIN32.equals(Platform.getOS()) && (button.getStyle() & SWT.CHECK) != 0) {
+				button.setBackground(bg);
+			}
+			// Leave other buttons unstyled so the native dark appearance is used
+			return;
+		}
 		control.setBackground(bg);
 		if (control instanceof Link link) {
 			link.setLinkForeground(linkColor);