Restyle Copy Settings check buttons on macOS when section is shown

On macOS Cocoa, setBackground/setForeground applied to a widget that is
currently hidden is not retained once the widget is realized. The "Copy
Settings" section of ChooseWorkspaceWithSettingsDialog is created with
setVisible(false), so the theme-engine colors on its check buttons are
dropped and the buttons paint with the default light system colors when
the user expands the section on a dark theme.

Re-apply the parent background/foreground to the check buttons when the
section first becomes visible. Guarded with Util.isMac() since GTK and
Windows retain the colors across realize and do not need this workaround.

Fixes #3897

Author: vogella

bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/ChooseWorkspaceWithSettingsDialog.java

@@ -34,6 +34,7 @@
 import org.eclipse.jface.fieldassist.ControlDecoration;
 import org.eclipse.jface.fieldassist.FieldDecorationRegistry;
 import org.eclipse.jface.resource.JFaceResources;
+import org.eclipse.jface.util.Util;
 import org.eclipse.osgi.util.NLS;
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.custom.ScrolledComposite;
@@ -153,6 +154,20 @@ private void createSettingsControls(Composite workArea) {
 		clientData.exclude = !expanded;
 		toggle.setText(expanded ? "\u25BE" : "\u25B8"); //$NON-NLS-1$ //$NON-NLS-2$
 
+		// On macOS Cocoa, setBackground/setForeground on a hidden widget is dropped
+		// once the widget is realized. Re-apply colors to the check buttons when
+		// the section first becomes visible.
+		if (Util.isMac()) {
+			sectionClient.addListener(SWT.Show, e -> {
+				for (Control child : sectionClient.getChildren()) {
+					if (child instanceof Button button && (button.getStyle() & SWT.CHECK) != 0) {
+						button.setBackground(workArea.getBackground());
+						button.setForeground(workArea.getForeground());
+					}
+				}
+			});
+		}
+
 		Listener toggleListener = e -> {
 			boolean newState = !sectionClient.getVisible();
 			sectionClient.setVisible(newState);